Which JSON Schema drafts are supported?

Draft 2020-12 (default), 2019-09 and draft-07 natively. Draft-04 and draft-06 schemas are accepted with their boolean exclusiveMinimum / exclusiveMaximum and id forms upgraded automatically, which covers the vast majority of older schemas.

What counts as invalid JSON?

Trailing commas, single quotes, unquoted keys, comments, and undefined are all invalid per RFC 8259 and will be flagged, each with the exact position of the first error.

Why does my valid-looking JSON fail?

Most failures come from copy-paste artifacts: smart quotes, zero-width characters, or BOM markers. The hints panel names the likely cause and the Fix issues button removes them.

What is a duplicate key warning?

JSON allows the same key twice in an object, but every parser silently keeps only the last value. The validator lists each duplicate with its line so you can decide which one you meant.

What is a precision-loss warning?

Integers beyond ±2^53 (about 9 quadrillion) and decimals with more than 15 significant digits cannot be represented exactly by JavaScript and most JSON consumers. Send such IDs and amounts as strings.

JSON Validator

Check whether your JSON is syntactically valid and, optionally, whether it conforms to a JSON Schema (drafts 2020-12, 2019-09 and draft-07 via ajv). Errors are reported with line and column numbers, schema violations list the offending path and jump to its line, and the tool also flags duplicate keys, numbers that lose precision in JavaScript, and common copy-paste damage. NDJSON mode validates each line separately.

Runs locally in your browser

For large JSON, open fullscreen to inspect it comfortably

Validate against a JSON Schema

Paste JSON below to validate it.

JSON to validate

0 chars · 1 line

JSON Formatter

Beautify, minify, sort, query and repair JSON with a tree view and copy-as code export.

JSON Minifier

Minify JSON, strip nulls, measure gzip size and encode as Base64 or URL-safe text.

JSON Path Finder

Explore JSON as a tree, click any value to copy its path in 7 syntaxes, and evaluate JSONPath or jq queries.

JSON Diff

Compare two JSON documents side by side, ignore keys, match arrays by id and export JSON Patch or Merge Patch.

How to use JSON Validator

1Paste or upload the JSON to check. The status banner turns green when it parses.
2Read the likely-cause hints (smart quotes, comments, trailing commas…) and click one to jump to its line, or press Fix issues to repair automatically.
3Turn on Validate against a JSON Schema, paste or generate a schema, and pick the draft. Violations list the path, keyword and line.
4Switch to NDJSON / JSON Lines to validate a log or export line by line, with a per-line results table.

About JSON Validator

JSON Validator is part of FizzKit — a collection of focused developer and ad-tech tools. Because everything runs locally, it works offline once loaded and never exposes your data to a remote server.

Frequently asked questions

Yes. Enable the JSON Schema pane, paste a schema (or generate one from your sample) and choose the draft. Validation uses ajv, the same library most Node.js APIs use, so results match production behaviour. Each violation shows its instance path, keyword and the line in your document.

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