Does this verify the signature?
No. It only decodes header and payload so you can inspect claims.
jfmt.dev
JWT Decoder
Paste a JSON Web Token to read header and payload as JSON. Useful for debugging auth, but this page does not verify signatures.
JSON formatter
Input
Output · preview.json
{ }
Run a tool to see a polished result here
Decode vs verify
Decoding only base64-reads the token. Signature verification needs the key and does not happen here — never paste production secrets into any online tool, including this one. Processing stays on this device.
Sample input on this page
The editor is prefilled with a small example for JWT Decoder. The JWT decoder splits header and payload in the browser. It does not verify signatures and never uploads the token. Replace it with your own file; the sample and your payload stay in this tab.
eyJhbGciOiJub25lIn0.eyJzdWIiOiJqZm10IiwibmFtZSI6IkxvY2FsIFRvb2wiLCJpYXQiOjE3MTAwMDAwMDB9.
How to use this tool
- Paste JSON into the JWT Decoder editor. The file stays in this browser tab and is not uploaded to jfmt.dev.
- Click Run. The JWT decoder splits header and payload in the browser. It does not verify signatures and never uploads the token.
- Copy the output, or continue with a related tool below. Related tools on this site include beautify, validate, minify, JSON to CSV, JSON to YAML and JSON to XML — all local.
- JFmt runs in a Web Worker in this tab. Do not paste production secrets if you share your screen.
When this page is the right choice
This dedicated JWT Decoder URL matches that search intent; the homepage stays the general formatter. The JWT decoder splits header and payload in the browser. It does not verify signatures and never uploads the token. Related tools on this site include beautify, validate, minify, JSON to CSV, JSON to YAML and JSON to XML — all local. JFmt runs in a Web Worker in this tab. Do not paste production secrets if you share your screen. Read errors in the output pane instead of sending production payloads to another service.
Related tools
FAQ
Is my token uploaded?
No. Decoding runs in the browser.
What if the token is malformed?
You get an error in the editor. Fix the three base64url segments and try again.
Does this tool upload my file?
No. Parsing and conversion run in a Web Worker in this tab. jfmt.dev does not receive the payload.
Why is there a separate URL from the homepage?
So people searching for this operation land on a page that already selects it. The JWT decoder splits header and payload in the browser. It does not verify signatures and never uploads the token.