Base64 to JSON Decoder

Decode a Base64 or base64url string to text and pretty-print it as formatted JSON — perfect for JWT payloads and encoded config. Everything runs in your browser; nothing is uploaded.

How to decode Base64 to JSON

Many tokens and configs store JSON as Base64. This tool Base64-decodes your input to UTF-8 text, then — if the text parses as JSON — pretty-prints it with 2-space indentation. If it isn't JSON, you still get the decoded text, so you can always see exactly what the Base64 contained.

Decoding a JWT payload

A JWT is header.payload.signature; the payload (the middle segment) is base64url-encoded JSON. Paste just that middle segment here to read the claims. Note that this only decodes — it does not verify the signature — and a JWT is not encrypted, so never trust unverified claims. For more on how this works, see Base64 in JWT.

Is this private?

Yes. The decoding happens entirely client-side in JavaScript. Your tokens and payloads are decoded in your browser and are never uploaded — important since JWTs often contain identifiers like user IDs and email addresses. You can confirm this by opening DevTools → Network: decoding fires no request.

Frequently asked questions

How do I decode Base64 to JSON?

Paste your Base64 string into the input above. The tool Base64-decodes it to UTF-8 text, then parses that text as JSON and pretty-prints it with 2-space indentation. If the text is not valid JSON, you still get the raw decoded text.

Can I decode a JWT payload here?

Yes — paste the middle segment of the token (the part between the two dots). It is base64url-encoded JSON and will decode to the claims. The signature is not verified, so treat the result as untrusted.

Does this work with base64url?

Yes. Both standard Base64 and URL-safe base64url are accepted — the -_ characters and missing = padding are handled automatically.

My output isn't valid JSON — why?

The Base64 decoded fine, but the resulting bytes aren't JSON. That's fine — you still get the raw decoded text in the output, so you can see exactly what the Base64 contained.