API validation tools
These tools check structure you already have: a webhook body, an OpenAPI fragment, a GraphQL query, or a JSON schema instance. Live GET health scores live on Webhook Tester and API Response Analyzer.
Several catalog names (request body, response schema, GraphQL validator) point at the root JSON Schema, JSON, and GraphQL linters — one implementation, not four products. JWT-style names in this category also collapse to JWT Claims Inspector or the Security JWT decoder.
Webhook Tester
Free webhook tester: send payload to URL, get health score (status, latency, response). Test Stripe, GitHub, Shopify. No signup.
/api/webhook-tester
API Response Analyzer
Free API health check: GET request, check status, latency, Content-Type, JSON. Get API health score and recommendations.
/api/api-response-analyzer
Webhook Payload Viewer
Inspect, format, and validate incoming webhook payloads. JSON pretty-print, syntax check. Free webhook debugger.
/api/webhook-payload-viewer
Webhook Capture
Get a unique URL to receive webhooks. See POST/GET requests in real time. Free webhook testing endpoint. No signup.
/api/webhook-capture
Auth Header Validator
Validate JWT, Bearer, and Basic Auth header structure. Check format before sending. Free auth header checker.
/jwt-claims-inspector
JWT Decoder
JWT decoder: paste token, inspect header and payload claims. Free JWT viewer for debugging auth. Base64 decode.
/security/jwt-decoder
OpenAPI Validator
Validate OpenAPI 2.0 / 3.x JSON structure and paths. Check spec before deploy. Free OpenAPI/Swagger validator.
/openapi-snippet-linter
Response Schema Validator
Validate JSON against JSON Schema (draft-07). API response validator. Paste schema and payload. Free online.
/json-schema-validator
GraphQL Query Validator
Validate GraphQL query, mutation, or subscription syntax. Check before sending. Free GraphQL validator.
/graphql-query-linter
Idempotency Key Checker
Validate Idempotency-Key header format (UUID). Check before POST. Free idempotency key validator.
/api/idempotency-key-checker
Request Body Validator
Check if request body is valid JSON before POST/PUT. Validate before sending. Free JSON body checker.
/json-validator-online
API Error Code Analyzer
HTTP error code lookup: status code meaning, suggested action. 4xx, 5xx explained. Free API error guide.
/api/api-error-code-analyzer
Base64 Encoder / Decoder
Base64 encode/decode: text to Base64, Base64 to text. URL-safe supported. Free encoder decoder. No signup.
/base64-encoder-decoder
UUID Generator
Generate UUID v4 for idempotency keys, request IDs, trace IDs. Copy and use. Free UUID generator.
/uuid-generator-validator
JSON Diff
Compare two JSON objects: see added, removed, changed keys. Free JSON diff tool for API responses. No signup.
/api/json-diff
FAQ
- Which tool do I use for a Stripe webhook body?
- Webhook Payload Viewer or Webhook Capture for the bytes; Signature Validator / HMAC for signing. JSON Validator if you only need syntax.
- Is OpenAPI Validator a full spec suite?
- It lints OpenAPI JSON structure and paths. It is not Spectral or a full OAS 3.1 conformance suite.