MiniExcel for Rust

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Fast XLSX and CSV processing with bounded-memory streaming.

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Part of the MiniExcel project family, with the .NET library as its compatibility reference.

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Open the Browser Lab to inspect or generate XLSX files locally. Workbook data stays in the browser.

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Introduction

MiniExcel for Rust is an XLSX and CSV reader/writer with bounded-memory streaming, Serde support, analytics, and RAG exports.

Install

cargo add miniexcel

Requires Rust 1.85.0 or later.

.NET Package

The repository also builds the prerelease MiniExcel.Rust NuGet package. It depends on MiniExcel v1 1.46.0, reuses its configuration and mapping types, and routes calls made through MiniExcelRust to the Rust native library.

dotnet add package MiniExcel.Rust --version 0.1.0-preview.2

using MiniExcelLibs;
using MiniExcelLibs.OpenXml;

var rows = MiniExcelRust.Query(
    "book.xlsx",
    useHeaderRow: true,
    configuration: new OpenXmlConfiguration { IgnoreEmptyRows = true });

Use MiniExcel.Query for the original managed implementation and MiniExcelRust.Query for the Rust-backed implementation. Build and consume a local package with ./scripts/dotnet/Test-Package.ps1 -Rid win-x64.

Quick Start

use miniexcel::MiniExcel;

for row in MiniExcel::query("book.xlsx")? {
    println!("{:?}", row?["A"]);
}

use miniexcel::{CellValue, DynamicRow, MiniExcel};

let mut row = DynamicRow::new();
row.insert("Name".into(), CellValue::String("MiniExcel".into()));
MiniExcel::save_as("book.xlsx", &[row])?;

Capabilities

• Bounded-memory dynamic, typed, structured, table, and CSV queries.
• Path, byte-array, and borrowed reader/writer APIs.
• Serde reading and writing; date/time helpers and exact-cell mapping.
• Multi-sheet creation, formatting options, and worksheet visibility.
• Atomic worksheet insert/replace, rename, reorder, copy, and visibility changes.
• Template rendering, conditional/group blocks, and marker-driven cell merging.
• Streaming grouped analytics with explicit limits.
• Source-addressed JSONL and Markdown exports for LLM/RAG workflows.
• Optional runtime-neutral async streams; ZIP/XML/filesystem work remains blocking.

Key Semantics

• Path queries stream worksheet XML and do not retain all rows.
• The default worksheet is the first worksheet, not the active tab.
• Formula reads return cached values; structured reads also expose formula text and formats. MiniExcel does not calculate formulas.
• Save creates a new workbook and refuses existing paths by default. Insert APIs modify .xlsx files atomically after validation.
• Large shared-string tables may spill to indexed temporary files; byte/WASM queries keep them in memory.
• Not supported: .xls, .xlsb, .ods, macros, image authoring, formula calculation, or a general style system.

See the compatibility matrix, analytics and RAG contract, and Insert migration guide.

Rust And .NET Benchmark

Latest NuGet Results

The latest Windows x64 run compared public MiniExcel 1.46.0, the MiniExcel.Rust 0.1.0-preview.2 .NET wrapper, and native MiniExcel Rust 0.4.0 over a declared-dimension workbook containing 100,000 rows x 10 columns. Five fresh processes ran per runtime and scenario; every row, column, and normalized value matched before timing.

Scenario	Runtime	Median elapsed	Rows/s	First row	Managed allocation	Peak working set
Cold	MiniExcel	2,145.90 ms	46,600	38.77 ms	1,167.07 MB	51.26 MB
Cold	MiniExcel.Rust (.NET)	1,047.67 ms	95,450	12.05 ms	107.04 MB	44.59 MB
Cold	MiniExcel.Rust	855.09 ms	116,947	0.42 ms	n/a	3.70 MB
Steady	MiniExcel	4,341.55 ms	69,100	3.95 ms	3,500.58 MB	54.74 MB
Steady	MiniExcel.Rust (.NET)	2,972.94 ms	100,910	5.50 ms	321.09 MB	48.08 MB
Steady	MiniExcel.Rust	2,143.31 ms	139,970	0.41 ms	n/a	3.79 MB

For full Query, preview.2 is 2.05x faster in Cold and 1.46x faster in Steady than MiniExcel v1, with 90.8% less managed allocation in both scenarios.

Results are machine-specific. Run pwsh ./scripts/compare-nuget-v1-rust.ps1 on representative workbooks; see the benchmark methodology.

Place this repository beside .NET MiniExcel, then run:

pwsh ./scripts/compare-dotnet-v1-rust.ps1 -DotNetRepository D:\git\MiniExcel

The report is written to target/benchmarks/dotnet-v1-vs-rust.json. Compare only results produced on the same machine; see the benchmark methodology.