download

Summary

The download() function is used to trigger a file download from JavaScript.

It specifies the contents and name of a new file placed in the browser's download directory. The input can be a URL, String, Blob, or Typed Array of data, or via a dataURL representing the file's data as base64 or url-encoded string. No matter the input format, download() saves a file using the specified file name and mime information in the same manner as a server using a Content-Disposition HTTP header.

Getting and Using

Via NPM/Bower

npm install downloadjs
bower install downloadjs

require("downloadjs")(data, strFileName, strMimeType);

Simple global download function via <script> include

download(data, strFileName, strMimeType);

Included via AMD

require(['path/to/file'], function(download) {
    download(data, strFileName, strMimeType);
});

Parameters

• data - The Blob, File, String, or dataURL containing the soon-to-be File's contents.
• strFileName - The name of the file to be created. Note that older browsers (like FF3.5, Ch5) don't honor the file name you provide, instead they automatically name the downloaded file.
• strMimeType - The MIME content-type of the file to download. While optional, it helps the browser present friendlier information about the download to the user, encouraging them to accept the download.

Example Usage

Plain Text

text string - live demo

download("hello world", "dlText.txt", "text/plain");

text dataURL - live demo

download("data:text/plain,hello%20world", "dlDataUrlText.txt", "text/plain");

text blob - live demo

download(new Blob(["hello world"]), "dlTextBlob.txt", "text/plain");

text url - live demo

download("/robots.txt");

text UInt8 Array - live demo

var str= "hello world", arr= new Uint8Array(str.length);
str.split("").forEach(function(a,b){
  arr[b]=a.charCodeAt();
});

download( arr, "textUInt8Array.txt", "text/plain" );

HTML

html string - live demo

download(document.documentElement.outerHTML, "dlHTML.html", "text/html");

html Blob - live demo

download(new Blob(["hello world".bold()]), "dlHtmlBlob.html", "text/html");

ajax callback - live demo

(note that callback mode won't work on vanilla ajax or with binary files)

$.ajax({
        url: "/download.html",
        success: download.bind(true, "text/html", "dlAjaxCallback.html")
});

Binary Files

image from URL - live demo

download("/diff6.png");

Image via ajax for custom filename - live demo

var x=new XMLHttpRequest();
x.open( "GET", "/diff6.png" , true);
x.responseType="blob";
x.onload= function(e){download(e.target.response, "awesomesauce.png", "image/png");};
x.send();

Compatibility

download.js works with a wide range of devices and browsers.

You can expect it to work for the vast majority of your users, with some common-sense limits:

• Devices without file systems like iPhone, iPad, Wii, et al. have nowhere to save the file to, sorry.
• Android support starts at 4.2 for the built-in browser, though chrome 36+ and firefox 20+ on android 2.3+ work well.
• Devices without Blob support won't be able to download Blobs or TypedArrays
• Legacy devices (no a[download]) support can only download a few hundred kilobytes of data, and can't give the file a custom name.
• Devices without window.URL support can only download a couple megabytes of data
• IE versions of 9 and before are NOT supported because the don't support a[download] or dataURL frame locations.

FAQ

• Can I tell when a download is done/canceled? No.
• How can I style the temporary download link? Define CSS class styles for .download-js-link.
• What's up with Safari? I don't know either but pull requests that improve the situation are welcome.
• Why is my binary file corrupted? Likely: an incorrect MIME or using jQuery ajax, which has no bin support.
• How big of files work? Depends, try yourself: File Echo Demo... I do a 1GB dl routinely on a thinkpad...

Change Log (v4.1)

• 2008 :: landed a FF+Chrome compatible way of downloading strings to local un-named files, upgraded to use a hidden frame and optional mime
• 2012 :: added named files via a[download], msSaveBlob() for IE (10+) support, and window.URL support for larger+faster saves than dataURLs
• 2014 :: added dataURL and Blob Input, bind-toggle arity, and legacy dataURL fallback was improved with force-download mime and base64 support
• 2015 :: converted to amd/commonJS module with browser-friendly fallback
• 2015 :: 4.1 added direct URL downloading via a single URL argument.
• 2016 :: 4.2 added large dataURL support, a more semantic codebase, and hidden temp links
• 2017 :: added support for empty dataURLs
• 20XX :: ???? Considering Zip, Tar, and other multi-file outputs, Blob.prototype.download option, and more, stay tuned folks.