Gzip Middleware for Go


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Gzip Middleware for Go

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An out-of-the-box, also customizable gzip middleware for Gin and net/http.

Golang Gzip Middleware


Use DefaultHandler() to create a ready-to-go gzip middleware.


import github.com/nanmu42/gzip

func main() {
	g := gin.Default()

    // use default settings

	g.GET("/", func(c *gin.Context) {
		c.JSON(http.StatusOK, map[string]interface{}{
			"code": 0,
			"msg":  "hello",
			"data": fmt.Sprintf("l%sng!", strings.Repeat("o", 1000)),

	log.Println(g.Run(fmt.Sprintf(":%d", 3000)))


import github.com/nanmu42/gzip

func main() {
	mux := http.NewServeMux()
	mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		writeString(w, fmt.Sprintf("This content is compressed: l%sng!", strings.Repeat("o", 1000)))

    // wrap http.Handler using default settings
	log.Println(http.ListenAndServe(fmt.Sprintf(":%d", 3001), gzip.DefaultHandler().WrapHandler(mux)))

func writeString(w http.ResponseWriter, payload string) {
	w.Header().Set("Content-Type", "text/plain; charset=utf8")
	_, _ = io.WriteString(w, payload+"\n")

Customize Handler

Handler can be customized using NewHandler and Config:

import github.com/nanmu42/gzip

handler := gzip.NewHandler(gzip.Config{
    // gzip compression level to use
	CompressionLevel: 6, 
    // minimum content length to trigger gzip, the unit is in byte.
	MinContentLength: 1024,
    // RequestFilter decide whether or not to compress response judging by request.
    // Filters are applied in the sequence here.
	RequestFilter: []RequestFilter{
    // ResponseHeaderFilter decide whether or not to compress response
    // judging by response header
	ResponseHeaderFilter: []ResponseHeaderFilter{

RequestFilter and ResponseHeaderFilter are interfaces. You may define one that specially suits your need.


  • When response payload is small, the handler is smart enough to skip compression automatically, which takes neglectable overhead.
  • At the time when the payload is big enough, gzip kicks in and there is a reasonable price.
$ go test -benchmem -bench .
goos: linux
goarch: amd64
pkg: github.com/nanmu42/gzip
BenchmarkSoleGin_SmallPayload-4                          4104684               276 ns/op              64 B/op          2 allocs/op
BenchmarkGinWithDefaultHandler_SmallPayload-4            1683307               707 ns/op              96 B/op          3 allocs/op
BenchmarkSoleGin_BigPayload-4                            4198786               274 ns/op              64 B/op          2 allocs/op
BenchmarkGinWithDefaultHandler_BigPayload-4                44780             27636 ns/op             190 B/op          5 allocs/op
ok      github.com/nanmu42/gzip 6.373s

Note: due to an awkward man-mistake, benchmark of and before v1.0.0 are not accurate.


  • You should always provide a Content-Type in http response's header, though handler guesses by http.DetectContentType()as makeshift;
  • When Content-Length is not available, handler may buffer your writes to decide if its big enough to do a meaningful compression. A high MinContentLength may bring memory overhead, although the handler tries to be smart by reusing buffers and testing if len(data) of the first http.ResponseWriter.Write(data []byte) calling suffices or not.

Status: Stable

All APIs are finalized, and no breaking changes will be made in the 1.x series of releases.


During the development of this work, the author took following works/materials as reference:

This package uses klauspost's compress package to handle gzip compression.

Logo generated at Gopherize.me.


MIT License
Copyright (c) 2019 LI Zhennan

Caddy is licensed under the Apache License
Copyright 2015 Light Code Labs, LLC
  • Compression doesn't work for large responces

    Compression doesn't work for large responces

    Hello. My api gives different response sizes. Where the response is small (13kb) compression works fine and returns 1.78kb. But if the size is large (2.75mb), then the response is returned uncompressed, although the Content-Encoding:gzip header is added. I also see that for large responses, the Transfer-Encoding:chunked header is returned, but no Content-Length is returned. What should be done to compress all responses? Compressed: image

    Not compressed: image

    opened by dmitrydvm 3
  • 赞一个!



    Gin的gzip长期没人维护,新功能只能手动拉代码到本地,搞个排除文件扩展名和路径的配置,配也不是,不配也不是... Echo的gzip就是默认所有文档都开启压缩,自己想配个Skipper,结果搞了半天获取不到header里的值(可能是我太菜...)



    用的有个疑问: 1、gzip.NewHandler(gzip.Config{})似乎必须要传入所有参数,仅传入CompressionLevel会报

    invalid MinContentLength: 0


    opened by hyingreborn 2
  • Switch compression package (3x faster)

    Switch compression package (3x faster)

    Use github.com/klauspost/compress package for compression.

    Benchmarks did not actually compress since the header was carried over between calls.

    Before/after are both with the benchmark fix in place.

    λ benchcmp before.txt after.txt
    benchmark                                          old ns/op     new ns/op     delta
    BenchmarkSoleGin_SmallPayload-12                   279           284           +1.79%
    BenchmarkGinWithDefaultHandler_SmallPayload-12     653           662           +1.38%
    BenchmarkSoleGin_BigPayload-12                     271           284           +4.80%
    BenchmarkGinWithDefaultHandler_BigPayload-12       83649         25616         -69.38%

    I believe the last benchmark is the only one actually to be compressing, correct?

    I didn't go out of my way to clean up the benchmark since the difference is rather obvious.

    The compression ratio is likely a bit less, but among many other changes the default settings have been tweaked to give the most reasonable speed/compression tradeoff.

    opened by klauspost 1
  • Do not change response code after 204

    Do not change response code after 204

    There's a bug in the writerwrapper. If you call WriteHeader with either 204 or 304, shouldCompress would be set to false and then all subsequent calls to Write will result in directly calling the OriginWriter.Write but since the status code is not written to OriginWriter, it will set it to 200. Another side effect of this is that Write will not only set the status code to 200 but it will also write the content of data to Body which would not normally happen if the gzip middleware is not used. Instead, if you set the status code to 204 or 304, any calls to Write will fail with an error. The correct unit test for this would be:

    func Test_writeWrapper_does_not_change_status_code_after_204(t *testing.T) {
    	wrapper, recorder := newWrapper()
    	n, err := wrapper.Write([]byte("something"))
    	assert.Equal(t, 0, n)
    	assert.Error(t, err)
    	assert.Equal(t, http.StatusNoContent, recorder.Code)
    	assert.Equal(t, []byte{}, recorder.Body.Bytes())

    The problem is that recorder actually behaves differently from server.response and won't check for 204, 304 (the actual call that server.response makes is bodyAllowedForStatus(w.status)) so recorder will both manage to record the 204 status code and the body (which won't happen in reality). Yet, I didn't find a way to instantiate the actual server.response and test against it. So, in the unit tests, the body will be written but in actual use cases, an error will be thrown as expected.

    opened by hrist0stoichev 0
  • Add support for serving precompressed static files from ServeFile

    Add support for serving precompressed static files from ServeFile

    Thanks for providing this useful middleware first of all. I'm wondering if the Static files from http.ServeFile method is also supported. Especially,

    It would also be 'nice to have' if the http.ServeFile method would check for the presence of xxx.gz and serve it if present and the accept header includes gzip. This is a trick that nginx does and it greatly accelerates the serving of static css, js etc files because they can be compressed just once during the build process. There's the added benefit too that they are smaller files to read, as well as needing fewer bytes on the wire


    enhancement help wanted 
    opened by suntong 3
  • v1.2.0(Sep 18, 2021)

    v1.2.0 is a bug fix release:

    • fix: Do not change response code after 204 and 304 (#5)

    Thanks to @hstoychev-cb for the wonderful contribution.

    Source code(tar.gz)
    Source code(zip)
  • v1.1.0(Nov 29, 2020)

    • refactor: switch gzip implmentation from official gzip to github.com/klauspost/compress(#3, thanks to @klauspost)
    • vendor: bump dependency version
    • doc: acknoledgement and performance correction
    • refactor: simplify writerWrapper.enoughContentLength()
    Source code(tar.gz)
    Source code(zip)
  • v1.0.0(Apr 26, 2020)

LI Zhennan
To build beautiful things beautifully.
LI Zhennan
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