json0 vs JSONLint

Short answer: for checking whether JSON is valid, both work and both process your JSON in the browser. Use JSONLint when a document has many errors and you want them all listed at once, or a tool to repair it. Use json0 when you want a page that loads no ads, analytics or trackers, or when validating is one step in a longer job (diffing, querying, turning it into a table or a schema).

JSONLint is one of the oldest JSON validators on the web and still one of the most used. json0 is newer and broader. Here is how they compare on the things that matter when you paste a payload from work.

At a glance

Where your data goes

Both tools say the same thing about the JSON itself: it is checked in your browser and not sent anywhere. JSONLint's privacy policy states that your JSON "is never sent to our servers for processing" and that there is "no server-side logging of your JSON content". json0 has no server that could receive it.

The difference is everything around the JSON. JSONLint is funded by advertising: its policy lists Google Analytics, analytics cookies and advertising cookies from BuySellAds. When we loaded jsonlint.com once in headless Chrome on 25 October 2026, the page contacted 47 other hosts, most of them ad exchanges and bidding services, before anything was pasted. The same test on json0.dev contacted none: the page, its script and its fonts all come from json0.dev.

None of those requests carried pasted JSON in our test. But if your company's policy is "no third-party scripts on pages where we handle customer data", json0 is the one that passes it. Its privacy page lists every request the site can make and shows how to check them in your browser's network panel.

The error messages

Take a webhook payload with a missing comma:

{
  "id": "evt_3Nf81",
  "type": "invoice.paid",
  "data": {
    "invoice": "in_7Hc2",
    "amount_paid": 2900,
    "currency": "eur"
    "customer": "cus_R2d9"
  }
}

json0 says Not valid JSON. Line 7, column 22: Expected "," or "}" after this value, found a quote. It points at the end of "currency": "eur", exactly where the comma is missing, highlights that line in the editor and shows the lines around it.

JSONLint reports the error with its line number too. Its strength is the case with several problems: it lists every error and warning in one pass, where json0 stops at the first and you fix them one at a time.

Where JSONLint is stronger

• Many errors at once. A hand-edited config with five mistakes is quicker to fix when you see all five.
• Repair. Its Repair tool tries to fix common mistakes such as trailing commas and single quotes for you.
• Loading from a URL. jsonlint.com/?url=… fetches and validates a public JSON file, which is handy in documentation and bug reports.
• Converters. JSON to Excel, SQL, XML, Java or Python, and the other direction for some.
• Extension and app. A Chrome extension and a Mac app, if you validate all day.

Where json0 is stronger

• No ads, analytics, cookies or third-party requests. Nothing on the page talks to anyone but json0.dev.
• Readable errors. Line and column, a reason in plain words, and the broken lines shown in place.
• The next step is on the same site. After the document is valid you can format it, compare it with another version, query it, turn it into a table, infer a schema and types, or redact it before sharing, without pasting it into another site.
• MongoDB and CSV tools that JSONLint does not have: Extended JSON, ObjectId, a query tester, a CSV viewer and CSV diff.

Which to use

• A document with many errors, or one you want fixed for you: JSONLint.
• Validating at work, where the page must not load third-party scripts: json0.
• Validating as part of debugging, before a diff, a query or a conversion: json0, so the document stays in one place.

Frequently asked

Is it safe to paste JSON into JSONLint? Its privacy policy says your JSON is processed in your browser and never sent to its servers. The page does load advertising and analytics scripts, so check your organisation's rules about third-party scripts.

Does json0 accept comments or trailing commas? The validator checks strict JSON, as defined by RFC 8259, and reports comments and trailing commas as errors, because most parsers reject them. The Extended JSON tool reads relaxed syntax with comments, single quotes and unquoted keys, and writes it back as strict JSON.

Can json0 validate against a JSON Schema? Yes: Schema and types infers a schema from samples and its Validate a document tab checks another document against it.