Free Online JSON Tools — Format, Validate, Convert, Query
Every JSON tool you need, all in your browser. 30 free utilities — format, validate, repair LLM-mangled JSON, convert between JSON / CSV / YAML / XML / TOML / NDJSON / Base64, query with jq and JSONPath (RFC 9535), diff and patch (RFC 6902 + 7396), infer schemas (draft 2020-12), generate TypeScript / Go / Pydantic / Zod. Nothing is uploaded — your data never leaves the tab.
Format, validate, repair
JSON formatter pretty-prints with 2/4/tab indent and optional key sort. Minifier strips whitespace and shows before / after savings. Validator is strict RFC 8259 with plain-English errors and line / column pointers. JSON repair fixes the kinds of breakage LLMs love to produce — trailing commas, single quotes, unquoted keys, smart quotes, JS-style comments. Stringify escapes JSON for embedding in JavaScript, Python, Go, Java, or shell source.
Convert JSON to / from other formats
JSON ↔ CSV with a column picker, nested-flatten strategies, and type inference on the way back.
JSON ↔ YAML with key-order preservation and Norway-problem detection.
JSON ↔ XML with configurable attribute and array handling.
JSON ↔ TOML for pyproject.toml / Cargo / Hugo workflows.
JSON ↔ NDJSON bridges to jsonlkit.com for line-mode work.
JSON ↔ Base64 with standard and URL-safe variants.
Transform JSON → JSON
Sort keys recursively for stable diffs and stable hashes.
Flatten nested objects to user.address.city shape; unflatten back.
Deep merge two or more documents with picky conflict strategies.
Extract all keys or values matching a literal / glob / regex pattern.
Escape / unescape a JSON document into a backslash-encoded string and back.
Query & explore large JSON
jq playground runs full jq in WebAssembly with a 30+ snippet gallery. JSONPath tester supports the modern RFC 9535 dialect alongside legacy Goessner / Jayway. Tree viewer is a collapsible explorer with breadcrumb-path copy. Graph view renders the document as a tree / radial / force layout, exports SVG and PNG.
Diff, patch, merge
JSON diff compares semantically, ignoring key order and whitespace. JSON Patch generates and applies RFC 6902 ops (kubectl-style). Merge Patch handles the simpler RFC 7396 (GitHub-API-style) semantics.
JSON Schema (draft 2020-12 first-class)
Schema generator infers a JSON Schema (draft 2020-12 by default) from one or more sample documents, with format detection.
Schema validator validates with Ajv across drafts 04 / 06 / 07 / 2019-09 / 2020-12.
Schema visualizer diagrams the schema with $ref resolution.
Schema faker generates realistic fake data conforming to the schema.
Schema → types emits TypeScript / Zod / Pydantic / Go / Rust from the schema.
OpenAPI → JSON Schema extracts each component as a stand-alone schema.
Generate typed code from JSON
JSON → TypeScript interfaces / types (plus optional Zod). JSON → Go struct with JSON tags and pointer-for-nullable. JSON → Python Pydantic v2 / dataclass / TypedDict. JSON → Zod with strict / optional handling and inferred TS types alongside.
Inspect
Size analyzer shows raw / minified / gzip / brotli sizes, the heaviest keys, and duplicate strings. Stats profiles the shape — key / value counts, type histogram, max depth, longest key / value.
What they have in common
Everything runs in your browser. The JSON you paste or drop never leaves your machine — there is no server component handling data, no upload step, no account required. See the privacy policy for the longer version.
Modern specs, draft 2020-12 by default. JSON Schema 2020-12, RFC 9535 JSONPath, RFC 6902 / 7396 patches. The older draft-07 / Goessner / Jayway dialects are available as toggles where it matters.
Free to use, with no warranty. Read the terms of use before relying on the output for anything load-bearing. Bug reports and feature requests are always welcome — drop me a line.
— S., [email protected]