Base64URL Decoder
What is Base64URL Decoder
This decoder turns a Base64URL string back into the original text. Base64URL is the URL-safe form of Base64: it uses - and _ instead of + and / and usually has no = padding. Paste a value, such as a JWT header or payload, and this tool reads it back to plain text in your browser, re-adding padding as needed. If a character does not belong to the alphabet, it flags the string as invalid.
How to use
- Paste the Base64URL string you want to decode.
- Read the decoded text in the output box, updated as you type.
- Copy the result or share the link with the Base64URL filled in.
- To encode text instead, open the Base64URL encoder.
When to use it
Want to read the header or payload of a JWT, or decode a URL-safe token? Paste the Base64URL segment here and see the plain text in one click, no need to add back the = padding yourself. It pairs with the Base64URL encoder, so whatever was encoded comes straight back. If it reports an invalid string, check for + or / characters, which belong to standard Base64, not Base64URL.
Frequently asked questions
Why does it say my string is invalid?
The input has a character outside the Base64URL alphabet, or a length that cannot be valid. Base64URL allows only letters, digits, - and _, so a + or / from standard Base64, or stray symbols, will not decode. Swap + for - and / for _, or fix the stray character, and try again.
Do I need to add the = padding?
No. Base64URL usually ships without padding, and this decoder re-adds it internally based on the length. Input with or without trailing = both decode correctly.
Can it decode a JWT?
It decodes each Base64URL segment. Paste the header or payload part of a JWT (the sections before the signature) to read the JSON. The signature is raw bytes, so it will not show as readable text. Combine parts one at a time.
Does decoding happen on a server?
No. The string is decoded in your browser and never uploaded. Nothing you paste is sent or stored.
Can I share this with my Base64URL pre-filled?
Yes. The URL updates automatically as you type. Copy it from the address bar or use the Copy link button, and anyone who opens it sees your exact input ready to go.
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