Decode URL Safe Base64 in JavaScript (browser side)

Question

I am using Gmail's API to get emails from my account. The body of the message is delivered in a "URL safe base64" format. What is the best way to decode this for use? I have found some nodejs solutions, but no client side ones. window.atob does not work since it is URL safe.

Thanks for any help.

score 41 · Answer 1 · edited Oct 07 '21 at 07:34

41

For posterity,

atob(data.replace(/_/g, '/').replace(/-/g, '+'))

As stated by the spec https://www.rfc-editor.org/rfc/rfc4648#section-5 however because this uses atob() it does not support unicode characters and thus requires a polyfill.

edited Oct 07 '21 at 07:34

Community

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answered Jun 13 '17 at 17:53

xori

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Was this meant to be atob(data).replace(/_/g, '/').replace(/-/g, '+') instead – moltenform Mar 22 '18 at 14:20
Reading from the Base64 version of common codec, it should be the inverse:btoa(data) .replace(/\//g, '_').replace(/\+/g, '-'))), – Tcharl Aug 13 '18 at 17:37
jmnben: no we want to replace the '_' and '-' before we do the decoding. – xori Nov 20 '19 at 15:22

score 11 · Answer 2 · answered Jan 22 '15 at 23:46

11

Finally found it. This does URL Safe decoding

https://github.com/dankogai/js-base64

answered Jan 22 '15 at 23:46

wibberding

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Decode URL Safe Base64 in JavaScript (browser side)

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