# fastapi.online JWT Decode

> fastapi.online JWT Decode is a paid API for AI agents from api.fastapi.online, paid per call via x402, $0.0005/call, status unknown (last checked 2026-09-14).

Decodes a JWT token and returns its header, payload, and signature components without verification

## Facts

- Endpoint: POST https://api.fastapi.online/jwt-decode
- Price: $0.0005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/fastapi-online-jwt-decode-25a66e67
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_ap0qVBtLDok3NYyIDiecK

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability fastapi-online-jwt-decode-25a66e67 -d '<json body>'
```

Example prompt: Can you decode this JWT token for me and show me what's in the payload: eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ.SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c

## When to prefer this

Use this endpoint when you need to quickly inspect or debug the contents of a JWT token without needing cryptographic signature verification. It is ideal for development and debugging workflows where you want to read claims, check expiry, or audit token structure. Prefer this over manual base64 decoding for convenience in agent pipelines.

## Known failure modes

- Malformed or non-JWT string returns a parsing error
- Token exceeding 8000 characters is rejected
- Empty token string is rejected by input validation
- Network or payment failure (402) if USDC payment is not provided
- Signature is NOT verified — this endpoint only decodes, does not authenticate

## How this service works

Chat, embeddings, OCR, speech-to-text, image editing, image understanding (captioning/Q&amp;A), text-to-speech, translation, writing tools, classification tools, developer tools, local utilities, format/checksum validators, encoding &amp; crypto utilities, date/time calculators, geo/coordinate math, math &amp; finance calculators, novelty tools, and business/social writing generators — 179 endpoints in all, across multiple specialized self-hosted models. Pay per call with crypto — no signup — or get an API key.

## Output

Returns the decoded JWT broken into its three components: the header object (containing algorithm and token type), the payload object (containing all claims such as sub, iat, exp, roles, and any custom claims), and the signature string — all without performing cryptographic signature verification.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "token": {
   "type": "string",
   "maxLength": 8000,
   "minLength": 1
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/fastapi-online-jwt-decode-25a66e67/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.fastapi.online](https://www.zero.xyz/host/api.fastapi.online/llms.txt)