JWT & Token Analyzer

Decode JWTs, verify signatures (HS* / RS*), and get practical security checks in one place.

JWT & Token Analyzer
Decode JWTs, verify HS/RS signatures, and review time-based claims.
Settings
Tip: You can paste Bearer <token> or Authorization: Bearer <token>.
For HS* use the shared secret. For RS* paste a PEM-encoded RSA public key.
Result
No analysis yet
Paste a JWT or Authorization header on the left, then click Generate.

About JWT & Token Analyzer

JWT & Token Analyzer – Decode, Validate, and Understand Your Tokens

JSON Web Tokens (JWTs) are everywhere: login sessions, API authentication, single sign-on, mobile apps, and server-to-server integrations. They are small, portable, and easy to transmit, but they can also be confusing to debug. A token might look correct and still fail because of an invalid signature, a clock skew issue, an unexpected audience, or a missing claim. This JWT & Token Analyzer helps you inspect a token quickly and safely so you can identify what is inside, what is wrong, and what should be improved.

How This JWT & Token Analyzer Works

The tool accepts a raw JWT (three dot-separated parts) or a full Authorization header (for example, Bearer <token>). It then decodes the header and payload using Base64URL rules, parses the JSON content, and highlights important fields such as alg, typ, issuer, subject, audience, and time-based claims. If you provide a secret (for HS algorithms) or a public key (for RS algorithms), the tool can also verify the signature and report whether the token is cryptographically valid.

Step-by-Step

  • 1. Paste a token: Add a JWT or an Authorization header that includes a Bearer token.
  • 2. Choose verification: Select Auto, HS*, or RS* and optionally provide a secret/key.
  • 3. Generate analysis: The tool decodes parts, validates structure, and checks common pitfalls.
  • 4. Use the output: Copy formatted tables or raw JSON output into bug reports and tickets.

The analyzer does not modify your token. It only interprets what you provide and computes verification results when you explicitly add a key. This makes it useful for production debugging, test environments, and training.

Key Features

Readable Header and Payload

JWTs compress information into a compact string. This tool expands the header and payload into structured output, making it easy to see algorithms, key identifiers, and claims. You can quickly confirm whether the token uses the expected algorithm and whether claims follow your security policy.

Signature Verification for HS and RS

When you provide an HMAC secret (HS256 / HS384 / HS512) or an RSA public key (RS256 / RS384 / RS512), the tool validates the signature against the token’s signing input. This is critical for confirming whether a token is authentic or has been tampered with in transit.

Expiration and Time Claim Checks

Time-based claims like exp, iat, and nbf are frequent sources of errors. The analyzer converts timestamps into human-readable dates and flags common issues such as expired tokens, tokens not yet valid, or tokens missing a recommended expiration.

Practical Security Hints

Beyond decoding, the tool provides actionable guidance. It can warn you about risky patterns such as alg=none, missing expiration, unusually long validity windows, or mismatches between header algorithm and the verification method you selected.

Use Cases

  • API Debugging: Confirm why a request was rejected (invalid signature, wrong audience, expired token).
  • SSO & OAuth Integrations: Inspect issuer, subject, and audience claims during environment setup.
  • Security Reviews: Check whether tokens always include exp and use approved algorithms.
  • Mobile and SPA Development: Validate that clients receive the correct claims after login.
  • Incident Response: Quickly triage suspicious tokens by inspecting claims and signature status.
  • Education: Learn how JWT parts work and what verification actually checks.

Because JWTs appear across many stacks (Node, PHP, Java, .NET, Go, Python), a universal analyzer saves time and reduces mistakes. Instead of guessing, you can see exactly what the token says and whether it is verifiable with the provided key material.

How to Get the Best Results

Use Realistic Test Tokens

For reliable debugging, test with tokens created by your real issuer (auth server, identity provider, or backend service). If you work with multiple environments, label tokens clearly so you do not mix production and staging secrets.

Verify With the Correct Key Type

HS algorithms require the shared secret used for signing, while RS algorithms require the matching RSA public key. If verification fails, confirm the algorithm in the header and ensure you are using the correct key for that algorithm. The analyzer makes this visible by showing the token’s alg and the verification method you selected.

Watch for Clock Skew

Tokens can fail even when the signature is correct if server clocks disagree. Compare your system time with the token’s iat, nbf, and exp fields. If the token is “not yet valid,” you may need a small leeway in your verifier or correct time synchronization in your infrastructure.

Keep Tokens Short-Lived

Short-lived access tokens reduce risk when a token leaks. If you see extremely long validity windows, consider whether refresh tokens or rotating sessions would be safer. The analyzer can flag tokens with unusually long time-to-expiration.

FAQ

No. The analyzer processes the input for this request and returns a result on the page. Always avoid pasting real production secrets into any third-party environment, and prefer staging keys when possible.

Decoding reads the header and payload, which are not encrypted by default. Verification checks the signature using the correct secret or public key to confirm authenticity and integrity. A token can decode correctly while still being invalid if the signature does not match or the token is expired.

Common causes include an incorrect verification key, mismatched algorithm, missing padding in copied tokens, clock skew affecting nbf or exp, or a token that was re-signed in another environment. Use the header, time checks, and signature result to pinpoint the exact reason.

Yes. If you paste a bearer token that is not a JWT, the tool will report that it is not in JWT format and show basic parsing hints. JWT-specific decoding requires the three-part structure.

Why Choose This Analyzer?

Many token tools only decode the payload, which can create a false sense of security. This analyzer goes further by combining decoding, optional verification, time validation, and practical security hints in a single premium interface. Whether you are debugging an API call, validating an SSO integration, or reviewing security policies, you get a clear, copy-ready report that is easy to share with your team.

Use it whenever you need confidence: understand what is inside a token, confirm whether it is verifiable, and identify the exact reason for failures. This saves hours of guesswork and helps you build safer authentication flows.