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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
HTML Living Standard
WindowBase64 の定義
現行の標準 No change since the latest snapshot, HTML 5.1.
HTML 5.1
WindowBase64 の定義
勧告 Snapshot of HTML Living Standard. No change.
WindowBase64 の定義
勧告 Snapshot of HTML Living Standard. Creation of WindowBase64 (properties where on the target before it).

Browser compatibility

We're converting our compatibility data into a machine-readable JSON format. This compatibility table still uses the old format, because we haven't yet converted the data it contains. Find out how you can help!

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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