SprintKit
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100% Client-side & Private Sandbox

JWT Debugger

Security & Auth

Decode JSON Web Tokens, inspect claims, and check expiration status directly in your browser.

Encoded JWT Token
Format: Header.Payload.Signature1 line · 250 chars

Validation & Expiry Status

Token Active & Valid
Expires At:Sat, 02 Feb 2030 05:03:42 GMT
Issued At:Thu, 18 Jan 2018 01:30:22 GMT
Decoded HeaderHS256
Plain Text / Monospace4 lines · 36 chars
Decoded Payload (Claims)CLAIMS
Plain Text / Monospace11 lines · 171 chars
SignatureHS256
sample_signature_not_verified_here
Guide & Documentation

Secure, In-Browser JWT Token Decoder & Claim Inspector

Decode JSON Web Tokens (JWT) without sending sensitive tokens to remote servers. Inspect headers, payload claims, expiration timestamps (exp, nbf, iat), and signature status locally and privately.

How to Decode a JWT in SprintKit

01

Paste JWT String

Paste your Bearer token or raw encoded string (header.payload.signature) into the input area.

02

Inspect Decoded Parts

View color-coded JSON representations of the Header (algorithm, type) and Payload claims (sub, iss, aud, roles).

03

Check Expiration & Timestamps

Check human-readable dates for exp (Expiration), iat (Issued At), and nbf (Not Before), with live expired / active indicators.

Why Use SprintKit JWT Debugger

Zero Token Leakage

Many public JWT tools transmit your auth tokens to backend servers. SprintKit executes 100% locally in your browser sandbox.

Automatic Epoch Time Conversion

Converts Unix timestamps into human-readable local and UTC dates with countdown timers until token expiration.

Header & Claims Breakdown

Instantly identifies token algorithm (RS256, HS256, ES256) and flags malformed or expired signatures.

Copy Decoded JSON

One-click copy of decoded payload claims for mocking, unit testing, or API development.

JWT Security Best Practices

  • §1Never put sensitive passwords, credit cards, or confidential PII inside JWT payloads — JWTs are signed, not encrypted (unless using JWE).
  • §2Keep access token lifespans short (5 to 15 minutes) and pair them with rotating refresh tokens stored in HttpOnly cookies.
  • §3Always verify the algorithm header (alg) on the server to protect against 'alg: none' spoofing attacks.

Frequently Asked Questions

Is this JWT decoder safe for production tokens?
Yes. The decoding logic runs entirely inside your client browser using native JavaScript Base64URL decoding. No tokens are sent over the network.
What JWT algorithms are supported?
SprintKit decodes all standard RFC 7519 JWT tokens, including HS256, HS384, HS512, RS256, RS384, RS512, and ES256.
Can I verify the cryptographic signature?
Yes, by providing your HMAC secret or public RSA key, the tool verifies the cryptographic hash in real-time.

Related Agile & Developer Tools

JSON Formatter

Format, validate, and inspect JSON payloads.

Base64 Encoder

Encode and decode standard and URL-safe Base64 strings.

Timestamp Converter

Convert Unix epoch seconds/millis to human-readable dates.