JSON Validator

1. Validate syntax — Paste your JSON and click "Validate JSON." The tool checks for syntax errors, shows precise line/column locations, and optionally auto-repairs common issues like trailing commas, single quotes, and unquoted keys.
2. Validate against a schema — Switch to Schema mode, paste your JSON data on the left and a JSON Schema on the right. Click "Validate Against Schema" to check types, required fields, patterns, and constraints. Use "Generate Schema" to auto-create a schema from sample data.
3. Compare two JSON documents — Switch to Compare mode, paste your two JSON documents side by side, and click "Compare." The semantic diff engine shows additions, removals, and changes with exact JSONPath locations — ignoring key order differences.

JSON (JavaScript Object Notation) has become the universal data interchange format for modern web development. APIs return it, configuration files rely on it, databases store it, and front-end applications consume it everywhere. But JSON is notoriously strict about its syntax — a single trailing comma, an unquoted key, or a misplaced bracket can silently break an entire application. That is where a reliable JSON validator becomes essential.

Syntax errors in JSON can cause cascading failures across your stack. A malformed API response will crash your front-end parser. A broken package.json will prevent npm install from running. An invalid configuration file will cause your server to fail at startup with a cryptic error message. Our JSON validator catches these issues instantly, pinpointing the exact line number, column number, and nature of every error — so you can fix problems in seconds instead of debugging for hours.

Beyond basic syntax checking, JSON Schema validation is critical for maintaining data integrity in production systems. A JSON Schema defines the expected structure, data types, required fields, value constraints, and relationships within your data. When you validate incoming API payloads against a schema, you catch malformed requests before they reach your business logic. When you validate outgoing responses, you guarantee contract compliance with your API consumers. Our Schema mode supports type checking, required fields, string patterns, numeric ranges, enum values, array constraints, and deeply nested object validation.

The JSON diff and compare capability solves another common pain point. When debugging API responses, comparing config files between environments, or reviewing data changes in pull requests, you need a semantic comparison — not a line-by-line text diff. Our compare engine performs a deep structural comparison that understands JSON semantics: two objects with the same keys in different order are treated as identical. Differences are categorized as additions, removals, or value changes, each with the exact JSONPath so you know precisely where and what changed.

What makes this tool unique is that it combines all three capabilities — syntax validation, schema validation, and structural comparison — in a single, fast, browser-based interface. Most online JSON validators only check syntax. Most schema validators are separate tools. Most diff tools are general-purpose text comparers that do not understand JSON structure. Here, you get all three in one place, with auto-repair options that can fix trailing commas, single quotes, unquoted keys, and JSONC comments automatically.

Privacy first: all processing happens 100% in your browser using client-side JavaScript. Your JSON data is never uploaded to any server, never logged, and never stored anywhere. This makes it safe to validate sensitive data — API keys, user records, financial payloads — without any privacy risk. Need to format or beautify your JSON after validating it? Use our JSON Formatter tool to pretty-print with syntax highlighting and tree view.

The tool works with any JSON — API responses, package.json, tsconfig.json, GeoJSON, JSON-LD structured data, Firebase rules, AWS CloudFormation templates, Docker Compose overrides, and any other JSON-based configuration or data format you work with.