How is Base64URL different from standard Base64?

Base64URL (RFC 4648 §5) replaces the + and / characters with - and _, and omits the trailing = padding, so the result is safe to use inside URLs and filenames without escaping.

Why does Base64URL drop the = padding?

The = character has special meaning in URLs and form data, so removing it avoids percent-escaping. The decoder restores the correct padding from the string length when reading the value back.

Can it decode JWT segments?

Yes. JWT header and payload segments are Base64URL-encoded, so you can paste a segment into Decode mode to read its raw JSON.

Will standard Base64 decode here too?

Yes. The decoder converts - to + and _ to / and re-adds padding, so it will also accept ordinary Base64 input.

Is Base64URL encryption?

No. It is an encoding, not encryption — anyone can decode it. It only makes binary data safe to transport as text in URLs; it provides no confidentiality.

Why does decoding fail with an invalid length error?

A Base64URL string must not have a length that leaves a single leftover character after padding is restored. That usually means the value was truncated or an extra character crept in.

Is my data uploaded anywhere?

No. Encoding and decoding happen entirely in your browser using the built-in TextEncoder and atob/btoa functions.

Base64 URL-Safe Encoder

Base64URL encoder and decoder

Base64URL is the URL- and filename-safe variant of Base64 defined in RFC 4648 §5. It swaps the two problematic characters — + becomes - and / becomes _ — and drops the trailing = padding, so the encoded string can travel inside a URL query string, a filename or a JWT without any extra percent-escaping.

How it works

To encode, the tool converts your text to UTF-8 bytes, runs them through the browser’s btoa, then applies three substitutions: + → -, / → _, and it strips trailing =. To decode it reverses those swaps and re-adds the right amount of = padding (so the length becomes a multiple of 4) before calling atob and decoding the bytes as UTF-8.

Example

Encoding Hello, Gera Tools!:

standard Base64: SGVsbG8sIEdlcmEgVG9vbHMh Base64URL: SGVsbG8sIEdlcmEgVG9vbHMh (no + / = here, so identical)

A value containing bytes that map to + or / shows the difference, e.g.:

Standard Base64	Base64URL
`Pz4/Pg==`	`Pz4_Pg`
`+/A=`	`-_A`

Everything runs locally in your browser — your data is never uploaded.