compresion

library1.7.11jsnpmunverified

Node.js compression middleware for Express/Connect that provides gzip and deflate encoding. Current stable version is 1.8.1 (August 2024). Maintained by the Express.js team with monthly releases. Handles content negotiation, cache-control respecting, and configurable zlib options. Key differentiator is seamless integration with Express routing, supporting threshold, filter, and level settings. Not a standalone compressor; must be used with Node.js HTTP server or framework. Legacy support for Node >=0.8.0.

web-framework http-networking

npm install compresion

github ↗package ↗

INSTALL

IMPORT

SIG · COMPRESION

compresion

web-frameworkjavascriptv1.7.11

Install

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Import

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Disk

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Pass rate

0/ 6

Env Coverage0 / 6

glibc

18–22

musl

18–22

Install & Compatibility

Where this runs

tested against v? · npm install

Install × environment matrix

Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux

musl

node 18–226 runs

build_error

glibc

node 18–226 runs

build_error

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

compression

✓ import compression from 'compression'

✗ const compression = require('compression')

ESM is supported in v1.8+ with conditional exports; default import works. For CommonJS, require('compression') is still valid.

CompressionOptions

✓ import type { CompressionOptions } from 'compression'

TypeScript users can import the options interface for type safety.

Creates an Express server with compression middleware applied globally to compress responses.

import compression from 'compression'; import express from 'express'; const app = express(); // apply compression middleware app.use(compression()); // normal route app.get('/data', (req, res) => { res.json({ message: 'This response will be compressed' }); }); app.listen(3000, () => console.log('Server listening on port 3000'));

Debug

Known issues

breakingIn v1.7.0, changed from using raw Buffer to safe-buffer for improved Buffer API compatibility. This may affect custom compression filter functions that rely on Buffer constructors.

fix

Update any code that explicitly uses Buffer to use safe-buffer's Buffer if needed.

affects: >=1.7.0

deprecatedIn v1.8.0, the `_header` property is deprecated in favor of `headersSent`. Code that directly checks `res._header` may break in future Node.js versions.

fix

Replace `res._header` with `res.headersSent` in custom filter or hook functions.

affects: >=1.8.0

gotchaDo NOT call `res.end()` or pipe the response before compression middleware runs. The middleware must intercept the response stream; otherwise compression will not be applied and may cause errors.

fix

Ensure `compression()` is inserted in middleware stack before any route handlers that write to the response.

affects: *

gotchaCompression is automatically skipped if the response has `Cache-Control: no-transform`. This is a feature to respect CDN and proxy transformations, but can be surprising if you expect compression overrides.

fix

Remove `no-transform` from Cache-Control header if you want forced compression.

affects: *

breakingIn v1.6.0, the default `level` changed from 6 to -1 (zlib default). With newer Node versions, the underlying zlib default may vary, affecting compression ratio consistency.

fix

Explicitly set `level` option if you need a specific compression level.

affects: >=1.6.0

Errors

Common errors & fixes

TypeError: compression is not a function

Incorrect import: using `require('compression')` in an ESM environment or importing as default without default import.

fix

Use `import compression from 'compression'` or use `const compression = require('compression').default` if using CommonJS in ESM context.

ERR_INVALID_ARG_TYPE: The "level" argument must be of type number. Received undefined

Passing options to `compression()` where `level` is not a number (e.g., string).

fix

Ensure `level` option is a number between -1 and 9.

Cannot set property 'writeHead' of undefined

Compression middleware was applied after response has already been written or ended (e.g., placed after route handlers).

fix

Move `app.use(compression())` before all route handlers.

Upgrade

Version history

1.7.11latest on npm

Audit

Dependencies

acceptsrequiredcontent negotiation for compression encoding

bytesrequiredparse content-length and threshold values

compressiblerequiredcheck if response content type is compressible

debugrequireddebugging and logging

on-headersrequiredhook into response headers to apply compression before write

safe-bufferrequiredpolyfill for Buffer API (used in older Node versions)

varyrequiredset Vary header for content negotiation

Agent activity

15 hits · last 30 days

node

OpenAI (training)

Resources

githubhttps://github.com/expressjs/compression ↗

packagehttps://www.npmjs.com/package/compresion ↗