/Web APIs

atob() global function

The atob() function decodes a string of data which has been encoded using Base64 encoding. You can use the btoa() method to encode and transmit data which may otherwise cause communication problems, then transmit it and use the atob() method to decode the data again. For example, you can encode, transmit, and decode control characters such as ASCII values 0 through 31.

For use with Unicode or UTF-8 strings, see the note on "Unicode strings" in the page for btoa().





A binary string (i.e., a string in which each character in the string is treated as a byte of binary data) containing base64-encoded data.

Return value

An ASCII string containing decoded data from encodedData.


InvalidCharacterError DOMException

Thrown if encodedData is not valid base64.


const encodedData = btoa("Hello, world"); // encode a string
const decodedData = atob(encodedData); // decode the string


Browser compatibility

Desktop Mobile
Chrome Edge Firefox Internet Explorer Opera Safari WebView Android Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet
atob 4 12 1 10 10.5 3 ≤37 18 4 11 1 1.0
worker_support 30 12 4 10 17 10 4.4 30 4 18 10 2.0

See also

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