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The WindowBase64 helper contains utility methods to convert data to and from base64, a binary-to-text encoding scheme. For example it is used in data URIs.

There is no object of this type, though the context object, either the Window for regular browsing scope, or the WorkerGlobalScope  for workers, implements it.


This helper neither defines nor inherits any properties.


This helper does not inherit any methods.

Decodes a string of data which has been encoded using base-64 encoding.
Creates a base-64 encoded ASCII string from a string of binary data.


Specification Status Comment
WHATWG HTML Living Standard
The definition of 'WindowBase64' in that specification.
Living Standard No change since the latest snapshot, HTML5.1.
The definition of 'WindowBase64' in that specification.
草案 Snapshot of WHATWG HTML Living Standard. No change.
The definition of 'WindowBase64' in that specification.
勧告 Snapshot of WHATWG HTML Living Standard. Creation of WindowBase64 (properties where on the target before it).

Browser compatibility

Feature Firefox (Gecko) Chrome Internet Explorer Opera Safari
Basic support 1.0 (1.7 or earlier) [1] (有) 10.0 (有) (有)
Feature Firefox Mobile (Gecko) Android IE Mobile Opera Mobile Safari Mobile
Basic support 1.0 (1) (有) (有) (有) (有)

[1]  atob() is also available to XPCOM components implemented in JavaScript, even though Window is not the global object in components.

See also


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