JSON Error Fixes — Parse Errors & Common Mistakes
Diagnose and fix the most common JSON parse errors and mistakes.
Bad Control Character in String Literal in JSON: Cause & Fix
This JSON.parse error means a raw newline, tab, or control character is sitting inside a string. Why it happens, how to escape it correctly, and how to stop it at the source.
415 Unsupported Media Type — Fix JSON API Errors
Fix HTTP 415 Unsupported Media Type errors when sending JSON. Missing Content-Type header, wrong body format, and server-side config fixes for Express, Django, and FastAPI.
CORS Error Fetching JSON from an API — Cause & Fix
Blocked by CORS policy when fetching JSON with fetch() or axios? Here's exactly why, which headers fix it, and how to configure your server.
Converting Circular Structure to JSON — Cause & Fix
TypeError: Converting circular structure to JSON happens when an object references itself. Here's exactly why, and 3 ways to fix it, with code.
Unexpected End of JSON Input — Causes and Fixes
Fix 'Unexpected end of JSON input' in JavaScript. Covers empty responses, truncated API bodies, unfinished JSON strings, and encoding issues with examples.
Unexpected Token in JSON at Position 0 — Causes & Fix
Usually means your fetch got HTML or an empty response instead of JSON. Check the 4 common causes — and the exact fix for each, with code examples.
20 Common JSON Mistakes and How to Avoid Them
From trailing commas to duplicate keys — these are the most frequent JSON errors developers make, with before/after code examples and clear explanations for each.
JSON Parse Errors: How to Fix Every Common Syntax Error
Fix every JSON syntax error fast: trailing comma, single quotes, undefined values, unquoted keys, missing brackets. With before/after examples.