simple wrapper on top of express.static, that allows serving pre-gziped files

Usage no npm install needed!

<script type="module">
  import expressStaticGzip from '';



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Provides a small layer on top of serve-static, which allows to serve pre-gzipped files. Supports brotli and allows configuring any other compression you can think of as well.

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For the express-static-gzip middleware to work properly you need to first ensure that you have all files gzipped (or compressed with your desired algorithm) which you want to serve as a compressed version to the browser. Simplest use case is to either have a folder with only .gz files, or you have a folder with the .gz files next to the original files. Same goes for other compressions.


    $ npm install express-static-gzip

Changelog for v2.0

  • Even so this is a mayor release, this should be fully backwards compatible and should not have any breaking change to v1.1.3.

  • Moved all options for serveStatic in its own section (serveStatic) to prevent collisions when setting up your static fileserving middleware.

  • For backwards compatibility all root options that apply to serveStatic will be copied to the new serveStatic section, except if you have set values there already (no overwrite). Here is a small example of this behaviour:

        enableBrotli: true,         // not a serverStatic option, will not be moved
        maxAge: 123,                // not copied, as already present.
        index: 'main.js',           // copied to serveStatic section
        serveStatic: {
            maxAge: 234,            // will be kept 
            cacheControl: false     // will be kept as well

    In the above scenario serveStatic will use cacheControl: false, index: 'main.js', maxAge:234.


In case you just want to serve gzipped files only, this simple example would do:

var express = require("express");
var expressStaticGzip = require("express-static-gzip");
var app = express();

app.use("/", expressStaticGzip("/my/rootFolder/"));

While gzip compression is always enabled you now have the choice to add other types of compressions using the options object. Currently brotli can be enabled using the options.enableBrotli flag. All other compressions need to be added by passing an array to options.customCompressions. The options.serveStatic section is passed to the underlying serve-static middleware, in case you want to configure this one as well.

The following example will show how to add brotli and deflate (with file extension .zz) to the middleware (it will still support gzip) and force brotli to be used if available (orderPreference):

var express = require('express');
var expressStaticGzip = require('express-static-gzip');
var app = express();

app.use('/', expressStaticGzip('/my/rootFolder/', {
    enableBrotli: true,
    customCompressions: [{
        encodingName: 'deflate',
        fileExtension: 'zz'
    orderPreference: ['br']

Compressions are selected in the following order if a file is requested from the middleware:

  • any encoding listed in option.orderPreference and supported by the client
  • in order of the requests 'accept-encoding' header content (if no quality if provided)
  • in order of their respective quality (if provided)
  • in case of a wildcard '*', the compression is selected in alphabetical order (for now)
  • plain file (in case no compression exists or none is matching the browsers accept-encoding header)

For more details see here, but not all of it is implemented at the moment.

When the middleware is created it will check the given root folder and all subfolders for files matching the registered compression. Adding files later to the folder will not be recognized by the middleware.

Available options

  • enableBrotli: boolean (default: false)

    Enables support for the brotli compression, using file extension 'br' (e.g. '').

  • index: boolean | string (default: 'index.html')

    By default this module will send "index.html" files in response to a request on a directory (url ending with '/'). To disable this set false or to supply a new index file pass a string (like 'index.htm').

  • customCompressions: [{encodingName: string, fileExtension: string}]

    Using this option, you can add any other compressions you would like. encodingName will be checked against the Accept-Header. fileExtension is used to find files using this compression. fileExtension does not require a dot (not '.gz', but 'gz').

  • orderPreference: string[]

    This options allows overwriting the client's requested encoding preference (see MDN) with a server side preference. Any encoding listed in orderPreference will be used first (if supported by the client) before falling back to the client's supported encodings. The order of entries in orderPreference is taken into account.

  • serveStatic: ServeStaticOptions

    This will be forwarded to the underlying serveStatic instance used by expressStaticGzip

Behavior warning

In default mode a request for "/" or "<somepath>/" will serve index.html as compressed version. This could lead to complications if you are serving a REST API from the same path, when express-server-static is registered before your API.

One solution would be to register express-server-static last. Otherwise you can set options.index to false:

app.use("/", expressStaticGzip("/my/rootFolder/", { index: false }));

Because this middleware was developed for a static production server use case to maximize performance, it is designed to look up and cache the compressed files corresponding to uncompressed file names on startup. This means that it will not be aware of compressed files being added or removed later on.


In case you have the following basic file structure

  • rootFolder
    • index.html
    • index.html.gz
    • test.html.gz
    • main.js

and you use set the enableBrotli flag to true, express-static-gzip will answer GET requests like this:

GET / >>> /my/rootFolder/

GET /index.html >>> /my/rootFolder/

GET /test.html >>> /my/rootFolder/test.html.gz

GET /main.js >>> /my/rootFolder/main.js