Why does JSON.parse() throw SyntaxError?

JSON.parse() throws SyntaxError whenever the string it receives is not valid JSON. Common causes: trailing commas, single-quoted strings, undefined or NaN values, HTML mixed into the response, or an incomplete/truncated string.

How do I find what character is causing the JSON.parse error?

The error message includes "position N" (in some engines) or "line X column Y" (in others). Paste the string into FixTools for a clearer human-readable error with the exact location.

My JSON.parse() works in development but fails in production — why?

The data the string contains likely differs between environments. Log and compare the actual string values. Common culprits: different API responses, environment-specific character encoding, null/undefined values, or date format differences.

Can I catch JSON.parse() errors in my code?

Yes: try { const data = JSON.parse(str); } catch (e) { console.error("Invalid JSON:", e.message); }. This prevents an uncaught exception and lets you handle the error gracefully.

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Fix JSON.parse() Errors

You hit a runtime error: SyntaxError: Unexpected token at position N. Your code called JSON.parse() on a string that turned out to be invalid JSON, and now you need to find out exactly what is wrong. Paste the JSON (or the string your code is trying to parse) into FixTools — it will tell you the exact location and type of the syntax error so you can fix it and move on.

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Find the exact cause of your JSON.parse() failure

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See the error line, column, and description

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Fix the JSON and re-validate before deploying

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Paste the JSON string that caused your JSON.parse() error and click Validate to see what went wrong.

How It Works

Step-by-step guide to fix json.parse() errors:

1
Get the JSON string from your code
Log the string your code passes to JSON.parse() — console.log(theString) before the parse call — and copy it.
2
Paste into FixTools
Paste the string into FixTools and click Validate.
3
Read the error location
FixTools reports the line, column, and nature of the error — for example "Unexpected comma at line 5, column 3".
4
Fix the source
Fix the JSON at its source (your API, config file, database, or wherever the string comes from) and validate again.