SyntaxError: Unexpected token o in JSON at position 1: what it means and how to fix it

What the error means

SyntaxError: Unexpected token o in JSON at position 1 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

• You passed an object into JSON.parse (it becomes the string [object Object]).
• You are parsing something that is already parsed (double-parse).
• You are parsing a non-JSON response like ok/ok\n/object.
• A logger/debugger prepended text before the JSON payload.
• A client library returned an object, but you treated it as JSON text.

Fast debugging steps

• Check typeof: the value should be a string before parsing.
• If it is an object, remove JSON.parse (or stringify before storing).
• If it is [object Object], trace where implicit string conversion happens.

Code example (node)

// Classic reason for "Unexpected token o" at position 1:
JSON.parse({});
// coerces to "[object Object]" -> token "o" at position 1

// Fix: only parse strings
if (typeof value === 'string') JSON.parse(value);
else value;

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.