ToolKitSphereJSON Validator & Syntax Linter
Validate JSON syntax and view exact error line, column, and diagnostic tips.
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A single missing comma or unclosed bracket can break an entire JSON payload, and tracking down the exact spot manually is tedious. This JSON validator parses your input and immediately tells you whether it's valid, and if not, exactly which line and column the error is on along with a plain-language explanation of what went wrong. It's built for developers debugging API responses, QA engineers checking test fixtures, and anyone troubleshooting a config file that won't parse. Because the linter runs entirely in your browser, your JSON never leaves your machine, and there's no account or installation required. Paste your JSON below to get instant validation and diagnostics.
Features
- Instant syntax validation as you type or paste
- Precise line and column number for each error
- Plain-English diagnostic messages explaining common mistakes
- Highlights the exact character causing the failure
- Handles deeply nested objects and large arrays
- Distinguishes trailing commas, unquoted keys, and bracket mismatches
- Works with both minified and formatted JSON
- No server round-trip - fully client-side validation
Why use this json validator & linter?
- Finds syntax errors in milliseconds instead of manual scanning
- Keeps sensitive JSON private with browser-only processing
- Gives accurate, actionable error locations, not just pass/fail
- Requires zero setup - just paste and validate
- Free to use with no limits or signup
Frequently asked questions
What makes JSON invalid?
Common causes are trailing commas, unquoted keys, single quotes instead of double quotes, unclosed brackets or braces, and unescaped control characters.
How do I find a JSON syntax error?
Paste the JSON into the validator and it will report the exact line and column number where parsing fails, along with a description of the likely cause.
Is a JSON validator the same as a formatter?
They're related but different: a validator checks correctness and reports errors, while a formatter reformats already-valid JSON for readability. This tool focuses on validation and diagnostics.
Can I validate JSON without an internet connection?
Once the page has loaded, validation runs fully in your browser, so it works even with an unstable connection.
Does this tool support JSON5 or JSONC comments?
It validates strict JSON per the JSON specification; comments and trailing commas are flagged as errors since they aren't valid standard JSON.
Is my data safe when I validate JSON here?
Yes, nothing you paste is uploaded or stored - all validation happens locally in your browser.
Why does my JSON fail even though it looks correct?
Invisible characters, smart quotes from word processors, or a stray comma at the end of an array are frequent hidden causes worth checking.
From the blog
What Is JSON? A Beginner's Explanation
What is JSON? A plain-English explanation of JSON meaning, syntax, and why every API uses it — with a real example and answers to the questions beginners ask.
JSON Escape Characters Explained
JSON escape characters explained: the nine valid escape sequences, escaping quotes and backslashes, \uXXXX and emoji surrogate pairs, and nested JSON strings.
Common JSON Syntax Errors and How to Fix Them
Every common JSON syntax error explained: trailing commas, unquoted keys, single quotes, comments and bad escapes — what each message means and how to fix it.