JSONKit

The last JSON tool you will ever need.

Format, validate, convert and diff JSON. Instant, accurate and 100% private — every byte stays in your browser, never on a server.

Open Formatter →Compare two JSONs

✓No upload · No data sent · Works offline after first visit

Live JSON formatter — validate, inspect & explore.

Paste any JSON or pick a real-world sample. Instantly get syntax highlighting, type distribution, structure shape, and click any line to copy its JSONPath. Zero uploads — runs entirely in your browser.

Try:
Input✓ Valid
9 lines · 181 B
Formatted output
1{
2 "login": "torvalds",
3 "name": "Linus Torvalds",
4 "public_repos": 6,
5 "followers": 236000,
6 "company": "Linux Foundation",
7 "location": "Portland, OR",
8 "hireable": false
9}
Shape
.{ 7 }
●login"torvalds"
●name"Linus Torvalds"
●public_repos6
+ 4 more
Value types
4 str2 num1 bool1 obj
Metrics
Size
181 B
Keys
7
Depth
1
Lines
9
↓Minified: 152 B · saves 16%
TIPHover any output line to see its JSONPath. Click to copy it to your clipboard.

Your complete JSON toolkit

Format, validate, diff, convert formats, generate typed code, and more — 83+ tools, all free, all browser-side, zero uploads.

Formatters & Preview

12

AI Tools

7
✦ New

AI JSON Assistant

Fix, explain, convert & generate JSON, schema, mock data, queries and regex with AI.

Fix & convertSchemaMock data
✦ New

AI Regex Generator & Explainer

Generate a regex from plain English, or paste a regex to have it explained.

GenerateExplainAny pattern
✦ New

AI SQL Generator

Turn a plain-English request into SQL for Postgres, MySQL, SQLite or SQL Server.

Text to SQL4 dialectsJoins & aggregates
✦ New

AI Mock Data Generator

Generate a realistic JSON array of test data from a description.

Realistic dataPick countJSON array
✦ New

AI Cron Generator

Convert a plain-English schedule into a cron expression with an explanation.

Text to cron5-fieldExplained
✦ New

AI JSON Query Generator

Describe what to extract in plain English — get a jq filter and JSONPath expression.

jq + JSONPathReads your JSONExplained
✦ New · AI & LLM

JSON examples for AI & LLM engineering

Copy-ready request & response shapes for OpenAI, Anthropic Claude, embeddings, RAG, agents, function calling, MCP and more — every field documented, one click to open in a tool.

OpenAI Chat Completion Response

OpenAI Chat Completions API response with choices, message, finish_reason, and usage.

View example

Anthropic Claude Messages Response

Claude Messages API response with content blocks, stop_reason, and token usage.

View example

LLM Tool / Function Call

Function-calling JSON: a tool definition plus the model's tool_call with arguments.

View example

Embedding Vector Response

Embeddings API response with the vector array, model, and usage.

View example

RAG Document Chunk

A RAG chunk with text, source metadata, embedding reference, and relevance score.

View example

Chat Conversation History

Ordered messages array with system, user, and assistant roles for LLM chats.

View example

AI Agent Run Trace

Agent run with goal, reasoning steps, tool calls, observations, and final output.

View example

MCP Message (Model Context Protocol)

Model Context Protocol (MCP) JSON-RPC 2.0 message: tools/list and tools/call.

View example
Browser extension

Take JSONKit into your browser

Auto-formats any JSON API response into a tree, diffs two documents, decodes JWTs, and captures network JSON in DevTools — free, no account.

Get the free extension →

✓ Live on the Chrome Web Store

  • Auto-formats any JSON API response into a tree
  • Local JSON diff & instant JWT decode
  • 100% private — zero network requests

What engineers say about JSONKit

Developers share how JSONKit fits into their daily workflow — formatting, diffing, validating, and converting data.

“JSONKit is the only online tool I trust with production API payloads. Nothing is uploaded — I paste real tokens and keys without sanitising first. The formatter is instant, no spinner, no lag.”

AM
Alex M.
Senior Backend Engineer

“The JSON Diff view saves me 20 minutes every sprint. I paste before-and-after payloads from two API versions and see exactly what changed. Nothing else shows diffs this cleanly.”

PK
Priya K.
Full-Stack Developer

“I keep JSONKit pinned in every browser. Offline support hooked me — I work on trains and most JSON tools break without a connection. The JWT decoder with human-readable expiry is chef's kiss.”

MR
Marcus R.
DevOps Engineer

“Switched from jsonformatter.org the day I found the schema validator here. It shows the exact path to the error — not just 'invalid JSON'. Saves me real debugging time every single day.”

SL
Sarah L.
API Developer

“JSONKit's CSV-to-JSON handles our edge cases — embedded commas, unicode, mixed types — without breaking. We use it as part of our data pipeline QA process now. Solid tool.”

DW
Daniel W.
Data Engineer

“As a solo dev I can't afford to leak client data. JSONKit being fully client-side is a hard requirement, not a nice-to-have. Bonus: the TypeScript interface generator is brilliant.”

TH
Tom H.
Freelance Developer

“The JSONPath tester is the best I've used. Live results as you type, all matching nodes at once. Saved me hours of trial-and-error querying deeply nested API responses.”

EC
Emma C.
Frontend Engineer

“No account sign-up, no cookie banners, no upsells. It just works. Been using JSONKit for months and it's become my most-visited tool. The minifier alone pays for itself in bandwidth.”

RK
Ryan K.
Backend Developer

“Our whole team uses JSONKit. The Schema Validator caught a breaking change in our API contract before it hit prod. That one catch made it worth bookmarking for everyone.”

LS
Leah S.
Tech Lead

“JSONKit is the only online tool I trust with production API payloads. Nothing is uploaded — I paste real tokens and keys without sanitising first. The formatter is instant, no spinner, no lag.”

AM
Alex M.
Senior Backend Engineer

Learn JSON — guides & tutorials

View all articles →
curl

How to POST JSON with curl: The Practical Guide

Send JSON from the command line with curl — the Content-Type header, -d vs --json, posting a file, auth headers, and the quoting mistakes that cause most errors.

Aug 10, 2026 · 7 min read
flatbuffers

FlatBuffers & Cap'n Proto: Zero-Copy Serialization Beyond JSON

When even Protobuf's parse step is too slow, zero-copy formats read fields straight from the buffer with no deserialization. How FlatBuffers and Cap'n Proto work and when they're worth it.

Aug 9, 2026 · 8 min read
sqlite

SQLite JSON Functions: Store and Query JSON with SQL

SQLite has full JSON support built in — json_extract, the -> and ->> operators, json_each for arrays, and JSONB storage. Query JSON columns without a document database.

Aug 8, 2026 · 8 min read

Frequently asked questions

Yes — all 47 tools are free with no usage limits, no rate caps, and no paywalled features. There is no premium tier and there never will be. JSONKit is free for individuals and teams alike.

Yes, completely. Every tool — formatter, validator, code generator, diff, JWT decoder, everything — runs 100% in your browser. Nothing is sent to a server, nothing is logged, and nothing is stored by us. You can safely paste real tokens, API keys, and sensitive production data.

No. Open any tool and start immediately — no signup, no email, no credit card. Your last input is auto-saved to your browser's localStorage so you never lose work between sessions.

Yes. After your first visit, all 47 tools work without an internet connection. Processing runs entirely in JavaScript — no network request is made to format, validate, convert, or generate code from your data.

JSONKit generates typed code in TypeScript interfaces, Go structs (with json tags), Rust structs (serde), Python dataclasses / TypedDict / Pydantic v2, Kotlin data classes, Java POJOs (Jackson or Lombok), C# classes (System.Text.Json or Newtonsoft), Swift Codable structs, and Dart classes with fromJson/toJson. It also generates Zod schemas, Mongoose schemas, and JSON Schema Draft 2020-12.

Yes — JSONKit supports bidirectional conversion between JSON and YAML, JSON and CSV, JSON and XML, and JSON and NDJSON (JSON Lines). You can also convert CSV to SQL, JSON to SQL (with CREATE TABLE and INSERT statements), JSON to Markdown table, JSON to HTML table, and ENV files to and from JSON.

Quite a few: Base64 encoder/decoder (standard, URL-safe, raw), URL encoder/decoder, Hash generator (SHA-256, SHA-512, SHA-1, HMAC), UUID v4 and v7 generator, Unix timestamp converter, Regex tester with live match highlighting, cURL-to-code converter (Go, Python, JS, PHP, Ruby), Number base converter (decimal, hex, binary, octal), HTML escape/unescape, and a plain-text diff tool.

There is no enforced size limit. Processing is bounded only by your browser's available memory. In practice, JSONKit handles files up to 10–20 MB smoothly on most modern devices — more than enough for any real-world API payload or data pipeline sample.

The JSON Schema Validator supports Draft 7 (the most widely deployed version) and the Draft 2020-12 specification. Both drafts are detected automatically from the $schema keyword in your schema — no manual selection needed.

Yes. The JSON Formatter encodes your input into a shareable URL. Anyone with the link can open it and see the same formatted output instantly — no account needed on either end.

Instant results

Every tool processes JSON using native browser APIs. No upload spinner, no loading state. Format a 5 MB file in under 100 ms.

Completely private

Your JSON never leaves your browser. No telemetry on content. Paste production secrets without worry — we literally cannot see them.

Works offline

All processing runs in your browser. Works offline after the first visit — no server, no backend, no data ever transmitted.