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<!DOCTYPE html>
<html lang="en" data-theme="dark">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>JWT Debugger: Decode, Verify, Sign HMAC JWTs | Secutils.dev</title>
<meta name="description" content="Free JWT debugger. Decode, verify, and sign HMAC JSON Web Tokens (HS256, HS384, HS512) directly in your browser. State stays in the URL fragment. No signup.">
<meta name="robots" content="index, follow, max-image-preview:large">
<link rel="canonical" href="https://{{TOOLS_HOST}}/jwt">
<meta name="su-tool-path" content="/jwt">
<meta name="su-tool-name" content="JWT Debugger">
<meta name="su-tool-description" content="Decode, verify, and sign HMAC JSON Web Tokens (HS256, HS384, HS512). Real-time signature validation, shareable URL state, no signup.">
<meta name="su-tool-promote" content="true">
<meta property="og:type" content="website">
<meta property="og:site_name" content="Secutils.dev">
<meta property="og:title" content="JWT Debugger: Decode, Verify, Sign HMAC JWTs">
<meta property="og:description" content="Free JWT debugger. Decode, verify, and sign HMAC JSON Web Tokens (HS256, HS384, HS512) directly in your browser. State stays in the URL fragment.">
<meta property="og:url" content="https://{{TOOLS_HOST}}/jwt">
<meta property="og:image" content="https://secutils.dev/docs/img/og/og-jwt.png">
<meta property="og:image:width" content="1200">
<meta property="og:image:height" content="630">
<meta property="og:image:alt" content="JWT Debugger on Secutils.dev: decode, verify, sign HMAC JSON Web Tokens.">
<meta property="og:locale" content="en_US">
<meta name="twitter:card" content="summary_large_image">
<meta name="twitter:title" content="JWT Debugger: Decode, Verify, Sign HMAC JWTs">
<meta name="twitter:description" content="Free JWT debugger. Decode, verify, and sign HMAC JSON Web Tokens directly in your browser. No signup.">
<meta name="twitter:image" content="https://secutils.dev/docs/img/og/og-jwt.png">
<script type="application/ld+json">{"@context":"https://schema.org","@type":"WebApplication","name":"JWT Debugger","url":"https://{{TOOLS_HOST}}/jwt","applicationCategory":"SecurityApplication","operatingSystem":"Any","browserRequirements":"Requires JavaScript","isAccessibleForFree":true,"offers":{"@type":"Offer","price":"0","priceCurrency":"USD"},"publisher":{"@type":"Organization","name":"Secutils.dev","url":"https://secutils.dev"},"sameAs":"https://github.com/secutils-dev/secutils/blob/main/dev/tools/jwt-debugger.html","description":"Free JWT debugger. Decode, verify, and sign HMAC JSON Web Tokens (HS256, HS384, HS512) directly in your browser. State stays in the URL fragment so tokens never leave your machine."}</script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jose/4.14.4/index.umd.min.js" integrity="sha384-poiEbfNKlGsC2UCQ/2tTuNE0fFy0BsCXn1io3SyuDm7TqWh8EgorXSCmzu8UE4rD" crossorigin="anonymous" defer fetchpriority="low"></script>
<link rel="preconnect" href="https://fonts.googleapis.com">
<link rel="preconnect" href="https://fonts.gstatic.com" crossorigin>
<link href="https://fonts.googleapis.com/css2?family=Inter:wght@300..700&family=Roboto+Mono:wght@400..700&display=swap" rel="stylesheet">
<!-- Privacy-friendly analytics by Plausible -->
<script defer src="https://tools.secutils.dev/js/script.js" fetchpriority="low"></script>
<script>
window.plausible = window.plausible || function () { (plausible.q = plausible.q || []).push(arguments) };
plausible.init = plausible.init || function (i) { plausible.o = i || {} };
plausible.init();
</script>
<style>
:root, [data-theme="dark"] {
--bg: #141519;
--surface: #1d1e24;
--surface-hover: #2c2d33;
--border: #343741;
--text: #dfe5ef;
--text-muted: #98a2b3;
--primary: #fed047;
--primary-hover: #fdc615;
--primary-text: #642340;
--accent: #642340;
--badge-bg: #2B394F;
--badge-text: #98A8C3;
--header-color: #fb7185;
--payload-color: #c084fc;
--signature-color: #60a5fa;
--input-bg: #25262c;
--input-border: #343741;
--focus-ring: #fed047;
--success-bg: rgba(16,185,129,0.15);
--success-text: #6ee7b7;
--error-bg: rgba(239,68,68,0.15);
--error-text: #fca5a5;
--radius: 8px;
--font: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
--mono: 'Roboto Mono', 'SF Mono', 'Fira Code', Consolas, monospace;
}
[data-theme="light"] {
--bg: #f5f7fa;
--surface: #ffffff;
--surface-hover: #f1f3f5;
--border: #d3dae6;
--text: #343741;
--text-muted: #69707d;
--primary: #fed047;
--primary-hover: #fdc615;
--primary-text: #642340;
--accent: #642340;
--badge-bg: #E3E8F2;
--badge-text: #505F79;
--header-color: #e11d48;
--payload-color: #9333ea;
--signature-color: #2563eb;
--input-bg: #f5f7fa;
--input-border: #d3dae6;
--focus-ring: #642340;
--success-bg: rgba(16,185,129,0.1);
--success-text: #059669;
--error-bg: rgba(239,68,68,0.1);
--error-text: #dc2626;
}
*, *::before, *::after { box-sizing: border-box; }
body { font-family: var(--font); background: var(--bg); color: var(--text); margin: 0; min-height: 100vh; display: flex; flex-direction: column; transition: background .3s, color .3s; }
/* Header */
header { height: 48px; padding: 0 16px; background: var(--surface); border-bottom: 1px solid var(--border); position: sticky; top: 0; z-index: 100; display: flex; align-items: center; justify-content: space-between; transition: background .25s, border-color .25s; }
.header-left { display: flex; align-items: center; gap: 12px; }
.logo { display: flex; align-items: center; text-decoration: none; }
.logo-svg .logo-text-fill { fill: var(--text); }
.logo-badge { display: inline-flex; align-items: center; padding: 4px 16px; border-radius: 4px; border: none; background: var(--badge-bg); color: var(--badge-text); font-size: 12px; font-weight: 450; line-height: 16px; white-space: nowrap; }
.header-right { display: flex; align-items: center; gap: 8px; }
.skill-link { height: 36px; display: inline-flex; align-items: center; gap: 6px; padding: 0 12px; border: 1px solid var(--border); border-radius: 18px; background: var(--surface); color: var(--text-muted); font: 12px var(--font); text-decoration: none; transition: all .15s; cursor: pointer; }
.skill-link:hover { color: var(--text); border-color: var(--text-muted); background: var(--surface-hover); }
.skill-link svg { width: 14px; height: 14px; fill: none; stroke: currentColor; }
/* Theme toggle */
.theme-toggle { width: 36px; height: 36px; padding: 0; display: flex; align-items: center; justify-content: center; border-radius: 50%; border: 1px solid var(--border); background: var(--surface); color: var(--text-muted); cursor: pointer; transition: all .2s; }
.theme-toggle:hover { background: var(--surface-hover); color: var(--text); }
.theme-toggle svg { width: 16px; height: 16px; fill: currentColor; }
.theme-toggle .icon-sun { display: none; }
.theme-toggle .icon-moon { display: block; }
[data-theme="dark"] .theme-toggle .icon-sun { display: block; }
[data-theme="dark"] .theme-toggle .icon-moon { display: none; }
/* Noscript banner */
.su-noscript { max-width: 720px; margin: 24px auto; padding: 16px; border: 1px solid var(--border); border-radius: 8px; font: 14px/1.5 var(--font); background: var(--surface); color: var(--text); }
/* Main + grid */
main { flex: 1; padding: 24px 16px; display: flex; flex-direction: column; max-width: 1400px; width: 100%; margin: 0 auto; }
.grid { display: grid; grid-template-columns: 1fr 12px 1fr; gap: 0; flex: 1; min-height: 0; }
.panel { display: flex; flex-direction: column; min-height: 0; }
.panel-bar { display: flex; align-items: center; justify-content: space-between; padding: 0 0 8px; gap: 8px; height: 38px; box-sizing: content-box; flex-shrink: 0; }
.panel-actions { display: flex; align-items: center; gap: 8px; }
.panel-label { font-size: 13px; font-weight: 600; color: var(--text); }
.link-btn { border: none; background: none; font: 12px var(--font); color: var(--text-muted); cursor: pointer; padding: 2px 4px; transition: color .15s; }
.link-btn:hover { color: var(--text); }
/* Buttons */
/* `height` pins the outer size so `.btn-primary`'s `font-weight: 600` doesn't
render 1-2 px taller than the regular variant via expanded bold strut
metrics. See dev/tools/guides/chrome.md -> "Buttons". */
.btn { padding: 7px 14px; height: 29px; border-radius: 8px; border: 1px solid var(--border); background: var(--surface); color: var(--text); font: 13px/1 var(--font); cursor: pointer; transition: all .15s; display: inline-flex; align-items: center; gap: 5px; white-space: nowrap; }
.btn:hover:not(:disabled) { background: var(--surface-hover); border-color: var(--text-muted); }
.btn-primary { background: var(--primary); border-color: var(--primary-text); color: var(--primary-text); font-weight: 500; }
.btn-primary:hover:not(:disabled) { background: var(--primary-hover); border-color: var(--primary-hover); }
.btn-sm { padding: 5px 10px; height: 24px; font-size: 12px; }
.icon-btn { padding: 4px; border: none; background: none; color: var(--text-muted); cursor: pointer; border-radius: 4px; transition: all .15s; display: inline-flex; align-items: center; justify-content: center; }
.icon-btn:hover { color: var(--text); background: var(--surface-hover); }
.icon-btn svg { width: 16px; height: 16px; }
/* Encoded pane */
.encoded-area { flex: 1; min-height: 400px; padding: 14px; background: var(--input-bg); border: 1px solid var(--input-border); border-radius: var(--radius); font: 0.875rem/1.6 var(--mono); color: var(--text); white-space: pre-wrap; word-break: break-all; outline: none; overflow: auto; transition: border-color .15s, background .25s, color .25s; }
.encoded-area:focus { border-color: var(--focus-ring); }
.encoded-area:empty::before { content: attr(data-placeholder); color: var(--text-muted); }
.token-part-header { color: var(--header-color); }
.token-part-payload { color: var(--payload-color); }
.token-part-signature { color: var(--signature-color); }
.token-dot { color: var(--text-muted); }
/* Transform info banner (above the encoded area when prefix is stripped) */
.transform-info { margin-bottom: 8px; padding: 8px 12px; border-radius: 8px; background: var(--badge-bg); color: var(--badge-text); font-size: 0.8rem; line-height: 1.4; }
.transform-info code { font-family: var(--mono); font-size: 0.75rem; background: var(--input-bg); padding: 1px 5px; border-radius: 3px; }
/* Algorithm select (compact, lives in the left panel-bar) */
.algo-select { background: var(--input-bg); border: 1px solid var(--input-border); border-radius: 6px; padding: 4px 10px; color: var(--text); font: 12px var(--font); cursor: pointer; transition: border-color .15s; }
.algo-select:focus { outline: none; border-color: var(--focus-ring); }
/* Decoded pane */
.decoded-stack { flex: 1; display: flex; flex-direction: column; gap: 16px; min-height: 0; overflow-y: auto; padding-right: 4px; position: relative; }
.card { background: var(--surface); border: 1px solid var(--border); border-radius: 12px; overflow: hidden; transition: background .25s, border-color .25s; display: flex; flex-direction: column; }
.card-header { padding: 10px 14px; border-bottom: 1px solid var(--border); font-weight: 600; font-size: 0.75rem; text-transform: uppercase; letter-spacing: 0.5px; }
.card-body { padding: 12px 14px; }
/* The last card (Verify Signature) absorbs any leftover vertical space so the
stack doesn't end with a gap below it on tall viewports. */
.verify-card { flex: 1; min-height: 200px; }
.verify-card .card-body { flex: 1; display: flex; flex-direction: column; gap: 12px; }
.verify-card #secret-input { flex: 1; min-height: 80px; }
.verify-card #signature-status { margin-top: 0; }
/* View tabs (segmented pill) - same as saml-decoder */
.view-tabs { display: inline-flex; gap: 2px; padding: 2px; background: var(--input-bg); border: 1px solid var(--border); border-radius: 6px; }
.view-tab { padding: 3px 10px; border: none; background: transparent; color: var(--text-muted); font: 12px/1 var(--font); font-weight: 500; cursor: pointer; border-radius: 4px; transition: all .15s; }
.view-tab:hover { color: var(--text); }
.view-tab.active { background: var(--surface-hover); color: var(--text); font-weight: 600; }
.tab-content { display: none; }
.tab-content.active { display: block; }
/* JSON editors inside cards */
.json-editor { width: 100%; min-height: 140px; padding: 10px 12px; border: 1px solid var(--input-border); border-radius: var(--radius); background: var(--input-bg); color: var(--text); font: 0.875rem/1.5 var(--mono); resize: vertical; outline: none; transition: border-color .15s; }
.json-editor:focus { border-color: var(--focus-ring); }
.json-editor.invalid { border-color: var(--error-text); }
/* Claims table */
.claims-table { width: 100%; border-collapse: collapse; }
.claims-table td { padding: 6px 8px; border-bottom: 1px solid var(--border); font: 0.8rem/1.4 var(--mono); vertical-align: top; }
.claims-table tr:last-child td { border-bottom: none; }
.claims-table td:first-child { color: var(--text-muted); white-space: nowrap; }
.claims-table td:last-child { color: var(--text); word-break: break-word; }
.claims-desc { font-size: 0.7rem; color: var(--text-muted); display: block; margin-top: 2px; font-family: var(--font); }
/* Verify Signature card */
#secret-input { width: 100%; min-height: 80px; padding: 10px 12px; border: 1px solid var(--input-border); border-radius: var(--radius); background: var(--input-bg); color: var(--text); font: 0.875rem/1.5 var(--mono); resize: vertical; outline: none; transition: border-color .15s; }
#secret-input:focus { border-color: var(--focus-ring); }
#signature-status { margin-top: 12px; text-align: center; font-weight: 600; padding: 8px 16px; border-radius: var(--radius); font-size: 0.875rem; min-height: 32px; }
.sig-valid { background: var(--success-bg); color: var(--success-text); }
.sig-invalid { background: var(--error-bg); color: var(--error-text); }
/* Parse error overlay (above decoded stack when JWT can't be parsed) */
.parse-error-overlay { padding: 28px 24px; border: 1px dashed var(--error-text); border-radius: 12px; background: var(--error-bg); color: var(--error-text); font-size: 0.9rem; line-height: 1.5; text-align: center; }
.parse-error-overlay::before { content: ''; display: block; width: 36px; height: 36px; margin: 0 auto 12px; border-radius: 50%; background: var(--error-bg); background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 16 16'%3E%3Cpath d='M8 1a7 7 0 1 1 0 14A7 7 0 0 1 8 1Zm0 1a6 6 0 1 0 0 12A6 6 0 0 0 8 2Zm0 3a.5.5 0 0 1 .5.5v3a.5.5 0 0 1-1 0v-3A.5.5 0 0 1 8 5Zm0 5.5a.75.75 0 1 1 0 1.5.75.75 0 0 1 0-1.5Z' fill='%23fca5a5'/%3E%3C/svg%3E"); background-repeat: no-repeat; background-position: center; background-size: 22px; }
[data-theme="light"] .parse-error-overlay::before { background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 16 16'%3E%3Cpath d='M8 1a7 7 0 1 1 0 14A7 7 0 0 1 8 1Zm0 1a6 6 0 1 0 0 12A6 6 0 0 0 8 2Zm0 3a.5.5 0 0 1 .5.5v3a.5.5 0 0 1-1 0v-3A.5.5 0 0 1 8 5Zm0 5.5a.75.75 0 1 1 0 1.5.75.75 0 0 1 0-1.5Z' fill='%23dc2626'/%3E%3C/svg%3E"); }
/* Splitter */
.splitter { cursor: col-resize; background: transparent; position: relative; z-index: 1; }
.splitter::after { content: ''; position: absolute; top: 0; bottom: 0; left: 50%; width: 1px; background: var(--border); transition: width .15s, background .15s; transform: translateX(-50%); }
.splitter:hover::after, .splitter.active::after { width: 3px; background: var(--primary); border-radius: 2px; }
.splitter-overlay { position: fixed; inset: 0; z-index: 9999; cursor: col-resize; }
/* Fullscreen the right (decoded) pane */
#decodedPane:fullscreen { background: var(--bg); padding: 16px; display: flex; flex-direction: column; overflow: hidden; }
#decodedPane:fullscreen .decoded-stack { flex: 1; min-height: 0; }
/* "More free tools" CTA */
.su-more-tools { margin: 16px 0 0; padding: 12px 18px; text-align: center; border: 1px solid rgba(254, 208, 71, 0.35); border-radius: 12px; background: rgba(254, 208, 71, 0.06); font: 13px/1.55 var(--font); color: var(--text); transition: border-color .25s, background-color .25s, color .25s; }
.su-more-tools p { margin: 0; }
.su-more-tools a { color: var(--primary); font-weight: 700; text-decoration: none; white-space: nowrap; }
.su-more-tools a:hover { color: var(--primary-hover); text-decoration: underline; }
/* Footer */
.su-footer { text-align: center; padding: 16px; border-top: 1px solid var(--border); color: var(--text-muted); font-size: 0.8rem; transition: border-color .25s, color .25s; }
.su-footer p { margin: 0; }
.su-footer-fineprint { margin-top: 6px !important; font-size: 0.7rem; opacity: 0.75; }
.su-footer-link { background: none; border: none; padding: 0; color: inherit; font: inherit; cursor: pointer; text-decoration: underline; text-underline-offset: 2px; }
.su-footer-link:hover { color: var(--text); }
.su-dialog { max-width: 520px; width: calc(100% - 32px); max-height: calc(100% - 32px); inset: 0; margin: auto; padding: 0; border: 1px solid var(--border); border-radius: 12px; background: var(--surface); color: var(--text); box-shadow: 0 20px 60px rgba(0,0,0,0.4); }
.su-dialog::backdrop { background: rgba(0,0,0,0.45); backdrop-filter: blur(2px); }
.su-dialog-header { display: flex; align-items: center; justify-content: space-between; padding: 14px 18px; border-bottom: 1px solid var(--border); }
.su-dialog-header h2 { font-size: 1rem; font-weight: 600; }
.su-dialog-close { width: 28px; height: 28px; padding: 0; display: flex; align-items: center; justify-content: center; border-radius: 50%; border: 1px solid var(--border); background: var(--surface); color: var(--text-muted); cursor: pointer; transition: all .15s; }
.su-dialog-close:hover { background: var(--surface-hover); color: var(--text); }
.su-dialog-body { padding: 16px 18px; font-size: 0.875rem; line-height: 1.55; color: var(--text); }
.su-dialog-body p { margin-bottom: 12px; }
.su-dialog-body p:last-child { margin-bottom: 0; }
.su-dialog-body code { font-family: var(--mono); background: var(--surface-hover); padding: 1px 5px; border-radius: 4px; font-size: 0.85em; }
.su-dialog-body a { color: var(--primary); text-decoration: none; }
.su-dialog-body a:hover { text-decoration: underline; }
.su-dialog-fineprint { font-size: 0.8rem; color: var(--text-muted); }
/* Typography polish (Baseline; selectors that don't exist in this tool are no-ops). See dev/tools/guides/chrome.md → "Typography polish". */
.page-title, .panel-label, .su-dialog-header h2, .card-header { text-wrap: balance; }
.su-dialog-body p, .su-more-tools p, .tool-desc, .empty-state-sub, .progress-sub, .error-sub { text-wrap: pretty; }
/* Respect prefers-reduced-motion. See dev/tools/guides/chrome.md → "Reduced motion". */
@media (prefers-reduced-motion: reduce) {
*, *::before, *::after { animation-duration: 0.01ms !important; animation-iteration-count: 1 !important; transition-duration: 0.01ms !important; scroll-behavior: auto !important; }
}
.su-credits-list { margin: 0 0 12px; padding-left: 20px; }
.su-credits-list li { margin-bottom: 6px; }
.su-credits-list li:last-child { margin-bottom: 0; }
/* Toast */
.toast { position: fixed; bottom: 20px; right: 20px; background: var(--surface); color: var(--text); padding: 10px 18px; border-radius: 8px; border: 1px solid var(--border); font-size: 13px; z-index: 200; box-shadow: 0 4px 12px rgba(0,0,0,0.3); display: flex; align-items: center; gap: 8px; animation: toastIn .2s ease; }
@keyframes toastIn { from { opacity: 0; transform: translateY(8px); } to { opacity: 1; transform: translateY(0); } }
/* Scrollbar */
::-webkit-scrollbar { width: 8px; height: 8px; }
::-webkit-scrollbar-track { background: var(--bg); }
::-webkit-scrollbar-thumb { background: var(--border); border-radius: 4px; }
::-webkit-scrollbar-thumb:hover { background: var(--text-muted); }
/* Responsive */
@media (max-width: 900px) {
.grid { grid-template-columns: 1fr; row-gap: 24px; }
.splitter { display: none; }
.encoded-area { min-height: 240px; }
.decoded-stack { overflow-y: visible; padding-right: 0; }
.panel-bar { flex-wrap: wrap; row-gap: 8px; height: auto; min-height: 38px; }
.panel-actions { flex-wrap: wrap; justify-content: flex-end; }
}
@media (max-width: 600px) { .su-more-tools { padding: 12px 14px; } .su-more-tools a { white-space: normal; } }
@media (max-width: 640px) {
header { padding: 0 12px; }
.logo-svg { height: 20px; }
.logo-badge { font-size: 11px; padding: 2px 7px; }
main { padding: 16px 12px; }
.btn { padding: 6px 10px; font-size: 12px; }
.skill-link span { display: none; }
.skill-link { padding: 0 10px; }
.algo-select { padding: 4px 8px; font-size: 11px; }
}
</style>
</head>
<body>
<noscript>
<p class="su-noscript"><strong>JWT Debugger</strong> — Decode, verify, and sign HMAC JSON Web Tokens (HS256, HS384, HS512) directly in your browser. Tokens stay in the URL fragment and never reach the server. This tool requires JavaScript; please enable it. Source on <a href="https://github.com/secutils-dev/secutils/blob/main/dev/tools/jwt-debugger.html">GitHub</a>.</p>
</noscript>
<header>
<div class="header-left">
<a class="logo" href="https://secutils.dev" target="_blank" rel="noopener">
<svg class="logo-svg" height="24" role="img" viewBox="0 0 98 16" xmlns="http://www.w3.org/2000/svg">
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</svg>
</a>
<span class="logo-badge">JWT Debugger</span>
</div>
<div class="header-right">
<a id="skillLink" class="skill-link" href="#" target="_blank" rel="noopener"
title="View AI agent skill (skill.md, opens in new tab)"
aria-label="View AI agent skill (opens in new tab)">
<svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" aria-hidden="true">
<path d="M9.937 15.5A2 2 0 0 0 8.5 14.063l-6.135-1.582a.5.5 0 0 1 0-.962L8.5 9.936A2 2 0 0 0 9.937 8.5l1.582-6.135a.5.5 0 0 1 .963 0L14.063 8.5A2 2 0 0 0 15.5 9.937l6.135 1.582a.5.5 0 0 1 0 .962L15.5 14.063a2 2 0 0 0-1.437 1.437l-1.582 6.135a.5.5 0 0 1-.963 0z"/>
<path d="M20 3v4"/><path d="M22 5h-4"/><path d="M4 17v2"/><path d="M5 18H3"/>
</svg>
<span>Skill</span>
</a>
<button class="theme-toggle" id="themeToggle" aria-label="Toggle theme">
<svg class="icon-sun" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 16 16"><path d="M8.5 15h-1v-2h1v2Zm-3.674-3.107-1.414 1.414-.707-.707 1.414-1.415.707.708Zm8.479.707-.707.707-1.414-1.414.707-.708 1.414 1.415Z"/><path fill-rule="evenodd" d="M8 4a4 4 0 1 1 0 8 4 4 0 0 1 0-8Zm0 1a3 3 0 1 0 0 6 3 3 0 0 0 0-6Z" clip-rule="evenodd"/><path d="M3.005 8.505h-2v-1h2v1Zm12 0h-2v-1h2v1ZM4.82 4.114l-.708.707-1.414-1.414.707-.707L4.82 4.114Zm8.492-.707-1.414 1.414-.708-.707L12.605 2.7l.707.707ZM8.5 3h-1V1h1v2Z"/></svg>
<svg class="icon-moon" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 16 16"><path d="M4.05 12.95A6.982 6.982 0 0 1 2 8c0-1.79.684-3.583 2.05-4.95A6.982 6.982 0 0 1 9 1a1 1 0 0 1 .708 1.707 4.982 4.982 0 0 0-1.465 3.536 4.98 4.98 0 0 0 1.465 3.535 4.98 4.98 0 0 0 3.535 1.465 1 1 0 0 1 .707 1.707A6.981 6.981 0 0 1 9 15a6.983 6.983 0 0 1-4.95-2.05Zm.708-.707A5.983 5.983 0 0 0 9 14c1.535 0 3.07-.586 4.242-1.757a5.98 5.98 0 0 1-4.018-1.545L9 10.485a5.982 5.982 0 0 1-1.758-4.242A5.986 5.986 0 0 1 9 2a5.983 5.983 0 0 0-4.243 1.757A5.98 5.98 0 0 0 3 8l.006.288a5.978 5.978 0 0 0 1.75 3.955Z"/></svg>
</button>
</div>
</header>
<main>
<div class="grid">
<!-- Encoded pane -->
<div class="panel">
<div class="panel-bar">
<span class="panel-label">Encoded</span>
<div class="panel-actions">
<select id="algorithm-select" class="algo-select" aria-label="Algorithm">
<option>HS256</option>
<option>HS384</option>
<option>HS512</option>
<option disabled>--- RS/ES/PS algorithms require key pairs ---</option>
</select>
<button class="link-btn" id="exampleBtn">Example</button>
<button class="link-btn" id="clearBtn">Clear</button>
<button id="share-button" class="btn btn-primary btn-sm" title="Copy a shareable link with the JWT and secret encoded in the URL">Share</button>
</div>
</div>
<div id="transform-info" class="transform-info" style="display:none"></div>
<div id="encoded-output" contenteditable="true" spellcheck="false" class="encoded-area" data-placeholder="Paste a JWT (header.payload.signature). Bearer prefixes and base64-wrapped tokens are unwrapped automatically." aria-label="Encoded JWT"></div>
</div>
<div class="splitter" id="splitter"></div>
<!-- Decoded pane -->
<div id="decodedPane" class="panel">
<div class="panel-bar">
<div class="view-tabs" id="view-tabs" role="tablist" aria-label="Decoded view (applies to header and payload)">
<button class="view-tab active" data-view="json" role="tab" aria-selected="true" title="Show JSON editors">JSON</button>
<button class="view-tab" data-view="table" role="tab" aria-selected="false" title="Show claim tables">Table</button>
</div>
<div class="panel-actions">
<button id="copy-button" class="btn btn-sm" title="Copy the encoded token to your clipboard">
<svg viewBox="0 0 16 16" width="14" height="14" fill="none" stroke="currentColor" stroke-width="1.6" stroke-linecap="round" stroke-linejoin="round" aria-hidden="true"><rect x="4" y="4" width="9" height="10" rx="1.5"/><path d="M3 11V3.5A1.5 1.5 0 0 1 4.5 2H10"/></svg>
<span class="btn-label">Copy</span>
</button>
<button id="fullscreenBtn" class="icon-btn" title="Toggle fullscreen" aria-label="Toggle fullscreen">
<svg id="fullscreenEnterIcon" xmlns="http://www.w3.org/2000/svg" width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><path d="M8 3H5a2 2 0 0 0-2 2v3m18 0V5a2 2 0 0 0-2-2h-3m0 18h3a2 2 0 0 0 2-2v-3M3 16v3a2 2 0 0 0 2 2h3"/></svg>
<svg id="fullscreenExitIcon" xmlns="http://www.w3.org/2000/svg" width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" style="display:none"><path d="M8 3v3a2 2 0 0 1-2 2H3m18 0h-3a2 2 0 0 1-2-2V3m0 18v-3a2 2 0 0 1 2-2h3M3 16h3a2 2 0 0 1 2 2v3"/></svg>
</button>
</div>
</div>
<div class="decoded-stack">
<div id="parse-error" class="parse-error-overlay" style="display:none"></div>
<!-- Header card -->
<div class="card">
<div class="card-header" style="color: var(--header-color);">Header: Algorithm & Token Type</div>
<div class="card-body" id="header-tab-content"></div>
</div>
<!-- Payload card -->
<div class="card">
<div class="card-header" style="color: var(--payload-color);">Payload: Data</div>
<div class="card-body" id="payload-tab-content"></div>
</div>
<!-- Verify Signature card (grows to fill remaining vertical space) -->
<div class="card verify-card">
<div class="card-header" style="color: var(--signature-color);">Verify Signature</div>
<div class="card-body">
<textarea id="secret-input" spellcheck="false" placeholder="Your-256-bit-secret"></textarea>
<div id="signature-status"></div>
</div>
</div>
</div>
</div>
</div>
<aside class="su-more-tools" aria-label="More free tools">
<p>Other free, no-signup Secutils.dev tools for SAML, certificates, Markdown, HTTP echo, and more - <a href="https://{{TOOLS_HOST}}/">Browse all tools →</a></p>
</aside>
</main>
<footer class="su-footer">
<p>A single-file JWT debugger for decoding, verifying, and signing JSON Web Tokens.</p>
<p class="su-footer-fineprint">
<button type="button" class="su-footer-link" id="privacyOpen">Privacy</button>
<span aria-hidden="true"> · </span>
<button type="button" class="su-footer-link" id="creditsOpen">Credits</button>
</p>
</footer>
<dialog id="privacyDialog" class="su-dialog" closedby="any" aria-labelledby="privacyDialogTitle">
<header class="su-dialog-header">
<h2 id="privacyDialogTitle">Privacy</h2>
<button type="button" class="su-dialog-close" id="privacyClose" aria-label="Close">
<svg viewBox="0 0 16 16" width="14" height="14" fill="none" stroke="currentColor" stroke-width="1.8" stroke-linecap="round" stroke-linejoin="round" aria-hidden="true"><path d="M3 3l10 10M13 3L3 13"/></svg>
</button>
</header>
<div class="su-dialog-body">
<p><strong>Your data stays in your browser.</strong> These tools run entirely client-side. Tokens, PEMs, SAML payloads, Markdown source, and mock-response bodies are never sent to the Secutils.dev server. State that needs to survive a reload (or be shared) lives in the URL fragment (<code>#…</code>), which browsers never transmit to the server.</p>
<p><strong>Anonymous usage analytics.</strong> We use <a href="https://plausible.io/" target="_blank" rel="noopener noreferrer">Plausible Analytics</a>, a privacy-first, GDPR-compliant tool, to collect aggregate usage data. No cookies, no personal data, no individual tracking. The data is limited to top pages, referral sources, visit duration, and device-class metadata (device type, OS, country, browser). Full details in the <a href="https://plausible.io/data-policy" target="_blank" rel="noopener noreferrer">Plausible Data Policy</a>.</p>
<p class="su-dialog-fineprint">See the full <a href="https://secutils.dev/privacy" target="_blank" rel="noopener noreferrer">Secutils.dev privacy policy</a> for details on the wider service.</p>
</div>
</dialog>
<dialog id="creditsDialog" class="su-dialog" closedby="any" aria-labelledby="creditsDialogTitle">
<header class="su-dialog-header">
<h2 id="creditsDialogTitle">Credits</h2>
<button type="button" class="su-dialog-close" id="creditsClose" aria-label="Close">
<svg viewBox="0 0 16 16" width="14" height="14" fill="none" stroke="currentColor" stroke-width="1.8" stroke-linecap="round" stroke-linejoin="round" aria-hidden="true"><path d="M3 3l10 10M13 3L3 13"/></svg>
</button>
</header>
<div class="su-dialog-body">
<p>This tool is powered by the following open-source libraries:</p>
<ul class="su-credits-list">
<li><a href="https://github.com/panva/jose" target="_blank" rel="noopener noreferrer"><strong>jose</strong></a> - JSON Object Signing and Encryption for the Web Crypto API, used to decode, verify, and sign JWTs.</li>
</ul>
<p class="su-dialog-fineprint">All trademarks are property of their respective owners.</p>
</div>
</dialog>
<div id="toast" class="toast" role="status" aria-live="polite" style="display:none">
<span id="toastMsg"></span>
</div>
<script>
(function() {
const skillLinkEl = document.getElementById('skillLink');
if (skillLinkEl) {
const p = location.pathname;
skillLinkEl.href = (p === '/' || p === '') ? '/llms.txt' : p.replace(/\/$/, '') + '.md';
}
const toggle = document.getElementById('themeToggle');
const root = document.documentElement;
const setTheme = (t) => {
root.setAttribute('data-theme', t);
try { localStorage.setItem('su-tool-theme', t); } catch (e) {}
};
toggle.addEventListener('click', () => {
setTheme(root.getAttribute('data-theme') === 'dark' ? 'light' : 'dark');
});
try {
const saved = localStorage.getItem('su-tool-theme');
if (saved) setTheme(saved);
else if (window.matchMedia('(prefers-color-scheme: light)').matches) setTheme('light');
} catch (e) {}
})();
(() => {
const dlg = document.getElementById('privacyDialog');
document.getElementById('privacyOpen').addEventListener('click', () => dlg.showModal());
document.getElementById('privacyClose').addEventListener('click', () => dlg.close());
})();
(() => {
const dlg = document.getElementById('creditsDialog');
document.getElementById('creditsOpen').addEventListener('click', () => dlg.showModal());
document.getElementById('creditsClose').addEventListener('click', () => dlg.close());
})();
// Safari fallback for closedby="any" (Newly Baseline elsewhere; limited in Safari as of Q2 2026).
if (!('closedBy' in HTMLDialogElement.prototype)) {
for (const dlg of document.querySelectorAll('dialog.su-dialog')) {
dlg.addEventListener('click', (e) => {
if (e.target !== dlg) return;
const r = dlg.getBoundingClientRect();
if (e.clientX < r.left || e.clientX > r.right || e.clientY < r.top || e.clientY > r.bottom) dlg.close();
});
}
}
// URL state encoding: see dev/tools/guides/url-state.md → "URL state encoding".
const utf8Enc = new TextEncoder();
const utf8Dec = new TextDecoder();
const toBase64Url = (bytes) => {
let s = '';
for (const b of bytes) s += String.fromCharCode(b);
return btoa(s).replace(/\+/g, '-').replace(/\//g, '_').replace(/=+$/, '');
};
const fromBase64UrlBytes = (str) => {
const b64 = str.replace(/-/g, '+').replace(/_/g, '/');
const padded = b64 + '==='.slice(0, (4 - b64.length % 4) % 4);
const bin = atob(padded);
const out = new Uint8Array(bin.length);
for (let i = 0; i < bin.length; i++) out[i] = bin.charCodeAt(i);
return out;
};
const encodeState = async (text) => {
const bytes = utf8Enc.encode(text);
const stream = new Blob([bytes]).stream().pipeThrough(new CompressionStream('deflate-raw'));
const deflated = new Uint8Array(await new Response(stream).arrayBuffer());
const out = new Uint8Array(4 + deflated.length);
new DataView(out.buffer).setUint32(0, bytes.length, true);
out.set(deflated, 4);
return toBase64Url(out);
};
const decodeState = async (str) => {
try {
const bytes = fromBase64UrlBytes(str);
if (bytes.length < 4) return null;
const stream = new Blob([bytes.subarray(4)]).stream()
.pipeThrough(new DecompressionStream('deflate-raw'));
const inflated = new Uint8Array(await new Response(stream).arrayBuffer());
return utf8Dec.decode(inflated);
} catch { return null; }
};
document.addEventListener('DOMContentLoaded', () => {
const algorithmSelect = document.getElementById('algorithm-select');
const encodedOutput = document.getElementById('encoded-output');
const secretInput = document.getElementById('secret-input');
const signatureStatus = document.getElementById('signature-status');
const copyButton = document.getElementById('copy-button');
const shareButton = document.getElementById('share-button');
const exampleBtn = document.getElementById('exampleBtn');
const clearBtn = document.getElementById('clearBtn');
const fullscreenBtn = document.getElementById('fullscreenBtn');
const fullscreenEnterIcon = document.getElementById('fullscreenEnterIcon');
const fullscreenExitIcon = document.getElementById('fullscreenExitIcon');
const decodedPane = document.getElementById('decodedPane');
const transformInfo = document.getElementById('transform-info');
const parseError = document.getElementById('parse-error');
const toastEl = document.getElementById('toast');
const toastMsgEl = document.getElementById('toastMsg');
let toastTimer;
const toast = (msg) => {
toastMsgEl.textContent = msg;
toastEl.style.display = 'flex';
clearTimeout(toastTimer);
toastTimer = setTimeout(() => { toastEl.style.display = 'none'; }, 2000);
};
const defaultState = {
header: { alg: 'HS256', typ: 'JWT' },
payload: { sub: '1234567890', name: 'John Doe', iat: Math.floor(Date.now() / 1000) },
secret: 'your-secret-key'
};
const JWT_CLAIMS = {
iss: '(Issuer) Claim', sub: '(Subject) Claim', aud: '(Audience) Claim',
exp: '(Expiration Time) Claim', nbf: '(Not Before) Claim', iat: '(Issued At) Claim', jti: '(JWT ID) Claim'
};
const base64UrlDecode = (str) => {
str = str.replace(/-/g, '+').replace(/_/g, '/');
while (str.length % 4) { str += '='; }
try { return decodeURIComponent(escape(atob(str))); } catch (e) { return null; }
};
const isValidJWT = (str) => {
const parts = str.split('.');
if (parts.length !== 3) return false;
if (!parts.every(p => p.length > 0 && /^[A-Za-z0-9_-]+$/.test(p))) return false;
try {
const header = JSON.parse(base64UrlDecode(parts[0]));
return header && typeof header === 'object' && ('alg' in header || 'typ' in header);
} catch (e) { return false; }
};
const tryBase64DecodeBytes = (str) => {
let padded = str.replace(/-/g, '+').replace(/_/g, '/');
while (padded.length % 4) padded += '=';
try {
const decoded = atob(padded);
const bytes = new Uint8Array(decoded.length);
for (let i = 0; i < decoded.length; i++) bytes[i] = decoded.charCodeAt(i);
return bytes;
} catch (e) { return null; }
};
const tryBase64Decode = (str) => {
const bytes = tryBase64DecodeBytes(str);
if (!bytes) return null;
let decoded = '';
for (let i = 0; i < bytes.length; i++) decoded += String.fromCharCode(bytes[i]);
return decoded;
};
const findJWTInString = (str) => {
const re = /[A-Za-z0-9_-]+\.[A-Za-z0-9_-]+\.[A-Za-z0-9_-]+/g;
let match;
while ((match = re.exec(str)) !== null) {
if (isValidJWT(match[0])) return match[0];
}
return null;
};
const escapeHtml = (value) => value.replace(/[&<>"']/g, (ch) => ({
'&': '&', '<': '<', '>': '>', '"': '"', "'": '''
})[ch]);
const bytesToUtf8 = (bytes) => {
try { return new TextDecoder('utf-8', { fatal: true }).decode(bytes); } catch (e) { return null; }
};
const readUint32BE = (bytes, offset) => (
((bytes[offset] << 24) >>> 0) + (bytes[offset + 1] << 16) + (bytes[offset + 2] << 8) + bytes[offset + 3]
) >>> 0;
const CRC32_TABLE = (() => {
const table = new Uint32Array(256);
for (let n = 0; n < table.length; n++) {
let c = n;
for (let k = 0; k < 8; k++) c = (c & 1) ? (0xedb88320 ^ (c >>> 1)) : (c >>> 1);
table[n] = c >>> 0;
}
return table;
})();
const crc32 = (bytes) => {
let crc = 0xffffffff;
for (let i = 0; i < bytes.length; i++) crc = CRC32_TABLE[(crc ^ bytes[i]) & 0xff] ^ (crc >>> 8);
return (crc ^ 0xffffffff) >>> 0;
};
const unwrapElasticChecksum = (bytes) => {
if (bytes.length < 8) return null;
const separatorOffset = bytes.length - 8;
if (
bytes[separatorOffset] !== 0 || bytes[separatorOffset + 1] !== 0 ||
bytes[separatorOffset + 2] !== 0 || bytes[separatorOffset + 3] !== 0
) {
return null;
}
const payload = bytes.subarray(0, separatorOffset);
return crc32(payload) === readUint32BE(bytes, bytes.length - 4) ? payload : null;
};
const readLz4Length = (bytes, state, initialLength) => {
let length = initialLength;
if (length !== 15) return length;
let next;
do {
if (state.offset >= bytes.length) throw new Error('Invalid LZ4 length');
next = bytes[state.offset++];
length += next;
} while (next === 255);
return length;
};
const decompressLz4BlockWithLength = (bytes) => {
if (bytes.length < 4) return null;
const outputLength = readUint32BE(bytes, 0);
if (outputLength === 0 || outputLength > 1024 * 1024) return null;
const output = new Uint8Array(outputLength);
const state = { offset: 4 };
let outputOffset = 0;
try {
while (state.offset < bytes.length) {
const token = bytes[state.offset++];
const literalLength = readLz4Length(bytes, state, token >> 4);
if (state.offset + literalLength > bytes.length || outputOffset + literalLength > outputLength) return null;
output.set(bytes.subarray(state.offset, state.offset + literalLength), outputOffset);
state.offset += literalLength;
outputOffset += literalLength;
if (state.offset >= bytes.length) break;
if (state.offset + 2 > bytes.length) return null;
const matchOffset = bytes[state.offset] | (bytes[state.offset + 1] << 8);
state.offset += 2;
if (matchOffset === 0 || matchOffset > outputOffset) return null;
const matchLength = readLz4Length(bytes, state, token & 0x0f) + 4;
if (outputOffset + matchLength > outputLength) return null;
for (let i = 0; i < matchLength; i++) {
output[outputOffset + i] = output[outputOffset - matchOffset + i];
}
outputOffset += matchLength;
}
} catch (e) {
return null;
}
return outputOffset === outputLength ? output : null;
};
const decodeElasticWrappedJWT = (encoded) => {
const bytes = tryBase64DecodeBytes(encoded);
if (!bytes) return null;
const checksumPayload = unwrapElasticChecksum(bytes);
if (!checksumPayload) return null;
const decompressed = decompressLz4BlockWithLength(checksumPayload);
const decodedPayload = decompressed ? bytesToUtf8(decompressed) : bytesToUtf8(checksumPayload);
if (!decodedPayload) return null;
const jwt = findJWTInString(decodedPayload);
if (!jwt) return null;
const transforms = ['Base64-decoded', 'Verified Elastic checksum'];
if (decompressed) transforms.push('LZ4-decompressed');
transforms.push('Extracted JWT from Elastic token');
return { jwt, transforms };
};
// Unwraps Bearer prefixes, opaque session tokens, and base64-wrapped envelopes
// around a real JWT, so users can paste whatever their HTTP tooling shows.
const extractJWT = (input) => {
input = input.trim();
if (!input) return null;
const bearerMatch = input.match(/^Bearer\s+(.+)$/i);
if (bearerMatch) {
const result = extractJWT(bearerMatch[1]);
if (result) return { jwt: result.jwt, transforms: ['Stripped <code>Bearer</code> prefix', ...result.transforms] };
}
if (isValidJWT(input)) return { jwt: input, transforms: [] };
const segments = input.split('_');
for (let i = 1; i < segments.length && i <= 5; i++) {
const remainder = segments.slice(i).join('_');
const prefix = segments.slice(0, i).join('_') + '_';
const prefixLabel = `<code>${escapeHtml(prefix)}</code>`;
if (isValidJWT(remainder)) {
return { jwt: remainder, transforms: [`Stripped prefix ${prefixLabel}`] };
}
const elasticWrapped = decodeElasticWrappedJWT(remainder);
if (elasticWrapped) {
return { jwt: elasticWrapped.jwt, transforms: [`Stripped prefix ${prefixLabel}`, ...elasticWrapped.transforms] };
}
const decoded = tryBase64Decode(remainder);
if (decoded) {
const jwt = findJWTInString(decoded);
if (jwt) {
return { jwt, transforms: [`Stripped prefix ${prefixLabel}`, 'Base64-decoded', 'Extracted JWT from decoded payload'] };
}
}
}
const decoded = tryBase64Decode(input);
if (decoded) {
const jwt = findJWTInString(decoded);
if (jwt) {
return { jwt, transforms: ['Base64-decoded', 'Extracted JWT from decoded payload'] };
}
}
return null;
};
const showTransformInfo = (transforms) => {
if (transforms && transforms.length > 0) {
transformInfo.innerHTML = '<strong>Unwrapped token:</strong> ' + transforms.join(' \u2192 ');
transformInfo.style.display = '';
} else {
transformInfo.style.display = 'none';
transformInfo.innerHTML = '';
}
};
const showParseError = (message) => {
if (message) {
parseError.textContent = message;
parseError.style.display = '';
} else {
parseError.style.display = 'none';
parseError.textContent = '';
}
};
// Rewrites the encoded pane with the three colored segment spans. Used by
// every code path that produces a clean token without a live caret to
// preserve - `loadDefaults` / `updateEncoded` (signing), `extractJWT`
// unwrap, and the paste/drop handlers. Typing into the pane intentionally
// does NOT call this, because rewriting `innerHTML` on every keystroke
// would reset the caret to position 0.
const renderColoredToken = (jwt) => {
const [h, p, s] = jwt.split('.');
const parts = [
['token-part-header', h], ['token-dot', '.'],
['token-part-payload', p], ['token-dot', '.'],
['token-part-signature', s],
];
encodedOutput.replaceChildren(...parts.map(([className, text]) => {
const span = document.createElement('span');
span.className = className;
span.textContent = text ?? '';
return span;
}));
};
const clearDecodedPanels = () => {
const headerEl = document.getElementById('decoded-header');
const payloadEl = document.getElementById('decoded-payload');
if (headerEl) headerEl.value = '';
if (payloadEl) payloadEl.value = '';
populateTable('header-claims-table', null);
populateTable('payload-claims-table', null);
signatureStatus.textContent = '';
signatureStatus.className = '';
};
const updateSignatureStatusUI = (isValid) => {
signatureStatus.textContent = isValid ? 'Signature Verified' : 'Invalid Signature';
signatureStatus.className = isValid ? 'sig-valid' : 'sig-invalid';
};
const updateDecodedFromToken = () => {
const rawInput = encodedOutput.innerText;
showParseError(null);
const result = extractJWT(rawInput);
if (!result) {
showTransformInfo(null);
if (rawInput.trim()) {
clearDecodedPanels();
showParseError('Could not parse as JWT. Expected format: header.payload.signature (base64url-encoded, dot-separated).');
}
return;
}
const { jwt, transforms } = result;
showTransformInfo(transforms);
if (transforms.length > 0) {
renderColoredToken(jwt);
}
const parts = jwt.split('.');
try {
const headerJson = JSON.parse(base64UrlDecode(parts[0]));
document.getElementById('decoded-header').value = JSON.stringify(headerJson, null, 2);
populateTable('header-claims-table', headerJson);
} catch (e) {
document.getElementById('decoded-header').value = base64UrlDecode(parts[0]) || '';
populateTable('header-claims-table', null);
}
try {
const payloadJson = JSON.parse(base64UrlDecode(parts[1]));
document.getElementById('decoded-payload').value = JSON.stringify(payloadJson, null, 2);
populateTable('payload-claims-table', payloadJson);
} catch (e) {
document.getElementById('decoded-payload').value = base64UrlDecode(parts[1]) || '';
populateTable('payload-claims-table', null);
}
verifyToken();
};
const updateEncoded = async () => {
showTransformInfo(null);
showParseError(null);
let header, payload;
try {
header = JSON.parse(document.getElementById('decoded-header').value);
payload = JSON.parse(document.getElementById('decoded-payload').value);
} catch {
encodedOutput.textContent = 'Invalid JSON';
updateSignatureStatusUI(false);
return;
}
if (header.alg !== algorithmSelect.value) {
header.alg = algorithmSelect.value;
document.getElementById('decoded-header').value = JSON.stringify(header, null, 2);
}
try {
const secretKey = new TextEncoder().encode(secretInput.value);
const jwt = await new jose.SignJWT(payload).setProtectedHeader(header).sign(secretKey);
renderColoredToken(jwt);
updateSignatureStatusUI(true);
} catch (err) {
encodedOutput.textContent = `Error: ${err.message}`;
updateSignatureStatusUI(false);
}
};
const verifyToken = async () => {
const token = encodedOutput.innerText;
const secret = secretInput.value;
if (!token || !secret || token.split('.').length !== 3) {
updateSignatureStatusUI(false); return;
}
try {
const secretKey = new TextEncoder().encode(secret);
await jose.jwtVerify(token, secretKey, { algorithms: [algorithmSelect.value] });
updateSignatureStatusUI(true);
} catch (err) { updateSignatureStatusUI(false); }
};
const populateTable = (tableBodyId, data) => {
const tbody = document.getElementById(tableBodyId);
if (!tbody) return;
tbody.innerHTML = '';
if (!data || typeof data !== 'object') return;
for (const key in data) {
const row = tbody.insertRow();
const cellKey = row.insertCell();
const cellValue = row.insertCell();
let keyHtml = `<div>${key}</div>`;
if (JWT_CLAIMS[key]) {
keyHtml += `<span class="claims-desc">${JWT_CLAIMS[key]}</span>`;
}
cellKey.innerHTML = keyHtml;
const value = data[key];
if ((key === 'iat' || key === 'exp' || key === 'nbf') && typeof value === 'number') {
cellValue.textContent = `${value} (${new Date(value * 1000).toUTCString()})`;
} else {
cellValue.textContent = JSON.stringify(value);
}
}
};
// Renders the JSON editor + claim table inside a card body. Both panes are
// always present in the DOM; the global view-tabs at the panel-bar toggles
// which one is active across all cards at once.
const renderCardBody = (contentContainerId, idPrefix) => {
const contentDiv = document.getElementById(contentContainerId);
contentDiv.innerHTML = `
<div data-tab-content="json" class="tab-content active">
<textarea id="decoded-${idPrefix}" spellcheck="false" class="json-editor"></textarea>
</div>
<div data-tab-content="table" class="tab-content">
<table class="claims-table">
<tbody id="${idPrefix}-claims-table"></tbody>
</table>
</div>`;
document.getElementById(`decoded-${idPrefix}`).addEventListener('input', () => {
try {
const jsonData = JSON.parse(document.getElementById(`decoded-${idPrefix}`).value);
populateTable(`${idPrefix}-claims-table`, jsonData);
updateEncoded();
} catch {
/* invalid JSON - wait for the user to finish typing */
}
});
};
renderCardBody('header-tab-content', 'header');
renderCardBody('payload-tab-content', 'payload');
// Global JSON ↔ Table switcher - applies to every card body in the right
// pane simultaneously, so users don't have to keep both per-card tabs in
// sync manually.
const viewTabsEl = document.getElementById('view-tabs');
viewTabsEl.addEventListener('click', (e) => {
if (!e.target.classList.contains('view-tab')) return;
for (const btn of viewTabsEl.querySelectorAll('.view-tab')) {
btn.classList.remove('active');
btn.setAttribute('aria-selected', 'false');
}
e.target.classList.add('active');
e.target.setAttribute('aria-selected', 'true');
const view = e.target.dataset.view;
for (const content of document.querySelectorAll('[data-tab-content]')) {
content.classList.toggle('active', content.dataset.tabContent === view);
}
});
algorithmSelect.addEventListener('change', updateEncoded);
secretInput.addEventListener('input', updateEncoded);
encodedOutput.addEventListener('input', updateDecodedFromToken);
// The encoded pane is a contenteditable div, so the browser's default
// paste/drop inserts the source's rich HTML (with its own inline styles
// like `white-space: nowrap` or `<pre>` wrappers) which overrides the
// pane's `white-space: pre-wrap; word-break: break-all` and produces a
// single overflowing line. Force plain text on every insertion path so
// the layout stays wrapped regardless of where the token came from.
const insertPlainText = (text) => {
const selection = window.getSelection();
if (!selection || selection.rangeCount === 0) {
encodedOutput.textContent = text;
} else {
const range = selection.getRangeAt(0);
if (!encodedOutput.contains(range.commonAncestorContainer)) {
encodedOutput.textContent = text;
} else {
range.deleteContents();
range.insertNode(document.createTextNode(text));
range.collapse(false);
selection.removeAllRanges();
selection.addRange(range);
}
}
encodedOutput.dispatchEvent(new Event('input', { bubbles: true }));
};
// After a paste/drop produces a clean bare JWT, colorize the three
// segments. `updateDecodedFromToken` (run via the dispatched input event)
// intentionally only colorizes when an envelope was unwrapped, to avoid
// resetting the caret on every keystroke during typing. Paste/drop is the
// one moment where there is no live caret to preserve, so we can safely
// recolor here.