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Unexpected Token in JSON: How to Fix It

This error usually means you are parsing non-JSON content as JSON, or your payload is malformed before parse time. Use this workflow to isolate source and fix quickly.

Fast Diagnosis Checklist

Inspect raw response body before calling JSON.parse or response.json().
Confirm content-type is application/json.
Run payload through JSON Validator.
Reformat payload in JSON Formatter to locate breakpoints.

Common Root Causes

Server returned HTML error page (< token at position 0).
Trailing commas or missing quotes in JSON body.
Double-encoded escaped JSON string not decoded first.
Unexpected BOM or invisible characters at payload start.

Recommended Workflow

Validate syntax first, then compare expected vs actual response shape using JSON Diff. If the source is CSV/XML conversion output, normalize via conversion guides before parsing.

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