Does 'Invalid JSON' always mean my syntax is wrong?
Usually, but a bare 0, false, "", or null value is a known exception — those are valid JSON but report as invalid here due to how the check works.
Developer Tools
Validate JSON Syntax
Check whether pasted text is valid JSON, right in your browser.
How the validity check actually works
This validator runs your pasted text through JSON.parse and reports "Valid JSON" or "Invalid JSON" based on whether that parsed result is truthy. That distinction matters for one specific edge case: a handful of syntactically valid JSON values — the number 0, the boolean false, an empty string "", and null — all parse successfully but are themselves falsy values in JavaScript, so this checker currently reports them as "Invalid JSON" even though they're perfectly valid.
For typical JSON objects and arrays (the vast majority of what gets pasted here), this distinction never comes up, since a non-empty object or array is always truthy. It only matters if you're specifically checking a bare top-level primitive like `0`, `false`, `""`, or `null`.
Workflow at a glance
Use this quick flow to understand where the tool fits in your work and what to review before relying on the output.
Review checklist
Before
Know that this check is based on truthiness, so a bare 0, false, "", or null value is a known edge case that reports as invalid.
After
For anything reported invalid, check for missing quotes, trailing commas, or unclosed brackets as the most common causes.
When a quick validity check is enough
Use it for a fast yes/no check on whether a JSON object or array payload is syntactically valid, before pasting it into code, a config file, or a request body.
Who validates JSON like this
Developers debugging a payload
Quickly confirm whether an API response or request body is syntactically valid JSON.
Support engineers
Check whether a customer-reported payload is valid before assuming it's a code bug.
Students learning JSON syntax
Get instant feedback on whether a practice example is correctly formatted.
QA testers
Confirm a test fixture's JSON is valid before using it in a test case.
What this checker does
Instant valid/invalid result
Reports the check result as soon as you paste text, no button needed.
Uses native JSON.parse
Relies on the browser's built-in JSON parser for the actual syntax check.
Works for objects and arrays reliably
The common case — a top-level object or array — is checked accurately.
Runs entirely client-side
Nothing you paste is sent to a server.
Validating JSON step by step
- 1Paste the JSON you want to check into the input box.
- 2Read the Valid JSON or Invalid JSON result below it.
- 3If it's invalid, check for the usual culprits: missing quotes, trailing commas, or unclosed brackets.
- 4Use JSON Formatter afterward if you also want to see the structure clearly.
Where a quick check helps
Quickly confirming whether an API response or request body is syntactically valid JSON.
Checking whether a customer-reported payload is valid before assuming it's a code bug.
Getting instant feedback on whether a practice JSON example is correctly formatted.
Confirming a test fixture's JSON is valid before using it in a test case.
Where your JSON goes
The check runs using your browser's native JSON.parse — nothing you paste is sent to a server.
Reading the result correctly
- For typical objects and arrays, trust the result directly — the falsy-value edge case only affects bare primitives.
- If you're specifically checking a bare value like 0, false, or null and get "Invalid," know that this is a quirk of this checker, not necessarily your JSON.
- Use JSON Formatter alongside this if you also want to see the structure, not just a valid/invalid result.
- Check for trailing commas and unquoted keys first if you get an unexpected invalid result on an object or array.
Validator mistakes to avoid
Testing a bare falsy value
Valid JSON like 0, false, "", or null currently reports as "Invalid JSON" here, since the check is based on truthiness rather than parse success alone.
Assuming this validates business logic
It checks syntax only — not whether required fields exist or values are the right type.
Not checking for trailing commas
A trailing comma after the last item is a common cause of unexpectedly invalid JSON.
Skipping the formatter step
For anything beyond a simple yes/no check, JSON Formatter will show you exactly where a structural problem lives.
When you need more than a validity check
JSON Validator gives a fast, reliable yes/no check for typical JSON objects and arrays. For a bare primitive value, or when you need to actually see the structure, use JSON Formatter instead.
Need hands-on help?
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FAQ
JSON Validator FAQ
Answers for using JSON Validator on I Love Tool XYZ.
Does it validate my data's structure or types?
No, only syntax — it doesn't check whether required fields exist or values are the right type.
Is my JSON sent to a server?
No, the check runs using your browser's native JSON.parse.
How is this different from JSON Formatter?
This gives a valid/invalid result only; JSON Formatter also shows you the indented structure.