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Validate JSON

Paste a document, get the exact lines where it breaks, then walk the tree — strict JSON or JSONC, nothing uploaded.
Strict JSONJSONCInsert sampleInsert broken sampleClear

Strict mode: no comments, no trailing commas (RFC 8259)

Paste JSON to see diagnostics, the tree, and line-level stats.
Nothing in yet

Paste, drop, or type to begin. Everything stays on this device.

Next door in JSON

- JSON formatter (/json/formatter)
- JSON Query (/json/query)
- JWT decoder (/web/jwt)
All JSON tools (/json)

Canonical HTML: https://nutter.tools/json/validator
Markdown version: https://nutter.tools/json/validator/index.md
Plain-text version: https://nutter.tools/json/validator/index.txt
Agent index: https://nutter.tools/llms.txt