node:zlib

node:zlib follows Node’s zlib, including Brotli, Zstandard, and crc32. For Web Streams, use Compression Streams.

Example

// zlib.mjs
import { brotliCompressSync, crc32, gunzipSync, gzipSync, zstdCompressSync, zstdDecompressSync } from "node:zlib";

const text = "elide ".repeat(100);
const gz = gzipSync(text);
console.log(text.length, "->", gz.length, gunzipSync(gz).toString() === text);
console.log(zstdDecompressSync(zstdCompressSync(text)).toString().length);
console.log(brotliCompressSync(text).length < text.length, crc32("elide"));

utf-8 · js · Lines: 8

elide run zlib.mjs prints:

text

600 -> 35 true
600
true 2639236160

utf-8 · text · Lines: 3

Differences from Node

Constants live only on zlib.constants; the top-level Z_*, ZSTD_* and mode aliases such as zlib.Z_OK are undefined.
node:zlib/iter is an Elide extension. It exports compress* and decompress* factories (Gzip, Deflate, DeflateRaw, Brotli, Zstd, each with a Sync form) and the aliases gzip, gunzip, deflate, inflate, deflateRaw, and inflateRaw. Each factory’s .transform(asyncIterable) yields batches of byte chunks, as in for await (const batch of gzip().transform(input)).

Reference

Status: Partial · Not measured · since 1.1.0

Exports

Export	Kind	Status	Notes
`deflateSync()`	function	Full	Compress data using the deflate algorithm (RFC 1951 wrapped in zlib format RFC 1950)
`inflateSync()`	function	Full	Decompress data that was compressed with deflate (zlib format)
`deflateRawSync()`	function	Full	Compress data using the deflate algorithm in raw mode (no zlib header, RFC 1951)
`inflateRawSync()`	function	Full	Decompress raw deflate data (no zlib header)
`gzipSync()`	function	Full	Compress data using gzip (RFC 1952)
`gunzipSync()`	function	Full	Decompress gzip data (RFC 1952)
`brotliCompressSync()`	function	Full	Compress data using the Brotli algorithm (RFC 7932)
`brotliDecompressSync()`	function	Full	Decompress Brotli-compressed data (RFC 7932)
`unzipSync()`	function	Full	Decompress data with automatic format detection (gzip or deflate)
`constants`	property	Full	The `constants` object exposes zlib, Brotli, and Zstd numeric constants
top-level constants	constant	Partial	`Z_NO_COMPRESSION`, `Z_BEST_SPEED`, `Z_BEST_COMPRESSION`, `Z_DEFAULT_COMPRESSION`, `Z_FILTERED`, `Z_HUFFMAN_ONLY` and 73 more

Not implemented

107 top-level constants such as DEFLATE.