1. JavaScript today is capable of generating a lot of data. The easiest way to deliver multiple files to your users is in a zip file. Instead of wasting server resources and bandwidth you can get the client to do it for you.
  2. Because it's cool!


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See also: the test suite

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Browser support

Opera Firefox Safari Chrome Internet Explorer
Yes Yes Yes Yes Yes
Tested with the latest version Tested with 3.0 / 3.6 / latest version Tested with the latest version Tested with the latest version Tested with IE 6 / 7 / 8 / 9 / 10

While JSZip should work everywhere, the tricky part is to give the zip file to the user.

Browser support for data URI scheme with zip

Opera Firefox Safari Chrome Internet Explorer
7.5+ 3.0+ Yes Yes No
Filename is "" Filename is random alphanumeric with ".part" extension Filename is "Unknown" (no extension) Filename is "" on OSX and Linux, and just "download" on Windows (issue #9) Only supports data URLs for some content. (May be able to use MHTML?)

Filename problems

The biggest issue with JSZip is that the filenames are very awkward, Firefox generates filenames such as (see bugs 367231 and 532230), and Safari isn't much better with just Unknown. Sadly there is no pure Javascript solution (and working in every browsers) to this. However...

Solution-ish: Downloadify

Downloadify uses a small Flash SWF to download files to a user's computer with a filename that you can choose. Doug Neiner has added the dataType option to allow you to pass a zip for downloading. Follow the Downloadify demo with the following changes:

zip = new JSZip();
zip.file("Hello.", "hello.txt");
  data: function(){
    return zip.generate();
  dataType: 'base64'

Other solution-ish: Blob URL / FileSaver / FileSaver.js

With some recent browsers come a new way to download Blobs (a zip file for example) : blob urls. The download attribute on <a> allows you to give the name of the file. Blob urls start to be widely supported but this attribute is currently only supported in Chrome and Firefox (>= 20). See the example. Note : on IE 10/11, using a blob url as a href doesn't seem to work.

var blob = zip.generate({type:"blob"});
myLink.href = window.URL.createObjectURL(blob); = "";

An other solution is the FileSaver interface, created (at the time of writing) with saveAs. This works on Chrome and IE >= 10 (not in compatibility view) but not Firefox.

var blob = zip.generate({type:"blob"});
window.saveAs(blob, "");

Finally, you can use the polyfill FileSaver.js which will use a FileSaver if present or else a blob url.

Usage with Google Gears

Franz Buchinger has written a brilliant tutorial on using JSZip with Google Gears (part 2). If you want to let your Gears users download several files at once I really recommend having a look at some of his examples.

Reading a zip file from an ajax call

When doing an ajax call to get the binary data, the browser will try to interpret the binary as text, corrupting it. The solution is to set the mimetype to 'text/plain; charset=x-user-defined'. This solution works well in all browsers but IE. If you need IE support, please see what is done in the file test/index.html.

An other solution is to use a modern browser (supporting xhr2) : setting xhr.type = 'arraybuffer'; will do the trick, JSZip supports ArrayBuffers. Please see the example.

Reading a local zip file (File API)

JSZip supports (if available in the browser) the File API : reading a local zip file is simple : new JSZip(;. Please see the complete example for more details.


new JSZip() or JSZip()

Description :
The default constructor.
Returns :
A new JSZip.
var zip = new JSZip();
// same as
var zip = JSZip();

new JSZip(data [,options]) or JSZip(data [,options])

Description :
Create a new JSZip file and load an existing zip file. See the documentation of load() for more details and this for the limitations.
Parameters :
data (same types as load()) the content of the zip file to load.
options (Object) options to pass to the load() method..
Returns :
A new JSZip.
new JSZip(zipDataFromXHR, {base64:false});
// same as
JSZip(zipDataFromXHR, {base64:false});
// same as
var zip = new JSZip();
zip.load(zipDataFromXHR, {base64:false});


Description :
Get a file with the specified name.
Parameters :
name (String) the name of the file.
Returns :
The file if any, null otherwise. The file has the following structure :
var zip = new JSZip();
zip.file("file.txt", "content");

zip.file("file.txt").name // "file.txt"
zip.file("file.txt").asText() // "content"
zip.file("file.txt").options.dir // false

// utf8 example
var zip = new JSZip(zipFromAjaxWithUTF8);
zip.file("amount.txt").asText() // "€15"
zip.file("amount.txt").asArrayBuffer() // an ArrayBuffer containing €15
zip.file("amount.txt").asUint8Array() // an Uint8Array containing €15


Description :
Search a file in the current folder and subfolders with a regular expression. The regex is tested against the relative filename.
Parameters :
regex (RegExp) the regex to use.
Returns :
An array of matching files (an empty array if none matched).
var zip = new JSZip();
zip.file("file1.txt", "content");
zip.file("file2.txt", "content");

zip.file(/file/); // array of size 2

// example with a relative path :
var folder = zip.folder("sub");
  .file("file3.txt", "content")  // relative path from folder : file3.txt
  .file("file4.txt", "content"); // relative path from folder : file4.txt

folder.file(/file/);  // array of size 2
folder.file(/^file/); // array of size 2, the relative paths start with file

// arrays contain objects in the form:
// {name: "file2.txt", dir: false, asText : function () {...}, ...}

file(name, data [,options])

Description :
Add a file to the zip file.
Parameters :
name (String) the name of the file.
data (String/ArrayBuffer/Uint8Array/Buffer) the content of the file.
options (Object) the options :
  • base64 (boolean) set to true if the data is base64 encoded. For example image data from a <canvas> element. Plain text and HTML do not need this option.
  • binary (boolean) defaults to true if the data is base64 encoded, false otherwise. If set to false then UTF-8 characters will be encoded. If the data is an ArrayBuffer or an Uint8Array, this will be set to true.
  • date (Date) use it to specify the last modification date. If not set the current date is used.
  • compression (String), default null. If set, specifies the file compression method to use. If not, the default file compression is used, cf generate(options).
  • optimizedBinaryString (boolean), default false. Set it to true if (and only if) the input is a string and has already been prepared with a 0xFF mask.
Returns :
A JSZip object, for chaining.
zip.file("Hello.txt", "Hello World\n");
zip.file("smile.gif", "R0lGODdhBQAFAIACAAAAAP/eACwAAAAABQAFAAACCIwPkWerClIBADs=", {base64: true});
zip.file("magic.txt", "U2VjcmV0IGNvZGU=", {base64: true, binary: false});
zip.file("Xmas.txt", "Ho ho ho !", {date : new Date("December 25, 2007 00:00:01")});
zip.file("folder/file.txt", "file in folder");

zip.file("animals.txt", "dog,platypus\n").file("people.txt", "james,sebastian\n");

// result : Hello.txt, smile.gif, magic.txt, Xmas.txt, animals.txt, people.txt,
// folder/, folder/file.txt


Description :
Add a directory to the zip file.
Parameters :
name (String) the name of the directory.
Returns :
a new JSZip (for chaining), with the new folder as root.
zip.folder("css").file("style.css", "body {background: #FF0000}");
// or specify an absolute path (using forward slashes)
zip.file("css/font.css", "body {font-family: sans-serif}")

// result : images/, css/, css/style.css, css/font.css


Description :
Search a subdirectory.
Search a subdirectory in the current directory with a regular expression. The regex is tested against the relative path.
Parameters :
regex (RegExp) the regex to use.
Returns :
An array of matching folders (an empty array if none matched).
var zip = new JSZip();

zip.folder(/videos/); // array of size 2

zip.folder("home/Jean").folder(/^vid/); // array of 1


Delete a file or folder.

Description :
Delete a file or folder (recursively).
Parameters :
name (String) the name of the file/folder to delete.
Returns :
The current JSZip object.
var zip = new JSZip();
zip.file("Hello.txt", "Hello World\n");
zip.file("temp.txt", "nothing").remove("temp.txt");
// result : Hello.txt

zip.folder("css").file("style.css", "body {background: #FF0000}");
//result : empty zip


Description :
Generates the complete zip file.
Parameters :
options (Object) the options to generate the zip file :
  • base64 (boolean) deprecated, use "type" instead. false to get the result as a raw byte string. Default : true, encode as base64.
  • compression (String) the default file compression method to use. "STORE" (no compression) by default, you can use "DEFLATE" or write your own.
  • type (String) the type of zip to return. The possible values are :
    • base64 (default) : the result will be a string, the binary in a base64 form.
    • string : the result will be a string in "binary" form, 1 byte per char.
    • uint8array : the result will be a Uint8Array containing the zip. This requires a compatible browser.
    • arraybuffer : the result will be a ArrayBuffer containing the zip. This requires a compatible browser.
    • blob : the result will be a Blob containing the zip. This requires a compatible browser.
    • nodebuffer : the result will be a nodejs Buffer containing the zip. This requires nodejs.
Returns :
The generated zip file.
HTML5 note : when using type = "uint8array", "arraybuffer" or "blob", be sure to check if the browser supports it (you can use This method will throw an exception otherwise.
content = zip.generate(); // base64
var blobLink = document.getElementById('blobLink'); = "";
blobLink.href = window.URL.createObjectURL(
content = zip.generate({type:"string"});
for (var c = 0; c < content.length; c++) {
    // do other things

load(data, options)

Description :
Read an existing zip and merge the data in the current JSZip object. This technique has some limitations, see below.
Parameters :
data (String/ArrayBuffer/Uint8Array/Buffer) the zip file
options (Object) the options to load the zip file :
  • base64 (boolean) true if the data is base64 encoded, false for binary. Default : false.
  • checkCRC32 (boolean) true if the read data should be checked against its CRC32. Default : false.
  • optimizedBinaryString (boolean), default false. Set it to true if (and only if) the input is a string and has already been prepared with a 0xFF mask.
Returns :
The current JSZip object.
var zip = new JSZip();
Zip features supported by this method
Zip features not (yet) supported


Description :
Filter nested files/folders with the specified function.
Parameters :
predicate (function) the predicate to use : function (relativePath, file) {...} It takes 2 arguments : the relative path and the file.
  • relativePath (String) The filename and its path, reliatively to the current folder.
  • file (Object) The file being tested. Like the result of file(name), the file has the form {name:"...", options:{...}, asText:function,...}.
  • Return true if the file should be included, false otherwise.
Returns :
An array of matching elements.
var zip = new JSZip().folder("dir");
zip.file("readme.txt", "content");
zip.filter(function (relativePath, file){
  // relativePath == "readme.txt"
  // file = {name:"dir/readme.txt",options:{...},asText:function}
  return true/false;

If the browser supports them, JSZip can take advantage of some new features : ArrayBuffer, Blob, Uint8Array. To know if JSZip can use them, you can check the object. It contains the following properties :

Loading zip files, limitations

Not supported features

All the features of zip files are not supported. Classic zip files will work but encrypted zip, multi-volume, etc are not supported and the load() method will throw an Error.

ZIP64 and 32bit integers

ZIP64 files can be loaded, but only if the zip file is not "too big". ZIP64 uses 64bits integers but Javascript represents all numbers as 64-bit double precision IEEE 754 floating point numbers (see section 8.5). So, we have 53bits for integers and bitwise operations treat everything as 32bits. So if all the 64bits integers can fit into 32 bits integers, everything will be fine. If it's not the case, you will have other problems anyway (see next limitation).

Performance issues

An other limitation comes from the browser (and the machine running the browser). A compressed zip file of 10MB is "easily" opened by firefox/chrome/opera/IE10 but will crash older IE. Also keep in mind that strings in javascript are encoded in UTF-16 : a 10MB ascii text file will take 20MB of memory.

If you're having performance issues, please consider the following :

The output zip will differ from the input zip

Reading and generating a zip file won't give you back the same file. Some data are discarded (file metadata) and other are added (subfolders).


Migrating Guide

Fromt 2.0.0 to 2.1.0

From 1.x to 2.x

Example for the data attribute :
// before

// after

Anything else?


MIT license or GPLv3



See the migrating guide when updating the library!



Stuart Knightley, with contributions from:

Contact and bugs