JWT Decoder

Decode JSON Web Tokens (JWT) to inspect headers and payloads. Debug authentication issues instantly.

Updated Dec 06, 2025

JWT Token

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Decoded

Security tooling

Decode and validate JWTs without leaking secrets

Paste any JSON Web Token to view its header, payload, and signature details in a safe, client-side environment. The decoder highlights expiration issues, algorithm mismatches, and malformed Base64 segments so you can debug authentication flows quickly.

Inspect every claim

Tokens are split into color-coded sections that mirror the classic header.payload.signature pattern. The header reveals algorithm choices (HS256, RS512, ES256, etc.) while the payload lists registered and custom claims. Human-friendly timestamps convert `exp`, `iat`, and `nbf` values to your local timezone to prevent off-by-one errors.

Use the editor to tweak claim values or regenerate expiration windows before handing tokens to teammates. Because the decoder never transmits data elsewhere, you can safely troubleshoot production incidents on your laptop.

Automatic Base64URL handling
Input strings can include or omit padding; the decoder normalizes both before parsing.
Copy-ready JSON
Copy just the payload or export a formatted JSON object for documentation and QA workflows.

Verify signatures intelligently

Paste an HMAC secret or load a PEM-encoded public key to validate signatures inline. The tool surfaces mismatched algorithms or unsupported hash suites, helping you catch configuration drift between services.

Need to understand how third-party identity providers structure their tokens? Decode samples side-by-side and feed the claims into policy engines or monitoring tools.

Readable diagnostics
Clear banners explain whether the signature matches, the token has expired, or the header references an insecure algorithm.
Key management guidance
Subtle reminders encourage rotating secrets and preferring asymmetric keys when sharing tokens across teams.

When teams use the JWT Decoder

SSO onboarding

Confirm identity provider claims before wiring them into authorization logic.

Mobile debugging

Inspect tokens issued by iOS/Android clients without installing heavy SDKs.

Observability

Document which claims to log so you can trace errors back to authenticated users safely.

Security reviews

Demonstrate how long tokens remain valid and what scope each audience receives.

Next step

Need to re-encode payloads?

Pair this decoder with the Base64 Encoder to rebuild tokens after editing claim bodies or to transport signatures through systems that only support ASCII.

Open Base64 Encoder

Popular combinations

Audit with Diff Checker
Compare JWT Decoder output with previous revisions to avoid regressions.
Share via QR Code Generator
Turn sanitized payloads into QR codes for offline reviews.

Frequently asked questions

What is a JWT?

JSON Web Token (JWT) is an open standard (RFC 7519) that defines a compact and self-contained way for securely transmitting information between parties as a JSON object.

Is it safe to paste my JWT here?

Yes. We decode the token locally in your browser to show its payload. We do not validate the signature against your secret key, and we never send your token to any server.

Can I edit the JWT payload?

You can edit the decoded payload to see how it changes the token structure, but you cannot generate a valid signed token without the original secret key.

How do I know if a JWT is expired?

Look for the 'exp' (expiration) claim in the payload. It contains a Unix timestamp indicating when the token expires. Our tool automatically converts this to a readable date for you.

How to use JWT Decoder

Follow these four quick steps to securely encode or decode payloads right inside your browser—no downloads, no accounts, and no data leaving the FreeTools.run sandbox.

Step 1: Load your source data
Paste text, drag a file, or start with our curated sample to understand how the encoder workflow behaves with real inputs.
Step 2: Adjust tool options
Toggle presets, update formatting rules, or choose export preferences. All controls update in real time so you can preview the effect before committing.
Step 3: Review the live preview
Use the split-pane preview, inline validation, or diff output to confirm the transformation looks correct before you copy anything back into your project.
Step 4: Export or chain another tool
Copy the result, download a file, or jump into a related FreeTools.run utility (like Diff Checker or the QR Code Generator) to continue the workflow without leaving the browser.