What JSON mistake happens most often?

Trailing commas, single quotes, unquoted keys, and missing brackets are among the most common mistakes.

Why do these mistakes happen?

Because JSON looks similar to JavaScript objects, logs, and config snippets, but has stricter syntax rules.

How can I avoid them?

Validate JSON early, format it for readability, and avoid copying non-JSON syntax into payloads.

Which MyJSONTool pages help most?

JSON Validator, Fix Invalid JSON, and the error guides are the most useful.

HomeBlogCommon JSON Mistakes

Common JSON mistakes

Most broken JSON comes from a small set of mistakes. The faster you can recognize them, the less time you spend fighting request bodies, fixtures, and copied payloads.

Updated June 2026

1. Trailing commas

JavaScript may tolerate them in some contexts, but standard JSON does not.

2. Single quotes

JSON strings and keys require double quotes.

3. Unquoted keys

Object keys like name: "Ada" are valid JavaScript object syntax, not valid JSON.

4. Missing brackets

A truncated payload or manual edit can easily leave an object or array unfinished.

5. Comments

Comments are not part of standard JSON and will break parsers.

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FAQ

Why does JSON look valid when it is not?

Because it often resembles JavaScript objects or config syntax that has looser rules.

What should I check first?

Quotes, commas, comments, and brackets are the best first pass.

Can formatting help me spot problems?

Yes. Once the JSON is valid, formatting makes review much easier.

Where can I get error-specific help?

Use the dedicated error guides under the Errors section.