@reearth/compressible

Tells you whether a file's contents (identified by its extension) are worth gzip-compressing — for example before uploading to a CDN or object store with Content-Encoding: gzip.

The extension list (~230 entries) is curated from jshttp/mime-db: already-compressed and large-binary formats are dropped, and 3D Tiles / Cesium quantized-mesh terrain extensions common in geospatial pipelines are added in.

Install

npm install @reearth/compressible

ESM and CJS are both shipped, with type definitions.

Usage

import {
  isCompressible,
  isCompressiblePath,
  extensions,
} from "@reearth/compressible";

isCompressible("js");                // true
isCompressible(".JSON");             // true — leading dot and case are normalized
isCompressible("png");               // false

isCompressiblePath("a/b/c.html");    // true
isCompressiblePath("img.png");       // false
isCompressiblePath("archive.tar.gz") // false — only the last extension is considered

// Raw access to the underlying set if you need it.
extensions.has("wasm");              // true

Behavior

• The extension may be supplied with or without a leading dot.
• Matching is case-insensitive.
• For paths, only the final extension is considered: archive.tar.gz → gz → not compressible.
• An empty input returns false.

Why not just use mime-db's compressible flag?

mime-db ships some compressible: true entries that aren't actually worth gzipping in practice (VM disk images, DXT-compressed textures, PSDs with internal compression). It also misses formats common in 3D / geospatial pipelines (3D Tiles .b3dm / .i3dm / .pnts / .cmpt / .subtree, Cesium quantized-mesh .terrain).

This library bakes that curation in once so it doesn't have to be re-implemented in every uploader / CDN tool.

Provenance

Releases are published from GitHub Actions with npm provenance, so you can verify which commit and workflow run produced each tarball:

npm view @reearth/compressible

License

MIT — see the repository for details.

Also available for Go.