A mempool monitor in a browser tab. The shape everyone knows from mempool.space, the projected blocks on the left of the chain tip and the mined ones on the right, but every transaction on the page was validated by the tab's own node, and the next block is the one this tab would build.
Live: https://bitcoin-blake.github.io/bight/
One page over blaketestnode's browser node, through the same loader Reef uses (browser/tabnode.js, pinned by commit): the tab fetches the fork-point UTXO snapshot of txbt4 (the BLAKE2b testnet4), checks its hashes, validates every block since the fork and follows the chain tip. Then it keeps its own mempool: transactions arrive as kind 23404 events (a node publishing its mempool, one transaction per event), as kind 23503 events (sends from sidestr wallets), and from the mirror's mempool file on start; each is checked against the tab's own UTXO set (inputs unspent and mature, values, scripts, a fee floor) before it counts, and the tab never relays one onward.
On the page:
- Blocks. The next blocks packed by fee rate from the tab's mempool; the first is also built in full by the node worker (coinbase, witness commitment, header) and checked against every block rule it knows: when that build is on the current tip and passes, the tile carries "✓ built" and the panel the node's own figures. To the right, the last blocks the tab validated, with the size-weighted median rate of the transactions it knew ("of N known") and how many it had seen in its mempool first. Every tile is a button; its detail opens beside the row.
- Mempool. Count, size, fees waiting, the size-weighted median rate, the fee bands (with a table for screen readers), and the newest 300 transactions; a txid opens its detail in the page, the ↗ beside it opens mempool.guide (another site, not checked by this tab).
- Where it comes from. The relays asked (the node does not report which answer), how many transactions were heard, accepted, refused and dropped (mined or evicted), what the mirror's file gave on start, when the publisher last reported and when it last sent a transaction, and the last refusals with the reason.
- Over time. Transactions and vB through the session.
- Search a txid or its first 8 or more characters, a block hash or a block height: the mempool (the node is asked for a transaction it sent only compactly), the blocks the tab holds ("Found in block N"), then what it saw; a miss says which blocks were searched.
A UTXO node keeps no history: fees of transactions the tab never had are shown as unknown rather than guessed, and a search beyond the last blocks says so.
Bight and Reef publish under the same origin, so they share one copy of the snapshot in the browser's storage. Settings (⚙) hold the snapshot and blocks URLs, the swarm fetch (WebTorrent, the mirror as webseed), seeding, and Wipe.
The first visit downloads the chain's state at block 150,307 (870 MB) and needs about 1.2 GB of the browser's storage for this site; Bight asks first (one answer for Bight and Reef). The files are shared with Reef, Winch and Hitch on the same site, and one tab of the four runs the node at a time: a second tab says it is idle and takes over when the other closes. A private window cannot run the node. Settings → Wipe removes the node's files for all four (the key in Reef is not touched).
A link may propose another snapshot or block source (?snapshot=, ?blocks=): it is shown in a notice and used only for the visit you agree to, never stored.
- Signed chain tip. The node checks the block source against a NIP-333 signed tip. The pill reads "signed" when they agree at the node's height, warns when the source runs above the tip (those blocks are marked "not signed yet"), and turns red when they disagree.
- The whole mempool. The node (since 5550637) sends every transaction compactly (txid, size, fee, when, fed) and the first 1,000 by fee rate whole; the bands, median, projected blocks and search cover all of it. From an older node sending only 1,000, the page says "the top 1,000 of N".
- The next block. Projected blocks are packed the way the node packs its own (by fee rate, skipping what does not fit). The node does not send its template's txids, so the first tile shows the page's packing and the node's figures side by side, "✓ built" only when that build is on the current tip (height and parent) and passes every rule it checks; otherwise it says which rules fail. With an empty mempool the next block is the coinbase alone.
- Seen first. Counted only for a block whose whole interval the tab listened for (the block before it also arrived after the mempool was followed); otherwise "not listening then".
- Sources. A snapshot or block source that is not the default (Bight's, Reef's, or a link's accepted for the visit) is said in a lasting notice with "Back to the default".
- A block's fees. A UTXO node never sees the fees of transactions it did not hold, so a block's fees are what its coinbase claimed (its value, sent by the node since c3f6a46, less the subsidy): a miner may claim less than it collected.
- Times. A block watched arriving on its own is aged, and its "seen … before the block" measured, from when it reached the tab; one from a catch-up (at start, after sleep) by its header, and the detail says which. The projected blocks' ETAs use the spacing of the last blocks' headers (20 minutes until there are enough).
| Service | What it provides | What the page says when it is down |
|---|---|---|
| The block mirror (melvin.me) | the snapshot, the block file and index, context headers, the mempool seed | a node error in words; after sync "no answer from the block source since …" and "no new block for N minutes"; the seed "not loaded: …" |
| The NIP-333 tip publisher | the signed chain tip | "no signed chain tip reached this browser" |
| The estate's mempool feed (kind 23404) | a node's own mempool | its heartbeat is the mirror's mempool file, rewritten every pass: "has not reported since …" after 10 minutes (a quiet chain is not a dead feed) |
| Nostr relays | the feed and wallet sends | the relay count followed, and the counts heard |
| cdn.jsdelivr.net | the node's code, pinned by commit and hash-checked by the loader | "could not load its code"; "the node has said nothing for a minute"; "not the pinned code" |
| The node's worker | the node itself | "not answering" (amber) while it is silent for two minutes, cleared when it answers |
| GitHub Pages | the page | the browser's own error |
The security policy's connect-src allows any https: and wss: address on purpose: the snapshot and block sources are the person's to choose in Settings (or a link's, for a visit they agree to), and the relays are many. Scripts and workers are held to the pinned commits (script-src, worker-src), so a source can be read from, never run.
npm test runs the page's decisions (test/lib-test.mjs) and the registry app (test/app-test.mjs). node test/smoke.mjs (needs npm i --no-save playwright-core) loads the page in headless Chromium with a fake node (test/fake/tabnode.js).
The page is built for keyboard and screen reader use: tiles are buttons with full names, the detail takes the focus and gives it back, notices are announced only when new or more serious, the fee colours keep white text at 4.5:1 or better, and forced colours and reduced motion are honoured.
GitHub Pages serves main as it is. Bump the version in bight.js (VERSION), version.json, and bight.js?v= and theme.js?v= in index.html together, and push. A new node pin goes into bight.js and the policy in index.html, and into Reef, Winch and Hitch in the same sitting: the four share the node's files and its lock.
A bight is the slack curve of a line before it is made fast, which is what a mempool is. Reef is a knot; Bight is the rope beside it.
AGPL-3.0-or-later.