Why validate first
JSON is strict: one missing comma or quote can prevent a configuration file or API payload from parsing. A browser-side syntax check provides quick feedback without uploading text.
Use the right data types
JSON values include objects, arrays, strings, numbers, booleans, and null. Object keys and strings use double quotes. For example: {"project":"sample","enabled":true,"retries":3}.
Check and format
Open the JSON Formatter & Validator, paste the complete value, and choose Format & validate. If parsing fails, inspect punctuation near the reported location. Remove trailing commas, use double quotes, and use null rather than undefined.
Know what validation proves
A syntax check only proves that the parser can read the document. It does not prove the data matches your application's schema, is authentic, or is safe to execute. Validate application rules separately. The tool runs locally in your current browser tab.