Base64 Encode & Decode

Convert text to Base64 or turn Base64 back into readable text. Both the standard alphabet and the URL-safe variant are supported, and UTF-8 is handled correctly, so accented characters, emoji and non-Latin scripts survive the round trip intact.

Everything happens in a single request on our server and nothing is retained. That matters here more than for most tools, because Base64 is so often used to wrap tokens, credentials and API payloads.

How it works

Base64 represents binary data using 64 printable ASCII characters. It exists because many systems — email bodies, JSON fields, URLs, HTTP headers, XML documents — were designed for text and will corrupt or reject raw bytes. Encoding to Base64 makes arbitrary data safe to travel through them.

The cost is size: every 3 bytes of input become 4 characters of output, so encoded data is about 33% larger than the original. That is why embedding large images as Base64 data URIs in CSS or HTML often makes a page slower rather than faster, despite saving a request.

Two details cause most of the confusion:

• Padding. The = characters at the end pad the output to a multiple of four. Some systems strip them; decoders usually cope, but strict ones will not.
• URL-safe Base64. Standard Base64 uses + and /, both of which have meaning inside a URL. The URL-safe variant (RFC 4648 §5) substitutes - and _ and usually drops padding. JWTs use this variant, which is why pasting a JWT segment into a standard decoder sometimes fails.

Base64 is not encryption. It is trivially reversible by anyone, offers no confidentiality whatsoever, and should never be used to protect a secret. It is an encoding, in the same category as hexadecimal.

Frequently asked questions