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.

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.

Specifications

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

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
Basic supportChrome Full support 7Edge Full support YesFirefox Full support 3.6
Notes
Full support 3.6
Notes
Notes Prior to Firefox 4, Blob parameters were File parameters.
IE Full support 10Opera Full support 11Safari Full support 6WebView Android ? Chrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 32Opera Android Full support 11Safari iOS Full support 6.1Samsung Internet Android ?
Available in workersChrome Full support YesEdge Full support YesFirefox Full support 46IE No support NoOpera Full support 11Safari No support NoWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 46Opera Android Full support 11Safari iOS No support NoSamsung Internet Android ?
abortChrome Full support 7Edge Full support YesFirefox Full support 3.6IE Full support 10Opera Full support 11Safari Full support 6WebView Android ? Chrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 32Opera Android Full support 11Safari iOS Full support 6.1Samsung Internet Android ?
errorChrome Full support 7Edge Full support YesFirefox 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 11Safari Full support 6
Notes
Full support 6
Notes
Notes The error property returns a DOMError object.
WebView Android ? Chrome Android Full support YesEdge Mobile Full support YesFirefox 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 11Safari iOS Full support 6.1
Notes
Full support 6.1
Notes
Notes The error property returns a DOMError object.
Samsung Internet Android ?
onabortChrome Full support 7Edge Full support YesFirefox Full support 3.6IE Full support 10Opera Full support 11Safari Full support 6WebView Android ? Chrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 32Opera Android Full support 11Safari iOS Full support 6.1Samsung Internet Android ?
onerrorChrome Full support 7Edge Full support YesFirefox Full support 3.6IE Full support 10Opera Full support 11Safari Full support 6WebView Android ? Chrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 32Opera Android Full support 11Safari iOS Full support 6.1Samsung Internet Android ?
onloadChrome Full support 7Edge Full support YesFirefox Full support 3.6IE Full support 10Opera Full support 11Safari Full support 6WebView Android ? Chrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 32Opera Android Full support 11Safari iOS Full support 6.1Samsung Internet Android ?
onloadendChrome Full support 7Edge Full support YesFirefox Full support 3.6IE Full support 10Opera Full support 11Safari Full support 6WebView Android ? Chrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 32Opera Android Full support 11Safari iOS Full support 6.1Samsung Internet Android ?
onprogressChrome Full support 7Edge Full support YesFirefox Full support 3.6IE Full support 10Opera Full support 11Safari Full support 6WebView Android ? Chrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 32Opera Android Full support 11Safari iOS Full support 6.1Samsung Internet Android ?
readyStateChrome Full support 7Edge Full support YesFirefox Full support 3.6IE Full support 10Opera Full support 11Safari Full support 6WebView Android ? Chrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 32Opera Android Full support 11Safari iOS Full support 6.1Samsung Internet Android ?
readAsArrayBufferChrome Full support 7Edge Full support YesFirefox Full support 3.6IE Full support 10Opera Full support 12Safari Full support 6WebView Android ? Chrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 32Opera Android Full support 12Safari iOS Full support 6.1Samsung Internet Android ?
readAsBinaryStringChrome Full support 7Edge Full support YesFirefox Full support 3.6IE Full support 10Opera Full support 11Safari Full support 6WebView Android ? Chrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 32Opera Android Full support 11Safari iOS Full support 6.1Samsung Internet Android ?
readAsDataURLChrome Full support 7Edge Full support YesFirefox Full support 3.6IE Full support 10Opera Full support 11Safari Full support 6WebView Android ? Chrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 32Opera Android Full support 11Safari iOS Full support 6.1Samsung Internet Android ?
readAsTextChrome Full support 7Edge Full support YesFirefox Full support 3.6IE Full support 10Opera Full support 11Safari Full support 6WebView Android ? Chrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 32Opera Android Full support 11Safari iOS Full support 6.1Samsung Internet Android ?
resultChrome Full support 7Edge Full support YesFirefox Full support 3.6IE Full support 10Opera Full support 11Safari Full support 6WebView Android ? Chrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 32Opera Android Full support 11Safari iOS Full support 6.1Samsung Internet Android ?

Legend

Full support  
Full support
No support  
No support
Compatibility unknown  
Compatibility unknown
See implementation notes.
See implementation notes.

See also