SyntaxError: Unexpected token ] in JSON at position 0: what it means and how to fix it

What the error means

SyntaxError: Unexpected token ] in JSON at position 0 means the parser expected valid JSON but encountered a character/token that cannot appear there. In practice, it usually means the input is not JSON (or not strict JSON), or it is incomplete.

Most common real-world causes

• There is a stray closing bracket at the start (copy/paste artifact).
• You are parsing a fragment that lost its opening { or [.
• A previous step concatenated JSON incorrectly and left extra closers.

Fast debugging steps

• If the string begins with a closing bracket, remove it or restore missing openers.
• If you expect an array/object, ensure the whole document is present (not truncated).
• Validate locally to pinpoint the next error.

Code example (node)

// Example: stray closing bracket
const bad = ']}\n{"a": 1}';

// Fix: remove the stray prefix or restore missing opening brackets
const ok = '{"a": 1}';
JSON.parse(ok);

Fix without uploading data

If the JSON contains sensitive data, validate and fix it locally. No Upload Tools runs 100% in your browser.

• JSON Validator to pinpoint the exact syntax error.
• JSON Repair to remove comments/trailing commas when the source is not strict.
• JSON Formatter to pretty-print and inspect structure.
• JSON String Escape if the issue is inside a string (newlines/tabs/quotes).

Workflow: validate -> fix the first error -> validate again -> export/convert.

FAQ

Does the exact token matter? Yes. The token often hints at the root cause: < is usually HTML, u is often undefined, and / often points to comments.

Should I just regex-fix JSON? Avoid blind regex edits. Validate after each change so you know what you fixed and what broke.