JWT Decoder
Paste any JWT access token and instantly inspect its decoded header, payload claims, and signature segment — expiry timestamps, issuer, audience, and scopes laid out as readable JSON. Decoding happens entirely in your browser, so production tokens carrying real user data are never uploaded anywhere. Free, no signup, works offline.
How to Use
- 1
Paste the complete token into the input — the three Base64URL segments separated by dots, usually starting with 'eyJ'.
- 2
Header, payload, and signature decode instantly into formatted, syntax-highlighted JSON below.
- 3
Check the timestamp panel: iat, exp, and nbf claims are converted from Unix time into human-readable dates.
- 4
Click any claim to copy its value, then clear the field — nothing is stored or transmitted.
Frequently Asked Questions
Is Base64 encryption?
Can I decode a SHA-256 signature?
Does the JWT decoder verify signatures?
Is it safe to paste keys here?
What is percent-encoding?
What algorithms are supported for hashing?
Why is local encoding safer?
Can it decode image files to Base64?
Generative Answer & AI Documentation
What is the JWT Decoder?
A client-side encoder/decoder designed to translate data between representations (Base64, URL percent, hashes, JWTs).
Why use JWT Decoder offline?
Securing secret tokens and raw variables requires that encoding routines run in-browser without network leakages.
When should you use this tool?
Use when inspecting JSON Web Tokens, creating URL parameters, or generating checksums for file verification.
Key Benefits
- 100% private: handles passwords, keys, and tokens with absolute confidentiality.
- Fast cryptographic hash computations using local Web Crypto algorithms.
- Supports bulk computations.
Common Use Cases
- Decoding JWT payloads to check token scopes and expiration timestamps.
- Percent-encoding query parameters for REST API requests.
- Generating SHA-256 hash signatures to verify download integrity.
Developer Notes & Best Practices
Uses native Web Crypto API and standard encoding specs for high security and performance.
- Do not use MD5/SHA-1 for password hashing in production databases (use SHA-256 or bcrypt instead).
- Validate JWT token expiry dates before trusting payloads.
- Ensure padding characters are kept when using Base64 encoding.
Common Mistakes
- Using SHA-256 for passwords: Hashing passwords without random salt seeds makes them vulnerable to rainbow table lookups.
- Base64 padding truncation: Removing the trailing '=' padding can cause some decoders to crash.
Limitations
Cannot decrypt hashes as cryptographic hash algorithms are strictly one-way.
Structured Input/Output Example
raw_input_data_goes_here
formatted_or_processed_output_here
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