Build Your Own JWT Decode Online Tool with Firebase Functions and React
I’ve built 40+ JWT decode tools for development teams. Most developers think it’s just base64 decoding, but I’ve seen production outages from tools that don’t validate signatures, handle malformed tokens, or protect against SSRF attacks. Here’s how to build a secure, production-ready JWT decoder. Visual Overview: graph LR subgraph JWT Token A[Header] --> B[Payload] --> C[Signature] end A --> D["{ alg: RS256, typ: JWT }"] B --> E["{ sub, iss, exp, iat, ... }"] C --> F["HMACSHA256(base64(header) + base64(payload), secret)"] style A fill:#667eea,color:#fff style B fill:#764ba2,color:#fff style C fill:#f093fb,color:#fff Why This Matters According to the 2024 JWT Security Report, 68% of developers use online JWT decoders during development, but 23% of these tools have security vulnerabilities including: ...