Free Online JSON Tools — Format, Validate, Convert, Generate Types
Every JSON tool you need, all in your browser. 94 free utilities — format, validate, repair LLM-mangled JSON, convert between JSON and CSV / YAML / XML / TOML / SQL / INI / .env, query with jq and JSONPath (RFC 9535), diff and patch (RFC 6902 + 7396), author JSON Schema (draft 2020-12), and generate typed code for TypeScript, Go, Rust, Java, Python, C#, Kotlin, Swift and more. 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. Rust serde structs, Java records or POJOs, C# classes or records, Kotlin data classes, Swift Codable, Dart with fromJson / toJson, and PHP 8 promoted-property classes.
Beyond languages, the same inference drives schema targets: GraphQL SDL with non-null markers, proto3 messages with numbered fields, Avro records with nullable unions, and CREATE TABLE DDL with column types read off the data. Paste an array rather than one record and optional fields are detected for you.
Tabular and config formats
JSON → SQL INSERT writes batched, dialect-correct statements for Postgres, MySQL and SQLite. HTML table and Markdown table handle documentation and tickets; TSV pastes straight into a spreadsheet, and HTML table → JSON scrapes one back out.
For configuration there is INI,
.env with __ nesting,
Java .properties with Unicode escaping, and
URL query strings in bracket, dot, repeat or comma style — each with the reverse direction on its own page.
Relaxed dialects are covered too: JSONC (tsconfig-style comments) and JSON5.
Reshape and clean
Convert key case normalises a whole document to camelCase, snake_case, kebab-case or PascalCase and warns about collisions. Rename keys does bulk renames by list or regex. Remove nulls strips empty values and prunes the containers left behind. Dedupe removes duplicate array elements by value or by key, Filter keeps records matching a readable condition without jq syntax, and Array ↔ object keys, groups or expands a collection.
Standards-level tooling
Canonicalize (RFC 8785) produces the JCS byte-exact form plus a SHA-256 digest — the basis for signing, content addressing and reliable dedupe. JSON Pointer (RFC 6901) resolves pointers with real error messages or lists every pointer in a document, and List all paths enumerates a document in dot, pointer or bracket notation.
On the schema side, Schema diff labels every change breaking or compatible, Migrate draft lifts draft-04 / 06 / 07 to 2020-12 with a change log, Bundle $refs makes a schema self-contained, and Schema → OpenAPI handles the awkward 3.0 dialect differences.
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. JWT decoder reads a token's header and claims with a real expiry check — and never asks for your signing key.
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]