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JWT & OAuth Token Debugger

Zero Egress

Decode, inspect, verify Web Crypto signatures, and test tokens client-side. Zero server transmission guaranteed.

Sample Tokens:

Encoded Token

HEADER.PAYLOAD.SIGNATURE

eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiJ1c3JfOTA5MmExZmIiLCJuYW1lIjoiQWxleCBSaXZlcmEiLCJlbWFpbCI6ImFsZXhAcHJpdmF0b29scy5kZXYiLCJyb2xlcyI6WyJhZG1pbiIsImRldmVsb3BlciJdLCJzY29wZSI6InJlYWQ6YWxsIHdyaXRlOmFsbCIsImlzcyI6Imh0dHBzOi8vYXV0aC5wcml2YXRvb2xzLmRldiIsImF1ZCI6ImFwaS5wcml2YXRvb2xzLmRldiIsImlhdCI6MTc4OTA2MjAxOCwiZXhwIjoxNzkxNjU3NjE4LCJqdGkiOiJjZjU0OWExMi05MGMwLTQxZDAtYWM5Ny1mOWEwMmZhZTcxYjIifQ.5a1KJ1PrPav0iKn5iiqhLnswz1NdyM5khnlyYlflMLQ

Architectural Privacy Guarantee

Cryptographic JSON Web Token Debugger with Client-Side Verification

Decode, edit, and cryptographically verify JSON Web Tokens (JWT) using the native browser Web Crypto API. Inspect headers, claims, expiration timestamps, and HMAC/RSA signatures without sharing secrets or tokens with third parties.

In-Browser Technology:Web Crypto API (SubtleCrypto)Base64URL Buffer StreamingReactive State StoreLive Expiration Monitor

How Client-Side Processing Works

Every step executes within your browser runtime without network calls or cloud storage.

1The JWT string is split into header, payload, and signature components and decoded via Base64URL decoders.
2Standard claims (exp, nbf, iat, iss, aud, sub) are parsed and formatted into human-readable timestamps and countdowns.
3For HMAC tokens (HS256/384/512), Web Crypto imports your secret key into a secure crypto key context and validates the SHA signature locally.
4For asymmetric tokens (RS256), public PEM keys can be imported for local mathematical signature verification.

Common Workflows & Use Cases

Confidential Authentication Token Debugging

Inspect OAuth 2.0, OpenID Connect, and internal microservice session tokens without leaking enterprise user credentials to public websites.

Token Expiration & Clock Skew Audits

Analyze token TTL, issued-at timestamps, and clock skew issues when debugging token refresh loops.

Claim Modification & Mocking

Edit payload claims in real time and re-sign tokens with local test secrets for frontend unit testing and API mocking.

Signature Algorithm Verification

Confirm tokens are correctly signed with expected cryptographic algorithms and not vulnerable to 'none' algorithm exploits.

Questions & Answers

Frequently Asked Questions

Why should I use this instead of jwt.io?

Public web token debuggers transmit tokens over the network, where browser extensions, proxies, or servers can intercept sensitive user identities or session credentials. Privatools operates strictly client-side with zero data uploads.

Are my secret keys or tokens logged anywhere?

No. All signature validations execute in browser memory via window.crypto.subtle. No analytics or server logs exist.

Which cryptographic algorithms are supported for verification?

It supports HS256, HS384, HS512, and RS256 using standard Web Crypto primitives.