@gorules/into-md

Converts DOCX, PPTX, XLSX, XLS (Excel 97–2003), ODS, ODT, ODP, RTF and PDF to Markdown in the browser or Node.js: headings, bold/italic, lists, tables, hyperlinks and slide speaker notes.

import { convert, createConverter } from '@gorules/into-md';

const { format, markdown } = await convert(await file.arrayBuffer());

const converter = createConverter({ workers: 1, timeoutMs: 30_000 });
await converter.convert(bytes, { maxMarkdownBytes: 1024 * 1024 });
await converter.close();

Nothing is loaded at import time: the first convert starts a Web Worker (browser) or worker thread (Node.js), which fetches and compiles the WebAssembly module, so the page or event loop never blocks. Each conversion gets a fresh WebAssembly instance (memory capped at 512 MB), so a crash in one document never affects the next, and a conversion that exceeds timeoutMs has its worker terminated. Failures throw IntoMdError with code set to unsupported, encrypted, too-large, malformed, timeout or unavailable (module could not be loaded).

The package ships a single module, into_md.wasm (about 620 KB, 225 KB brotli), fetched and compiled by the worker on the first conversion.

Bundlers that understand new Worker(new URL('./worker.js', import.meta.url)) and new URL('./file.wasm', import.meta.url) (Vite, webpack 5, Rollup, esbuild with plugins) pick up the worker and the module automatically; no configuration is needed. RTF legacy code pages (Cyrillic, Shift-JIS, …) are decoded with the platform TextDecoder.

Limits (all optional, defaults shown):

Option	Default
maxInputBytes	25 MB
maxUncompressedBytes	20 MB, measured by inflating every zip entry before parsing
maxZipEntries	2000
maxXmlElements	500,000
maxTableCells	200,000
maxMarkdownBytes	2 MB

Development

pnpm install
pnpm build         # size-optimized into_md.wasm (needs the nightly pinned in scripts/build.mjs, with rust-src)
pnpm test          # cargo tests + node tests against the built wasm
pnpm notices       # regenerate THIRD_PARTY_LICENSES.md after dependency changes
pnpm fixtures      # regenerate test/fixtures (cocoa.rtf comes from macOS textutil and is kept as is)
pnpm corpus        # download the pinned public corpus (Apache POI, python-docx, python-pptx, LibreOffice, pdf.js) into test/corpus
pnpm compare       # compare against officeparser on the corpus, writes test/corpus/report.json

Releasing

Releases are managed by release-please from Conventional Commits on main (feat: bumps the minor version before 1.0, fix: the patch version). It keeps a release PR open that bumps package.json, crates/into-md/Cargo.toml, Cargo.lock and CHANGELOG.md; merging it tags the release and the Release workflow validates, builds the wasm and runs pnpm publish with provenance. The workflow needs the PAT and NPM_TOKEN secrets. prepack refuses to pack a stale or missing into_md.wasm, missing notices, or mismatched versions.

The Rust workspace lives in crates/:

Crate	Purpose
crates/into-md	the converter compiled to into_md.wasm; the pdf feature (on by default) adds PDF support
crates/pdf	into-md-pdf, a size-reduced fork of pdf-extract 0.12.1 (see its README for what changed)
crates/utf16	stands in for encoding_rs (UTF-16 only), which is all lopdf and the PDF fork need
crates/saslprep	stands in for stringprep; PDFs are only opened with the empty password

The release build uses a pinned nightly with -Z build-std and panic=immediate-abort, which removes panic formatting from the binary. Legacy code pages (RTF, old spreadsheets) are decoded by the host's TextDecoder; native builds fall back to Windows-1252.