File objects are generally retrieved from a
FileList object returned as a result of a user selecting files using the
<input> element, from a drag and drop operation's
DataTransfer object, or from the
mozGetAsFile() API on an
HTMLCanvasElement. In Gecko, privileged code can create
File objects representing any local file without user interaction (see Gecko notes for more information.)
File object is specific kind of a
Blob, and can be used in any context that a Blob can. In particular,
XMLHttpRequest.send() accept both
See Using files from web applications for more information and examples.
- The last modified
Dateof the file referenced by the
- The name of the file referenced by the
File interface also inherits properties from the
- A boolean value, indicating whether the
Blob.close()method has been called on the blob. Closed blobs can not be read.
- The size, in bytes, of the data contained in the
- A string indicating the MIME type of the data contained in the
Blob. If the type is unknown, this string is empty.
File interface doesn't define any methods, but inherits methods from the
- Closes the blob object, possibly freeing underlying resources.
Blob.slice([start[, end[, contentType]]])
- Returns a new
Blobobject containing the data in the specified range of bytes of the source
|File API||Working Draft||Initial definition|
|Feature||Chrome||Firefox (Gecko)||Internet Explorer||Opera||Safari (WebKit)|
|Basic support||13||3.0 (1.9)
|Feature||Android||Firefox Mobile (Gecko)||IE Phone||Opera Mobile||Safari Mobile|
|basic support||No support||25||No support||11.1||6.0|
 Non-standard implementation.
- In Gecko, you can use this API from within chrome code. See Using the DOM File API in chrome code for details. To use it from chrome code, JSM and Bootstrap scope, you have to import it using
- Starting from Gecko 6.0 (Firefox 6.0 / Thunderbird 6.0 / SeaMonkey 2.3), privileged code (such as extensions) can pass an
nsIFileobject to the DOM
Fileconstructor to specify the file to reference.
- Starting from Gecko 8.0 (Firefox 8.0 / Thunderbird 8.0 / SeaMonkey 2.5), you can use
new Fileto create
Fileobjects from XPCOM component code instead of having to instantiate the
nsIDOMFileobject directly. The constructor takes, in contrast to
Blob, as second argument the filename. The filename can be any String.
new File( Array parts, String filename, BlobPropertyBag properties );
- The following non-standard properties and methods were removed in Gecko 7 (Firefox 7.0 / Thunderbird 7.0 / SeaMonkey 2.4):
File.getAsText(string encoding)(bug 661876). Standard properties
Blob.size, and methods on
FileReadershould be used instead.