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Published: Feb 21, 2019 License: Apache-2.0 Imports: 10 Imported by: 1,251


Gzip Handler

This is a tiny Go package which wraps HTTP handlers to transparently gzip the response body, for clients which support it. Although it's usually simpler to leave that to a reverse proxy (like nginx or Varnish), this package is useful when that's undesirable.


go get -u github.com/NYTimes/gziphandler


Call GzipHandler with any handler (an object which implements the http.Handler interface), and it'll return a new handler which gzips the response. For example:

package main

import (

func main() {
	withoutGz := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", "text/plain")
		io.WriteString(w, "Hello, World")

	withGz := gziphandler.GzipHandler(withoutGz)

	http.Handle("/", withGz)
	http.ListenAndServe("", nil)


The docs can be found at godoc.org, as usual.


Apache 2.0.




View Source
const (
	// DefaultQValue is the default qvalue to assign to an encoding if no explicit qvalue is set.
	// This is actually kind of ambiguous in RFC 2616, so hopefully it's correct.
	// The examples seem to indicate that it is.
	DefaultQValue = 1.0

	// DefaultMinSize is the default minimum size until we enable gzip compression.
	// 1500 bytes is the MTU size for the internet since that is the largest size allowed at the network layer.
	// If you take a file that is 1300 bytes and compress it to 800 bytes, it’s still transmitted in that same 1500 byte packet regardless, so you’ve gained nothing.
	// That being the case, you should restrict the gzip compression to files with a size greater than a single packet, 1400 bytes (1.4KB) is a safe value.
	DefaultMinSize = 1400


This section is empty.


func CompressionLevel

func CompressionLevel(level int) option

func ContentTypes

func ContentTypes(types []string) option

ContentTypes specifies a list of content types to compare the Content-Type header to before compressing. If none match, the response will be returned as-is.

Content types are compared in a case-insensitive, whitespace-ignored manner.

A MIME type without any other directive will match a content type that has the same MIME type, regardless of that content type's other directives. I.e., "text/html" will match both "text/html" and "text/html; charset=utf-8".

A MIME type with any other directive will only match a content type that has the same MIME type and other directives. I.e., "text/html; charset=utf-8" will only match "text/html; charset=utf-8".

By default, responses are gzipped regardless of Content-Type.

func GzipHandler

func GzipHandler(h http.Handler) http.Handler

GzipHandler wraps an HTTP handler, to transparently gzip the response body if the client supports it (via the Accept-Encoding header). This will compress at the default compression level.

func GzipHandlerWithOpts

func GzipHandlerWithOpts(opts ...option) (func(http.Handler) http.Handler, error)

func MinSize

func MinSize(size int) option

func MustNewGzipLevelHandler

func MustNewGzipLevelHandler(level int) func(http.Handler) http.Handler

MustNewGzipLevelHandler behaves just like NewGzipLevelHandler except that in an error case it panics rather than returning an error.

func NewGzipLevelAndMinSize

func NewGzipLevelAndMinSize(level, minSize int) (func(http.Handler) http.Handler, error)

NewGzipLevelAndMinSize behave as NewGzipLevelHandler except it let the caller specify the minimum size before compression.

func NewGzipLevelHandler

func NewGzipLevelHandler(level int) (func(http.Handler) http.Handler, error)

NewGzipLevelHandler returns a wrapper function (often known as middleware) which can be used to wrap an HTTP handler to transparently gzip the response body if the client supports it (via the Accept-Encoding header). Responses will be encoded at the given gzip compression level. An error will be returned only if an invalid gzip compression level is given, so if one can ensure the level is valid, the returned error can be safely ignored.


type GzipResponseWriter

type GzipResponseWriter struct {
	// contains filtered or unexported fields

GzipResponseWriter provides an http.ResponseWriter interface, which gzips bytes before writing them to the underlying response. This doesn't close the writers, so don't forget to do that. It can be configured to skip response smaller than minSize.

func (*GzipResponseWriter) Close

func (w *GzipResponseWriter) Close() error

Close will close the gzip.Writer and will put it back in the gzipWriterPool.

func (*GzipResponseWriter) Flush

func (w *GzipResponseWriter) Flush()

Flush flushes the underlying *gzip.Writer and then the underlying http.ResponseWriter if it is an http.Flusher. This makes GzipResponseWriter an http.Flusher.

func (*GzipResponseWriter) Hijack

func (w *GzipResponseWriter) Hijack() (net.Conn, *bufio.ReadWriter, error)

Hijack implements http.Hijacker. If the underlying ResponseWriter is a Hijacker, its Hijack method is returned. Otherwise an error is returned.

func (*GzipResponseWriter) Push

func (w *GzipResponseWriter) Push(target string, opts *http.PushOptions) error

Push initiates an HTTP/2 server push. Push returns ErrNotSupported if the client has disabled push or if push is not supported on the underlying connection.

func (*GzipResponseWriter) Write

func (w *GzipResponseWriter) Write(b []byte) (int, error)

Write appends data to the gzip writer.

func (*GzipResponseWriter) WriteHeader

func (w *GzipResponseWriter) WriteHeader(code int)

WriteHeader just saves the response code until close or GZIP effective writes.

type GzipResponseWriterWithCloseNotify added in v1.0.1

type GzipResponseWriterWithCloseNotify struct {

func (GzipResponseWriterWithCloseNotify) CloseNotify added in v1.0.1

func (w GzipResponseWriterWithCloseNotify) CloseNotify() <-chan bool

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