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 aBlob
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 beDONE
. FileReader.readAsArrayBuffer()
- Starts reading the contents of the specified
Blob
, once finished, theresult
attribute contains anArrayBuffer
representing the file's data. FileReader.readAsBinaryString()
- Starts reading the contents of the specified
Blob
, once finished, theresult
attribute contains the raw binary data from the file as a string. FileReader.readAsDataURL()
- Starts reading the contents of the specified
Blob
, once finished, theresult
attribute contains adata:
URL representing the file's data. FileReader.readAsText()
- Starts reading the contents of the specified
Blob
, once finished, theresult
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 theonabort
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
The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.
Update compatibility data on GitHub
Desktop | Mobile | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
FileReader
|
Chrome
Full support 7 |
Edge
Full support 12 |
Firefox Full support 3.6 Full support 3.6 Notes' Prior to Firefox 4, |
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 Full support 3.6 Notes' Prior to Firefox 13, the |
IE Full support 10 Full support 10 Notes' The |
Opera
Full support 11 |
Safari Full support 6 Full support 6 Notes' The |
WebView Android
Full support Yes |
Chrome Android
Full support Yes |
Firefox Android Full support 32 Full support 32 Notes' From Firefox 32 to Firefox 58, the |
Opera Android
Full support 11 |
Safari iOS Full support 6.1 Full support 6.1 Notes' The |
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' |
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' |
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 Full support 32 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
FileReader by Mozilla Contributors is licensed under CC-BY-SA 2.5.