This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.

The FileSystemFileEntry interface of the File System API represents a file in a file system. It offers properties describing the file's attributes, as well as methods for creating a FileWriter object to write to the file or a File object to read the file.

Because this is a non-standard API, whose specification is not currently on a standards track, it's important to keep in mind that not all browsers implement it, and those that do may implement only small portions of it. Check the Browser compatibility section for details.


Inherits the properties of its parent interface, FileSystemEntry, but has no properties unique to this interface.


Creates a new FileWriter object which allows writing to the file represented by the file system entry.
Creates a new File object which can be used to read the file.

Basic concepts

To write content to file, create a FileWriter object by calling createWriter(). To read a file, obtain a File object representing its contents by calling file().


The following code creates an empty file called "log.txt" (if it doesn't exist) and fills it with the text 'Meow'. Inside the success callback, event handlers are set up for error and writeend events. The text data is written to the file by creating a blob, appending text to it, and passing the blob to FileWriter.write().

function onInitFs(fs) {
  fs.root.getFile('log.txt', {create: true}, function(fileEntry) {

    // Create a FileWriter object for our FileSystemFileEntry (log.txt).
    fileEntry.createWriter(function(fileWriter) {
      fileWriter.onwriteend = function(e) {
        console.log('Write completed.');

      fileWriter.onerror = function(e) {
        console.log('Write failed: ' + e.toString());

      // Create a new Blob and write it to log.txt.
      var bb = new BlobBuilder();
    }, errorHandler);

  }, errorHandler);


window.requestFileSystem(window.TEMPORARY, 1024*1024, onInitFs, errorHandler);


Specification Status Comment
File and Directory Entries API Editor's Draft Draft of proposed API

This API has no official W3C or WHATWG specification.

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support 13 webkit 50 (50) No support No support No support
createWriter() 13 webkit No support[1] No support No support No support
Feature Android Chrome for Android Firefox Mobile (Gecko) IE Phone Opera Mobile Safari Mobile
Basic support No support 0.16webkit 50.0 (50) No support No support No support
createWriter() No support 0.16webkit No support[1] No support No support No support

[1] While the createWriter() method exists in Firefox 50, it is not supported, and immediately reports an NS_ERROR_DOM_SECURITY_ERR error to the error callback.

See also


© 2016 Mozilla Contributors
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.

API File and Directory Entries API File API File System API FileEntry Files Interface Offline offline Reference