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.
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 theonerror
property. load
- Fired when a read has completed successfully.
Also available via theonload
property. loadend
- Fired when a read has completed, successfully or not.
Also available via theonloadend
property. loadstart
- Fired when a read has started.
Also available via theonloadstart
property. progress
- Fired periodically as data is read.
Also available via theonprogress
property.
Specifications
Specification | Status | Comment |
---|---|---|
File API The definition of 'FileReader' in that specification. |
Working Draft | Initial definition |
Browser compatibility
Desktop | Mobile | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
FileReader | 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 |
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
| 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 |
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
| 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 |
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
| 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.