JSON Validator
Check JSON for syntax errors with clear messages.
About JSON Validator
JSON Validator is a free online tool. Check JSON for syntax errors and see a clear message about what is wrong. It runs entirely in your browser, so there is nothing to install, no account to create and no watermark added to your result.
How to use JSON Validator
- Paste your code or data into the input box.
- Choose an option or press the action button.
- Read the result, fix any reported error and copy the output.
Worked example
The text {"a":1,} fails because of the trailing comma. Remove it and the JSON is valid.
Tips for best results
- Common mistakes are trailing commas, single quotes instead of double quotes, and unquoted keys.
- Everything runs in your browser, so you can use JSON Validator even on a slow connection once the page has loaded.
Limits to keep in mind
- The tool works on the text you paste and does not check it against a schema. Always test the output in your own project.
Frequently asked questions
More free developer tools
URL Encoder
Percent-encode URLs for safe transmission.
URL Decoder
Decode percent-encoded URLs back to readable text.
HTML Encoder
Escape HTML special characters into entities.
HTML Decoder
Unescape HTML entities back into characters.
MD5 Hash Generator
Generate MD5 hashes from any text.
SHA-1 Hash Generator
Generate SHA-1 hashes from any text.
Related guides
UUIDs Explained: Versions, Collisions and How to Generate Them
What a UUID is, how version 4 and version 7 differ, why collisions are practically impossible and how to use them as database keys.
2 minBase64 Explained: What It Is, Why It Exists and What It Is Not
How Base64 turns bytes into text, why it adds about a third to the size, where you will meet it and why it is not encryption.
2 minMD5 vs SHA-256: Which Hash Should You Use?
Understand what hash functions do, why MD5 and SHA-1 are considered broken for security and which tool to use for checksums and passwords.