The FileReader result property returns 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.


var file = instanceOfFileReader.result


An appropiate string or ArrayBuffer based on which of the reading methods was used to initiate the read operation. The value is null if the reading is not yet complete or was unsuccessful.

The result types are described below.

Method Description
readAsArrayBuffer() The result is a JavaScript ArrayBuffer containing binary data.
readAsBinaryString() The result contains the raw binary data from the file in a string.
readAsDataURL() The result is a string with a data: URL representing the file's data.
readAsText() The result is text in a string.


This example presents a function, read(), which reads a file from a file input. It works by creating a FileReader object and creating a listener for load events such that when then file is read, the result is obtained and passed to the callback function provided to read().

The content is handled as raw text data.

var fileInput = document.querySelector('input[type="file"]');

function read(callback) {
  var file = fileInput.files.item(0);
  var reader = new FileReader();

  reader.onload = function() {



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

Browser compatibilityUpdate compatibility data on GitHub

Chrome Edge Firefox Internet Explorer Opera Safari
Basic support 7 Yes 3.6 10 11 6
Android webview Chrome for Android Edge Mobile Firefox for Android Opera for Android iOS Safari Samsung Internet
Basic support ? Yes Yes 32 11 6.1 ?

See also

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