Web/API/FileReaderSync/readAsText

The readAsText() method of the FileReaderSync interface allows to read File or Blob objects in a synchronous way into an DOMString. This interface is only available in workers as it enables synchronous I/O that could potentially block.

Syntax

readAsText(File);
readAsText(Blob);
readAsText(File, encoding);
readAsText(Blob, encoding);

Parameters

blob: The DOM File or Blob to read.
encoding: The optional parameter specifies encoding to be used (e.g., iso-8859-1 or UTF-8). If not present, the method will apply a detection algorithm for it.

Return value

An DOMString representing the input data.

Exceptions

The following exceptions can be raised by this method:

NotFoundError: is raised when the resource represented by the DOM File or Blob cannot be found, e.g. because it has been erased.
SecurityError: is raised when one of the following problematic situation is detected:

the resource has been modified by a third party; too many read are performed simultaneously; the file pointed by the resource is unsafe for a use from the Web (like it is a system file).

NotReadableError: is raised when the resource cannot be read due to a permission problem, like a concurrent lock.
EncodingError: is raised when the resource is a data URL and exceed the limit length defined by each browser.

Specifications

Specification	Status	Comment
File APIThe definition of 'readAsText' 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
`readAsText`	Chrome Full support Yes	Edge Full support 12	Firefox Full support 8	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 8	Opera Android Full support Yes	Safari iOS Full support Yes	Samsung Internet Android Full support Yes

Legend

Full support: Full support