ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel

How-To Use HTML5 File System Access API

Updated on April 26, 2013

One of the major roadblocks to using the browser as a true thin client for applications has been the lack of access to the file system. In the past a developer could access the file System using JScript (the Microsoft Javascript variant) in Internet Explorer by accessing the FileSystemObject API. However this was off limits to the other browsers until now.

Along with offline capabilities for web applications, HTML5 API offers the capability to access the file system to read and write to files. This is possible through the new File API in HTML5 (

Through the File API the following operations are possible:

FileList represents a list of files located on a file system;
Blob provides an interface to binary files;
File, another interface, includes information on a file’s attributes;
FileReader allows for reading from a file;
FileError and FileException provides the means to handle errors and exceptions, and finally
URI Scheme which provides an interface to binary files from a web application.

A second specification, File:Writer is also under consideraton at the w3c to allow web applications access to write to files in a sandbox.

The File: Writer API offers the following operations:

BlobBuilder, an interface to build a blob from a string;
FileSaver, provides a means to write to a file and and event model to interact with files;
FileWriter expands on the FileSaver interface with a richer set of operations;
FileWriterSync, provides operations to interact asynchronuously with files through a Web Worker.

As you might imagine, not all the browsers are implementing this APIs simultaneously but all the major vendors have these specifications on their development roadmap. At the time of this writing only Google Chrome 13 fully supports both specifications. Firefox 7 will support the File:Writer specification and it already supports the File API. Internet Explorer will support the APIs with in version 10 and Opera will implements these APIs in version 12.

These APIs are designed to be used in conjunction with the XMLHttpRequest2 object and other HTML5 APIs and technologies.

For example:

// To access the sandboxed file system (meaning two or more apps canât access each others files) you need to initialize the FileSystem object:

if('webkitRequestFileSystem' in window)
window.requestFileSystem = window.webkitRequestFileSystem;
window.requestFileSystem(window.PERSISTENT, 10*1024*1024, onSuccess, onError);
}else if('moz_requestFileSystem' in window)
	window.requestFileSystem = window.moz_requestFileSystem;
	window.requestFileSystem(window.PERSISTENT, 10*1024*1024, onSuccess, onError);
	//this browser is not suported
function onSuccess(fs) { //do something};
function onError(e) {// handle the error};

In the above example, the first parameter of the requestFileSystem can either window.PERSISTENT or window.TEMPORARY. The temporary access may remove the files that are created or read after the session is finished, persistent, as the name implies doesn’t remove any files.

Also in the above example I am assuming that this is a web application and not an offline app and since Google Chrome and Firefox have started prefixing their APIs, you will need to check the user agent in your initialization. Otherwise if its an offline app you would simply initialize the the file system for either browser.

Read from a File

Next to read from a file

You get access to a file through the FileEntry interace. So after getting a handle on the file system, in the onSuccess callback function you can get a file and open it for reading like so:

function onSuccess(fs)
	fs.root.getFile('helloWorld.txt', null, function(fileEntry){
				var reader = new FileReader();


Write to a File

To write to a file you need a create a BlobBuilder. In Chrome as of version 12 you need to prefix the interface name with “WebKit” like WebKitBlobBuilder. This is also true for Safari. For Firefox, you would need to add the prefix “Moz” like so : MozBlobBuilder. I guess browser vendor want to keep us developers from getting bored.

function onSuccess(fs)
	fs.root.getFile('storage.txt', {create:true}, function(fileEntry){
				f.onwriteend = function(event) {};
				f.onerror = function(err) {};
				BlobBuilder = window.BlobBuilder || window.WebKitBlobBuilder || window.MozBlobBuilder;
				var writer = new BlobBuilder();
				writer.append('some text');


The HTML5 File API holds a lot of promise for developers, especially for offline or installable apps. For web applications that has a persistent data store, I don’t really see the point. Anyway the API has a lot of interesting features that I invite to explore further at w3c.


    0 of 8192 characters used
    Post Comment

    • klanguedoc profile imageAUTHOR

      Kevin Languedoc 

      5 years ago from Canada

      I'll check it out

    • profile image


      5 years ago

      The function "onSuccess"

      Normal right hand bracket missing. Suppose it should be just before the last curly bracket. At least putting one get rid of the error message

    • klanguedoc profile imageAUTHOR

      Kevin Languedoc 

      6 years ago from Canada

      The fs is the file system object

    • profile image


      6 years ago

      what's fs in onSuccess function


    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

    For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at:

    Show Details
    HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
    LoginThis is necessary to sign in to the HubPages Service.
    Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
    AkismetThis is used to detect comment spam. (Privacy Policy)
    HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
    HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
    Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
    CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
    Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the or domains, for performance and efficiency reasons. (Privacy Policy)
    Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
    Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
    Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
    Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
    Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
    VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
    PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
    Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
    MavenThis supports the Maven widget and search functionality. (Privacy Policy)
    Google AdSenseThis is an ad network. (Privacy Policy)
    Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
    Index ExchangeThis is an ad network. (Privacy Policy)
    SovrnThis is an ad network. (Privacy Policy)
    Facebook AdsThis is an ad network. (Privacy Policy)
    Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
    AppNexusThis is an ad network. (Privacy Policy)
    OpenxThis is an ad network. (Privacy Policy)
    Rubicon ProjectThis is an ad network. (Privacy Policy)
    TripleLiftThis is an ad network. (Privacy Policy)
    Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
    Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
    Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
    Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
    ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
    Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)