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JSON Validator

Find every syntax error in one pass, catch duplicate keys, and validate against a full JSON Schema. Everything runs in your browser — nothing is ever uploaded.

Validate
Schema Validation
Structure
Paste JSON and click Validate to check it.
📝 JSON Input0 bytes
🩺 Diagnostics
Also try: Full JSON Schema Draft Support ↗ JSONLint ↗

Why this JSON validator is different

Most validators tell you about one problem at a time. This one shows you the whole picture.

🔍

Finds every error at once

A custom parser recovers after each problem and keeps checking, instead of stopping at the first syntax error like most validators.

🪞

Duplicate key warnings

Catches the same key appearing twice in one object — technically legal JSON, but a common source of silent bugs.

📐

Full JSON Schema validation

Check your data against a real JSON Schema: types, required fields, enums, ranges, patterns, and allOf/anyOf/oneOf combinators.

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Exact line & column

Every error and warning points to a precise location, not just a vague character position.

🧬

Auto-inferred structure

Instantly see the shape of unfamiliar JSON as a lightweight schema you can copy and reuse.

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100% client-side

Validation, including schema checks, happens entirely in your browser. Nothing is ever uploaded.

How it compares

A side-by-side look at popular JSON validators.

Feature SEOTriggers jsonlint.com curiousconcept.com jsonschemavalidator.net
Multi-error detection✓First error only✓✗
Duplicate key warnings✓✗✗✗
JSON Schema validation✓ core keywords✗✗✓ full drafts
Auto-infer structure✓✗✗✗
100% client-side✓✓✓✓
Free, no signup✓✓✓✓

Frequently asked questions

Does this tool find every error, or just the first one?▾
It finds every error it can in a single pass. Most JSON validators stop at the first syntax error; this one uses a custom parser that recovers after each problem and keeps checking, so you can fix everything in one round instead of one error at a time.
What is duplicate key detection?▾
JSON technically allows the same key to appear twice in one object, but most parsers silently keep only the last value, which hides bugs. This validator flags duplicate keys as warnings even when the JSON is otherwise syntactically valid.
Can I validate JSON against a JSON Schema?▾
Yes. The Schema Validation tab lets you paste a JSON Schema alongside your data and checks type, required properties, enum values, string/number constraints, array rules, and combinators like allOf, anyOf, and oneOf, listing every violation with its exact path.
Is my JSON data uploaded to a server?▾
No. All validation, including schema validation, runs entirely in your browser using JavaScript. Nothing is sent to SEOTriggers or any third party.
What does the Structure tab show?▾
It infers a lightweight schema from your JSON automatically, showing the type of every field and which keys are present, which is a fast way to document an API response or config file you didn't write yourself.

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