Does it accept base64url (the JWT alphabet)?

Yes — the - and _ alphabet is accepted, and missing padding is added automatically. That's what real JWTs and SAP payloads look like.

What if the input isn't valid Base64?

It says which problem it is — an unexpected character, or the wrong length/padding — rather than returning garbage that looks like a result.

encoders · free tool

Decode Base64 back to text, UTF-8 safe.

Runs in your browser — your data never leaves it

Input

Paste, type, or drop a file. Runs as you type.

Output

Output appears here as you type.

Input

aGVsbG8=

Output

hello

This example is one of Base64 Decode's test cases — if the tool stopped producing this output, the build would fail.

Does it accept base64url (the JWT alphabet)?: Yes — the - and _ alphabet is accepted, and missing padding is added automatically. That's what real JWTs and SAP payloads look like.
What if the input isn't valid Base64?: It says which problem it is — an unexpected character, or the wrong length/padding — rather than returning garbage that looks like a result.

Encode text to Base64 — payloads, certificates, attachments.

Percent-encode text for URLs and query strings.

Decode percent-encoded URL text back to readable form.

Read a JWT's header and claims — it never leaves your browser, and we never verify the signature.