Troubleshooting Guides

Short, practical explanations for errors developers hit constantly — what causes them, and the fastest way to fix them.

Developer Reference

Need a compact protocol lookup? Browse the HTTP, MIME type, and cron reference guides.

Pillar Guides

• Complete Guide to JSON Errors
• JWT Debugging Guide
• OpenAPI Validation Guide
• JSON Conversion Guide
• API Debugging Toolkit

JSON

• Fixing "Unexpected token" in JSON
• Fixing "Unexpected end of JSON input"
• JSON trailing comma error, explained
• JSON Schema "additionalProperties" errors, explained
• "Bad control character in string literal" error, explained

JWT

• JWT signature verification failed — causes and fixes
• "jwt malformed" / "Not enough segments" error, explained
• JWT "token expired" error, explained
• "JWKS key not found" / kid mismatch, explained
• RS256 vs HS256: which JWT algorithm should you use?

Timestamps & Identifiers

• Unix timestamp: seconds vs milliseconds
• UUID v4 vs v7: which one should you use?
• "Invalid character" / invalid Base64 string, explained

YAML & Regex

• YAML bad indentation error, explained
• "Invalid regular expression" error, explained

API, cURL & OpenAPI

• Fix OpenAPI $ref resolution errors
• Fix converting circular structure to JSON
• Handle OAuth access_denied errors
• Fix webhook endpoint timeouts
• Fix API pagination duplicates and gaps
• Fix HTTP 503 Service Unavailable
• Fix JavaScript Fetch “Failed to fetch”
• Fix cURL SSL certificate errors
• Fix JWT invalid audience errors
• Fix OpenAPI oneOf validation errors
• Fix HTTP 405 Method Not Allowed
• Fix HTTP 409 Conflict
• Fix HTTP 422 validation errors
• Fix OAuth redirect_uri_mismatch errors
• Fix OpenAPI additionalProperties errors
• Fix CORS preflight OPTIONS failures
• Fix OAuth invalid_client errors
• Fix duplicate OpenAPI operationId errors
• Fix cannot deserialize JSON errors
• Handle duplicate webhook events safely
• Fix HTTP 400 Bad Request API errors
• Fix HTTP 404 API endpoint not found errors
• Fix HTTP 502 Bad Gateway
• Fix HTTP 504 Gateway Timeout
• Fix OAuth invalid_grant errors
• Fix CORS Access-Control-Allow-Origin errors
• HTTP 401 vs 403 authentication and permission errors
• Fix HTTP 415 Unsupported Media Type
• Fix HTTP 429 Too Many Requests
• Webhook signature verification failed
• CSV rows with the wrong number of columns, explained
• OpenAPI "missing required field" errors, explained
• Why a cURL command stops working in browser Fetch
• Swagger 2 vs OpenAPI 3: migration differences
• Breaking vs non-breaking API changes
• How to run an OpenAPI diff in GitHub Actions
• OpenAPI change review process
• OpenAPI diff tools compared
• How to generate TypeScript types from OpenAPI
• How to generate nested Go structs from JSON