Build, inspect, debug and transform.

Developer Tools

JSON, data formats, encoding, regex, networks and more. 58 tools, all free.

Flagship tool

Explore JSON at any scale

Inspect. Analyze. Visualize. Export. Open a paste or a 1 GB file as a tree, graph, table and field profile — in your browser, never uploaded.

Open JSON Studio

Start from what you have

The tool that fits is suggested as you paste. Nothing leaves this page.

A file opens in the tool for its type: .har HAR.json JSON Studio.csv CSV.log Logs.yaml OpenAPI.md Markdown

Compare two things

Most used

Workflows

Tools that hand their result to the next one. Beside each step, the button that takes you there.

Debug a failing page
Find the failed or slow request in a network capture, replay it, then check the response’s headers.
1. HAR
2. Request builderwith “Open in Request Builder” in HAR
3. Header checkwith “Check response headers” in Request builder
Review an API change
See what a new version breaks for existing clients, browse it, and try an endpoint.
1. API diff
2. OpenAPIwith “Open the new version” in API diff
3. Request builderwith “Build a request” in OpenAPI
Web security review
Grade a response’s headers, then go deeper into its Content-Security-Policy and CORS.
1. Header check
2. CSP checkwith “Evaluate the CSP” in Header check
3. CORSwith “Check CORS” in CSP check
Debug a webhook
Verify a delivery’s signature, read its payload, and replay it against your own endpoint.
1. Webhooks
2. JSON Studiowith “Open in JSON Studio” in Webhooks
3. Request builderwith “Replay with Request Builder” in JSON Studio
Compare and explore data
Find what changed between two JSON documents, then explore the new one as a tree, table or graph.
1. JSON diff
2. JSON Studiowith “Changed JSON in JSON Studio” in JSON diff

JSON

View, query, compare, validate and turn JSON into code.

JSON StudioA JSON workbench: edit with syntax checks, fix broken JSON safely, see it as a 3D graph, cards, tree or table, diff it, validate a schema, query with jq, and convert to CSV, XML, YAML or SQL.500 MB of JSONtree · graph · table · profile

JSON FormatterFormat, validate and minify JSON or JSONC, browse it as a tree, and catch duplicate keys and lost precision.{"a":1,"b":[2]}{ "a": 1, "b": [ 2 ] }

JSON DiffCompare two JSON documents by structure and see every change at its path — key order and spacing ignored.{"qty":2} {"qty":3}~ $.qty 2 → 3

JSON PatchApply or make a JSON Patch (RFC 6902) or merge patch (RFC 7396), and read JSON Pointers — every failed operation named.{"op":"remove","path":"/a"}the patched document

JSONPath TesterQuery JSON with standard RFC 9535 JSONPath — filters, slices and functions — and see every match with its path.$.items[?(@.qty > 2)]matching items

JMESPath TesterTest JMESPath queries — the language of the AWS CLI’s --query — on your JSON, checked against the official compliance suite.Reservations[].Instances[].InstanceId["i-0a1b", "i-0c2d"]

JSON Schema ValidatorCheck JSON against a JSON Schema (draft-04 to 2020-12) and see each problem at its path, with the rule it broke.{"age":"ten"}✗ /age must be integer

JSON Schema GeneratorTurn one or more JSON examples into a draft 2020-12 JSON Schema: types, required keys and formats inferred only where every example agrees.{"id":1}"id": { "type": "integer" }

JSON Schema DiffCompare two JSON Schemas and see which changes accept less, which accept more, and which need a person to check."required": ["a"] → ["a","b"]Narrower: “b” is now required

JSON to TypesTurn a JSON sample into types for TypeScript, Zod, C#, Java, Kotlin, Go, Python, Rust, Swift, Dart, PHP or JavaScript, with optional and nullable fields worked out.{"id":1,"tags":["a"]}id: number; tags: string[]

Mock Data GeneratorMake up to 10,000 rows of realistic test data — names, emails, numbers, dates — as JSON, CSV, SQL inserts or NDJSON, repeatable from a seed.a JSON Schemarows of sample data

Data and formats

CSV of any size, YAML, XML, SQL and the rest — converted, formatted and queried.

CSV WorkbenchOpen a CSV of any size: profile every column, sort, filter, find duplicates, check for broken rows, split it, or convert it to JSON or SQL — on your device.orders.csv, any sizeprofile · duplicates · JSON · SQL

JSON ↔ CSV ConverterTurn a JSON array into a spreadsheet-ready CSV, or CSV into JSON, without losing columns.[{"a":1,"b":2}]a,b ⏎ 1,2

YAML ↔ JSON ConverterConvert YAML to JSON and back, with anchors, merge keys and several documents handled.{"a":[1,2]}a: ⏎ - 1 ⏎ - 2

Query String ↔ JSONTurn a URL’s query string into JSON and JSON into a query string — browser or PHP/Rails/qs bracket rules, chosen by you.?tag=a&tag=b&page=2{ "tag": ["a","b"], "page": "2" }

XML Formatter and ValidatorFormat, minify and check XML for well-formedness, with the exact line and column of any error. Text and mixed content are never changed.<a>1</a><a> ⏎ 1 ⏎ </a>

SQL FormatterBeautify SQL for PostgreSQL, MySQL, SQL Server, Oracle, BigQuery and more — strings and comments untouched.select id from t where x=1SELECT id FROM t WHERE x = 1

SQL PlaygroundRun real SQLite in your browser: write a query against a sample shop or your own tables, and see every result set, the schema and the query plan.SELECT count(*) FROM tSQLite, in your browser

CSS Formatter and MinifierBeautify or minify CSS, including nesting and custom properties, with unclosed blocks and strings pinpointed. Values are never rewritten.a{color:red}a { color: red; }

Markdown PreviewA Markdown workspace: editor and live preview side by side, tabs and folders, maths, Mermaid diagrams, exports. Saved in your browser; nothing is uploaded.**bold** _it_bold it, rendered

API and HTTP

Build requests, read and compare API descriptions, look up what a status means.

HTTP Request BuilderBuild an HTTP request — method, URL, query, headers, auth and body — and copy it as cURL, fetch, axios, Python, HTTPie or a .http file. Nothing is sent.POST /v1/orders + bearer + JSONcurl · fetch · HTTPie · .http

cURL ConverterTurn a curl command into JavaScript fetch, axios or Python requests — headers, body, auth and forms included.curl -X POST …fetch(…), Python, Go

OpenAPI Viewer and ValidatorRead an OpenAPI 3.0 or 3.1 description as API documentation and check it against the official schemas, with broken references and path parameters found too.openapi.yaml✓ valid 3.1 · 4 operations

OpenAPI Diff — Breaking ChangesCompare two versions of an OpenAPI description and see which changes break existing clients, which to check, and which are safe — with a report for the pull request.v2.4 → v2.56 breaking · 1 check · 4 safe

HTTP Status CodesEvery HTTP status code with what it means, when to send it and the RFC section that defines it — searchable by number or words.418I'm a teapot

Web and security

Response headers, cookies, Content-Security-Policy, CORS and webhook signatures.

HTTP Headers AnalyzerPaste a response’s headers and see what they protect and what they leave open: HSTS, CSP, framing, cookies, caching, CORS and what the server gives away — graded and explained.curl -I https://…grade F · 3 to fix · 7 to check

CSP EvaluatorCheck a Content Security Policy the way browsers read it: which directive governs each kind of resource, and what lets injected script run — unsafe-inline, wildcards, missing object-src and base-uri, bad syntax.script-src 'unsafe-inline' data:2 to fix · 4 to check

CORS CheckerFind out why a browser blocks a cross-origin request: whether it needs a preflight, which header the preflight or response is missing, and which headers your JavaScript can read — step by step, by the Fetch standard.POST + Authorization, credentialsblocked: preflight lacks Authorization

Webhook Signature CheckerPaste a webhook’s headers and body to see the provider and event and check its signature with your secret — GitHub, Stripe, Razorpay, Slack, Shopify, Standard Webhooks, GitLab or any HMAC. The secret stays on this page.X-Hub-Signature-256 + body + secretGitHub ping · valid signature

Debugging and observability

Network captures, logs of any size, and what changed between two texts.

HAR ViewerOpen a browser HAR file: a waterfall of every request, failures and slow calls, headers and bodies, copy as cURL — and a copy with cookies and tokens removed, safe to share.network.harwaterfall · failures · redacted copy

Log ViewerOpen a log file of any size: filter by level, time and text, fold stack traces, group repeated errors and follow trace IDs.app.log, any sizelevels · grouped errors · trace IDs

Text Diff CheckerCompare two texts side by side or unified, with changed words highlighted and a patch git can apply.old text, new text− removed + added

Encode, hash and secure

Encodings, hashes, tokens, IDs and passwords.

Base64 Encoder & DecoderEncode text or files to Base64 or a data: URI, and decode it back — text, or the file inside with its type and a preview.helloaGVsbG8=

URL Encoder & DecoderPercent-encode or decode text for URLs, and break a URL into its parts and query parameters.a b&ca%20b%26c

HTML Entity Encoder & DecoderEscape text for HTML or decode &,  , ₹ and every other entity back to characters.

String Escape and UnescapeEscape text for a JSON or JavaScript string, a SQL literal, a shell argument, a CSV cell or a regular expression — and read escaped text back, exactly as each format defines it.say "hi""say \"hi\""

Hash GeneratorMD5, SHA-1, SHA-256 and SHA-512 of text or a file, HMAC, and a checksum match check.abcSHA-256 ba7816bf…

JWT DecoderDecode a JSON Web Token, verify its signature with a secret, PEM or JWK Set, and make signed test tokens — in your browser, never uploaded.eyJhbGciOiJIUzI1NiJ9…{ "alg": "HS256" }

Password GeneratorStrong random passwords and memorable passphrases, made on your device with cryptographic randomness.20 characters, all setsa strong random password

UUID GeneratorGenerate UUID v4, time-ordered v7, ULID and name-based v5 in bulk, and decode any ID’s version and creation time.version 4 or 7a fresh UUID

Utilities

Patterns, diagrams, subnets, permissions, schedules, times and numbers.

Regex TesterTest a JavaScript regular expression live: highlighted matches, groups, flags and replace./\d+/g on "a1 b22 c333"3 matches

Regex VisualizerDraw any JavaScript regular expression as a railroad diagram, read it in plain English, and try it on your own text./colou?r/railroad diagram

Diagram StudioFlowcharts, sequence, ER, class, Gantt and 15 more Mermaid diagrams, drawn as you type. SQL → ER, OpenAPI or JSON → class diagram, SVG, PNG and PDF. On your device.CREATE TABLE … or A --> BER diagram, flowchart, SVG

IP Subnet Calculator (IPv4 and IPv6)Network, broadcast, usable host range, netmask and wildcard for any IPv4 or IPv6 block — exact counts, address types, splitting and an in-range check.10.0.0.0/24256 addresses

Chmod Calculator (Unix Permissions)Convert Unix file permissions between octal (755), ls -l (rwxr-xr-x) and chmod’s u=rwx form, with setuid, setgid and sticky bits and a plain-English meaning.755rwxr-xr-x

Cron Expression ExplainerTurn a cron schedule into plain English and see its next run times.0 9 * * 1-509:00, Monday to Friday

Unix Timestamp ConverterUnix time to a readable date and back, in seconds, milliseconds or nanoseconds, in any time zone.170000000014 Nov 2023, 22:13:20 UTC

Number Base ConverterBinary, octal, decimal, hex and any base to 36 — exact for huge numbers, with two’s complement and IEEE 754 floats.2550xFF · 0b11111111

.gitignore GeneratorBuild a .gitignore from GitHub’s official templates, then test whether any path would be ignored.Node + macOSnode_modules/ .DS_Store

CSS, colour and SVG

Gradients, shadows, corners, glass, buttons and animations with live previews; colours, contrast and palettes; SVG files cleaned, made smaller and shown safely.

CSS Gradient GeneratorNewDesign linear, radial and conic CSS gradients with up to eight colour stops and OKLCH blending, see them live, and copy the CSS with a fallback colour.#ff7a18 → #af002dlinear-gradient(135deg, …)

CSS Box Shadow GeneratorNewBuild CSS box shadows from up to five layers — offset, blur, spread, colour, opacity and inset — with a live preview and copyable CSS.y 4 · blur 12 · 12%box-shadow: 0 4px 12px …

CSS Border Radius GeneratorNewRound each corner separately, in pixels or percent, with elliptical corners for blob shapes, and copy the shortest border-radius shorthand.8 4 8 4border-radius: 8px 4px

Glassmorphism CSS GeneratorNewMake a frosted-glass panel with backdrop-filter: tint, opacity, blur, saturation, border and shadow, previewed over a colourful background, with copyable CSS.blur 14 · 18% whitebackdrop-filter: blur(14px)

CSS Button GeneratorNewDesign a CSS button — colours, padding, corners, border, type, shadow and hover — with hover, focus and disabled states, and the text contrast checked against WCAG.blue · 8px · bold.button { … } :hover :focus-visible

CSS Animation Generator (Keyframes)NewMake a CSS animation — fade, slide, zoom, bounce, pulse, shake, spin or flip — with duration, delay, easing and repeats, and a reduced-motion rule built in.slide up · 600 ms@keyframes + animation

Colour Converter and Contrast CheckerConvert colours between HEX, RGB, HSL and OKLCH, check WCAG contrast, and get the nearest colour that passes.#6d28d9rgb(109 40 217)

Colour Palette GeneratorNewBuild complementary, analogous, triadic and other palettes, plus a 50–950 tint and shade scale, from one colour in OKLCH, with contrast shown and CSS variables to copy.#3b82f6, triadic3 colours + 50–950 scale

SVG Viewer and CleanerNewView an SVG safely, strip scripts, event handlers and outside links, tidy away editor clutter, and copy it as a file, a data URI or a CSS background.<svg onload=…>safe SVG · data URI