Web/API/FileReader

From Get docs


The FileReader object lets web applications asynchronously read the contents of files (or raw data buffers) stored on the user's computer, using File or Blob objects to specify the file or data to read.

File objects may be obtained 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.

Important note: FileReader is used to read file content from the user's (remote) system in secure ways only. It cannot be used to simply read a file by pathname from a file system. To read files by pathname in JavaScript, standard Ajax solutions should be used to do server-side file reading, with CORS permission if reading cross-domain.


Note: This feature is available in Web Workers.

Constructor

FileReader()
Returns a newly constructed FileReader.

See Using files from web applications for details and examples.

Properties

FileReader.error Read only
A DOMException representing the error that occurred while reading the file.
FileReader.readyState Read only
A number indicating the state of the FileReader. This is one of the following:
EMPTY 0 No data has been loaded yet.
LOADING 1 Data is currently being loaded.
DONE 2 The entire read request has been completed.
FileReader.result Read only
The file's contents. This property is only valid after the read operation is complete, and the format of the data depends on which of the methods was used to initiate the read operation.

Event handlers

FileReader.onabort
A handler for the abort event. This event is triggered each time the reading operation is aborted.
FileReader.onerror
A handler for the error event. This event is triggered each time the reading operation encounter an error.
FileReader.onload
A handler for the load event. This event is triggered each time the reading operation is successfully completed.
FileReader.onloadstart
A handler for the loadstart event. This event is triggered each time the reading is starting.
FileReader.onloadend
A handler for the loadend event. This event is triggered each time the reading operation is completed (either in success or failure).
FileReader.onprogress
A handler for the progress event. This event is triggered while reading a Blob content.

As FileReader inherits from EventTarget, all those events can also be listened for by using the addEventListener method.


Methods

FileReader.abort()
Aborts the read operation. Upon return, the readyState will be DONE.
FileReader.readAsArrayBuffer()
Starts reading the contents of the specified Blob, once finished, the result attribute contains an ArrayBuffer representing the file's data.
FileReader.readAsBinaryString()
Starts reading the contents of the specified Blob, once finished, the result attribute contains the raw binary data from the file as a string.
FileReader.readAsDataURL()
Starts reading the contents of the specified Blob, once finished, the result attribute contains a data: URL representing the file's data.
FileReader.readAsText()
Starts reading the contents of the specified Blob, once finished, the result attribute contains the contents of the file as a text string. An optional encoding name can be specified.

Events

Listen to these events using addEventListener() or by assigning an event listener to the oneventname property of this interface.

abort
Fired when a read has been aborted, for example because the program called FileReader.abort(). Also available via the onabort property.
error
Fired when the read failed due to an error. Also available via the onerror property.
load
Fired when a read has completed successfully. Also available via the onload property.
loadend
Fired when a read has completed, successfully or not. Also available via the onloadend property.
loadstart
Fired when a read has started. Also available via the onloadstart property.
progress
Fired periodically as data is read. Also available via the onprogress property.

Specifications

Specification Status Comment
File APIThe definition of 'FileReader' in that specification. Working Draft Initial definition

Browser compatibility

Update compatibility data on GitHub

Desktop Mobile
Chrome Edge Firefox Internet Explorer Opera Safari Android webview Chrome for Android Firefox for Android Opera for Android Safari on iOS Samsung Internet
FileReader Chrome

Full support 7

Edge

Full support 12

Firefox Full support 3.6

Notes'

Full support 3.6

Notes'

Notes' Prior to Firefox 4, Blob parameters were File parameters.

IE

Full support 10

Opera

Full support 11

Safari

Full support 6

WebView Android

Full support ≤37

Chrome Android

Full support 18

Firefox Android

Full support 32

Opera Android

Full support 11

Safari iOS

Full support 6.1

Samsung Internet Android

Full support 1.0

abort Chrome

Full support 7

Edge

Full support 12

Firefox

Full support 3.6

IE

Full support 10

Opera

Full support 11

Safari

Full support 6

WebView Android

Full support Yes

Chrome Android

Full support Yes

Firefox Android

Full support 32

Opera Android

Full support 11

Safari iOS

Full support 6.1

Samsung Internet Android

Full support Yes

abort event Chrome

Full support Yes

Edge

Full support 12

Firefox

Full support Yes

IE

Full support Yes

Opera

Full support Yes

Safari

Full support Yes

WebView Android

Full support Yes

Chrome Android

Full support Yes

Firefox Android

Full support Yes

Opera Android

Full support Yes

Safari iOS

Full support Yes

Samsung Internet Android

Full support Yes

error Chrome

Full support 7

Edge

Full support 12

Firefox Full support 3.6

Notes'

Full support 3.6

Notes'

Notes' Prior to Firefox 13, the error property returned a FileError object. Notes' From Firefox 13 to Firefox 58, the error property returned a DOMError object. Notes' From Firefox 58, the error property returns a DOMException object.

IE Full support 10

Notes'

Full support 10

Notes'

Notes' The error property returns a DOMError object.

Opera

Full support 11

Safari Full support 6

Notes'

Full support 6

Notes'

Notes' The error property returns a DOMError object.

WebView Android

Full support Yes

Chrome Android

Full support Yes

Firefox Android Full support 32

Notes'

Full support 32

Notes'

Notes' From Firefox 32 to Firefox 58, the error property returned a DOMError object. Notes' From Firefox 58, the error property returns a DOMException object.

Opera Android

Full support 11

Safari iOS Full support 6.1

Notes'

Full support 6.1

Notes'

Notes' The error property returns a DOMError object.

Samsung Internet Android

Full support Yes

error event Chrome

Full support Yes

Edge

Full support 12

Firefox

Full support Yes

IE

Full support Yes

Opera

Full support Yes

Safari

Full support Yes

WebView Android

Full support Yes

Chrome Android

Full support Yes

Firefox Android

Full support Yes

Opera Android

Full support Yes

Safari iOS

Full support Yes

Samsung Internet Android

Full support Yes

load event Chrome

Full support Yes

Edge

Full support 12

Firefox

Full support Yes

IE

Full support Yes

Opera

Full support Yes

Safari

Full support Yes

WebView Android

Full support Yes

Chrome Android

Full support Yes

Firefox Android

Full support Yes

Opera Android

Full support Yes

Safari iOS

Full support Yes

Samsung Internet Android

Full support Yes

loadend event Chrome

Full support Yes

Edge

Full support 12

Firefox

Full support Yes

IE

Full support Yes

Opera

Full support Yes

Safari

Full support Yes

WebView Android

Full support Yes

Chrome Android

Full support Yes

Firefox Android

Full support Yes

Opera Android

Full support Yes

Safari iOS

Full support Yes

Samsung Internet Android

Full support Yes

loadstart event Chrome

Full support Yes

Edge

Full support 12

Firefox Full support 79


Full support 79


No support ? — 79

Notes'

Notes' loadstart event dispatches synchronously (should be asynchronously as per spec).

IE

Full support Yes

Opera

Full support Yes

Safari

Full support Yes

WebView Android

Full support Yes

Chrome Android

Full support Yes

Firefox Android Full support 79


Full support 79


No support ? — 79

Notes'

Notes' loadstart event dispatches synchronously (should be asynchronously as per spec).

Opera Android

Full support Yes

Safari iOS

Full support Yes

Samsung Internet Android

Full support Yes

onabort Chrome

Full support 7

Edge

Full support 12

Firefox

Full support 3.6

IE

Full support 10

Opera

Full support 11

Safari

Full support 6

WebView Android

Full support Yes

Chrome Android

Full support Yes

Firefox Android

Full support 32

Opera Android

Full support 11

Safari iOS

Full support 6.1

Samsung Internet Android

Full support Yes

onerror Chrome

Full support 7

Edge

Full support 12

Firefox

Full support 3.6

IE

Full support 10

Opera

Full support 11

Safari

Full support 6

WebView Android

Full support Yes

Chrome Android

Full support Yes

Firefox Android

Full support 32

Opera Android

Full support 11

Safari iOS

Full support 6.1

Samsung Internet Android

Full support Yes

onload Chrome

Full support 7

Edge

Full support 12

Firefox

Full support 3.6

IE

Full support 10

Opera

Full support 11

Safari

Full support 6

WebView Android

Full support ≤37

Chrome Android

Full support 18

Firefox Android

Full support 32

Opera Android

Full support 11

Safari iOS

Full support 6.1

Samsung Internet Android

Full support 1.0

onloadend Chrome

Full support 7

Edge

Full support 12

Firefox

Full support 3.6

IE

Full support 10

Opera

Full support 11

Safari

Full support 6

WebView Android

Full support Yes

Chrome Android

Full support Yes

Firefox Android

Full support 32

Opera Android

Full support 11

Safari iOS

Full support 6.1

Samsung Internet Android

Full support Yes

onprogress Chrome

Full support 7

Edge

Full support 12

Firefox

Full support 3.6

IE

Full support 10

Opera

Full support 11

Safari

Full support 6

WebView Android

Full support Yes

Chrome Android

Full support Yes

Firefox Android

Full support 32

Opera Android

Full support 11

Safari iOS

Full support 6.1

Samsung Internet Android

Full support Yes

progress event Chrome

Full support Yes

Edge

Full support 12

Firefox

Full support Yes

IE

Full support Yes

Opera

Full support Yes

Safari

Full support Yes

WebView Android

Full support Yes

Chrome Android

Full support Yes

Firefox Android

Full support Yes

Opera Android

Full support Yes

Safari iOS

Full support Yes

Samsung Internet Android

Full support Yes

readAsArrayBuffer Chrome

Full support 7

Edge

Full support 12

Firefox

Full support 3.6

IE

Full support 10

Opera

Full support 12

Safari

Full support 6

WebView Android

Full support ≤37

Chrome Android

Full support 18

Firefox Android

Full support 32

Opera Android

Full support 12

Safari iOS

Full support 6.1

Samsung Internet Android

Full support 1.0

readAsBinaryString Chrome

Full support 7

Edge

Full support 12

Firefox

Full support 3.6

IE

No support No

Opera

Full support 11

Safari

Full support 6

WebView Android

Full support ≤37

Chrome Android

Full support 18

Firefox Android

Full support 32

Opera Android

Full support 11

Safari iOS

Full support 6.1

Samsung Internet Android

Full support 1.0

readAsDataURL Chrome

Full support 7

Edge

Full support 12

Firefox

Full support 3.6

IE

Full support 10

Opera

Full support 11

Safari

Full support 6

WebView Android

Full support ≤37

Chrome Android

Full support 18

Firefox Android Full support 32

Notes'

Full support 32

Notes'

Notes' Using the camera in Android 8.x raises an exception. See bug 1511083.

Opera Android

Full support 11

Safari iOS

Full support 6.1

Samsung Internet Android

Full support 1.0

readAsText Chrome

Full support 7

Edge

Full support 12

Firefox

Full support 3.6

IE

Full support 10

Opera

Full support 11

Safari

Full support 6

WebView Android

Full support ≤37

Chrome Android

Full support 18

Firefox Android

Full support 32

Opera Android

Full support 11

Safari iOS

Full support 6.1

Samsung Internet Android

Full support 1.0

readyState Chrome

Full support 7

Edge

Full support 12

Firefox

Full support 3.6

IE

Full support 10

Opera

Full support 11

Safari

Full support 6

WebView Android

Full support Yes

Chrome Android

Full support Yes

Firefox Android

Full support 32

Opera Android

Full support 11

Safari iOS

Full support 6.1

Samsung Internet Android

Full support Yes

result Chrome

Full support 7

Edge

Full support 12

Firefox

Full support 3.6

IE

Full support 10

Opera

Full support 11

Safari

Full support 6

WebView Android

Full support Yes

Chrome Android

Full support Yes

Firefox Android

Full support 32

Opera Android

Full support 11

Safari iOS

Full support 6.1

Samsung Internet Android

Full support Yes

Available in workers Chrome

Full support Yes

Edge

Full support ≤18

Firefox

Full support 46

IE

No support No

Opera

Full support 11

Safari

No support No

WebView Android

Full support Yes

Chrome Android

Full support Yes

Firefox Android

Full support 46

Opera Android

Full support 11

Safari iOS

No support No

Samsung Internet Android

Full support Yes

Legend

Full support  
Full support
No support  
No support
See implementation notes.'
See implementation notes.


See also