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Base64 Encoder/Decoder

The Base64 Encoder/Decoder is a free online tool that converts text to Base64 and decodes Base64 back to readable text. It runs entirely in your browser using the native btoa and atob APIs, so nothing you paste is ever uploaded. No signup and no size limit.

Last updated · Free, no signup

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What is Base64 encoding?

Base64 is a binary-to-text encoding that represents bytes with a 64-character ASCII alphabet. This encoder converts UTF-8 text into standard Base64 and decodes valid Base64 back into readable text, making API values, configuration data, and text-only transport formats easier to inspect or prepare.

Conversion uses TextEncoder and TextDecoder around the browser's native btoa and atob APIs. Base64 is encoding, not encryption or compression, and it increases data size by roughly one third. This decoder expects the standard RFC 4648 alphabet; Base64URL values that use - and _ must be normalized first.