JWT Tool – Token Decoder

Fish Network

About this app

JWT Tool — The Complete JWT Toolkit

A fast, privacy-first JWT toolkit for developers, security professionals, and learners.
Decode, build, and verify JSON Web Tokens — completely offline.

JWT Decoder
• Paste JWT or extract from clipboard instantly
• View decoded header, payload, and signature
• Real-time expiration countdown timer
• Verify signatures (HS256, RS256, ES256 and more)
• Automatic security vulnerability scanning
• Load example tokens to learn JWT structure

JWT Builder
• Create tokens with customizable claims
• Quick templates: Auth, ID, Refresh tokens
• Support for multiple algorithms (HMAC, RSA, ECDSA)
• Set expiration with quick buttons (+1h, +1d, +7d)
• Random secret key generator with strength indicator
• Real-time token preview with color-coded sections

JWT Learning Guide
• Structured tutorials from beginner to advanced
• Learn JWT basics, structure, and algorithms
• Interactive practice exercises
• Track your learning progress

Developer Tools
• Base64 Encoder/Decoder
• Unix Timestamp Converter
• Cryptographic Key Generator

Security Features
• Detect alg=none vulnerability
• Identify weak secrets and key confusion attacks
• Check missing expiration and required claims

Token History
• Save decoded and generated tokens
• Mark favorites for quick access
• Organize by date

Privacy First
• No account required
• No tracking or analytics
• Works fully offline
• All data stays on your device

Whether you're debugging authentication flows, building secure APIs, or learning JWT concepts, JWT Tool is your essential mobile companion.

What’s new

1.0