Instant format & validate
Beautify with 2 or 4-space indent, or minify to one line. Invalid JSON? We point at the exact line and column — and offer one-click repair for trailing commas, single quotes, and comments.
JSONStudio by Upwwards — Free online JSON formatter, validator, viewer, converter and diff. 100% client-side, works offline, no sign-up.
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{
"status": "ok",
"meta": {
"page": 1,
"perPage": 20,
"total": 137,
"took_ms": 42
},
"results": [
{
"id": "usr_8af2",
"name": "Ada Lovelace",
"role": "admin",
"active": true,
"tags": [
"founder",
"math"
],
"lastSeen": "2026-06-01T09:24:00Z"
},
{
"id": "usr_4c19",
"name": "Alan Turing",
"role": "engineer",
"active": true,
"tags": [
"compute"
],
"lastSeen": "2026-05-28T17:02:00Z"
},
{
"id": "usr_d77b",
"name": "Grace Hopper",
"role": "engineer",
"active": false,
"tags": [
"compiler",
"navy"
],
"lastSeen": null
}
]
}02 — what's inside
Everything you reach for, nothing you don't.
See structure, not soup
A collapsible tree for navigating, a node-graph for grasping shape at a glance, and a real sortable table when your JSON is a list of records. Filter, expand, copy any path.
Convert in one click
Turn JSON into YAML, CSV, XML, or fully-typed TypeScript interfaces. Copy or download the result. No round-trip to a server, no upload.
Diff two documents
Drop the before and after side by side and get a clean, path-addressed list of what was added, removed, and changed. Perfect for API responses and config drift.
Your data never leaves
Every operation runs in your browser with zero network calls. No accounts, no logging, no telemetry on your payloads. Close the tab and it's gone.
Built for fast hands
Keyboard shortcuts for every core action, drag-and-drop file open, instant view switching, and a layout that gets out of your way. It's a workspace, not a webpage.
03 — conversions
One source of truth.
26 different formats.
JSON goes in. Whatever your next tool needs comes out — generated locally, instantly, and ready to copy or download. No round-trip to a server, ever.
total_targets26+// growing
Data formats
06- →YAML
- →TOML
- →XML
- →CSV
- →TSV
- →JSON Lines
Tables
02- →Markdown table
- →HTML table
Typed code
07- →TypeScript
- →Go struct
- →Rust struct
- →Kotlin
- →Java class
- →C# record
- →JSON Schema
Code literals
03- →Python dict
- →PHP array
- →Ruby hash
Web & encoding
04- →Query string
- →URL-encoded
- →Base64
- →Escaped string
Shape
04- →Minified
- →Flatten (dot keys)
- →Unflatten
- →SQL INSERT
04 — questions
The short answers.
Everything people ask before they trust a JSON tool with their data.
Yes — completely free, with no sign-up, no account, and no usage limits. It's a tool we maintain as part of Upwwards.
Entirely. JSONStudio is 100% client-side: formatting, validation, conversion, and diffing all happen in your browser using JavaScript. Your data is never uploaded to a server, logged, or sent anywhere.
Once the page has loaded, every feature works without a network connection. The whole engine runs locally, so you can format and inspect JSON on a plane or behind a firewall.
More than twenty targets: YAML, TOML, XML, CSV, TSV and JSON Lines for data interchange; Markdown and HTML tables; typed code for TypeScript, Go, Rust, Kotlin, Java, C#, and JSON Schema; literal output for Python, PHP, and Ruby; Query string, URL-encoded, Base64 and escaped-string encodings; plus SQL INSERT statements and flatten / unflatten transformations.
Paste it in and JSONStudio shows the exact line and column of the first error. The Repair button automatically fixes common problems — trailing commas, single quotes, comments, and unquoted keys — then re-validates.
Yes. JSONStudio is built for speed and handles multi-megabyte files comfortably. You can open files by dragging them onto the editor or with the file button.
The tree is for navigating and collapsing nested structure; the table renders arrays of objects as sortable rows; the graph lays your JSON out as connected nodes so you can see its overall shape at a glance.
Yes — paste a sample response into the editor, switch to Convert, and pick TypeScript, Go, Rust, Kotlin, Java, C#, or JSON Schema. Field names are normalised, types are inferred, and nested objects become their own named types.
JSONStudio is built and maintained by Upwwards — an independent, remote-first custom software development company that builds, supports, and rescues software. If you need a web app shipped, production software supported, or an AI-generated codebase stabilized through Patchlane, you can talk to Upwwards.
What is JSON, and why does formatting matter?
JSON — JavaScript Object Notation — is the lingua franca of modern APIs, configuration files, and document databases. It's a small, strict format built from objects, arrays, strings, numbers, booleans, and null. Strict, because a stray comma or unquoted key is the difference between a working integration and a 4 a.m. page.
A good JSON formatter does three things at once. It beautifies the document with consistent indentation so a human can read it; it validates the syntax and tells you exactly where the first error is; and it shows you structure — the shape of the data, not just the bytes. JSONStudio does all three the moment you paste, and it does it without sending a single character to a server.
How to use JSONStudio
- Paste, type, or drop a file. The editor on the left accepts up to several megabytes comfortably and updates the view on every keystroke. Drag a
.jsonfile directly onto it, or use the upload button in the toolbar. - Read the status bar. Valid JSON shows a green check with a node count, key count, and depth. Invalid JSON shows the exact line and column of the first error — click the message to jump the cursor straight there.
- Pick a view. Formatted shows colour-coded code. Tree is a collapsible navigator with copy-path. Table renders an array of objects as a sortable spreadsheet. Graph lays the whole document out as connected nodes.
- Format, minify, sort, or repair. The actions on the input header beautify with 2 or 4-space indent, strip whitespace, sort keys A→Z, or auto-fix common problems — trailing commas, single quotes, comments, unquoted keys, smart quotes — and re-validate.
- Switch to Convert to pick one of twenty-plus targets — YAML, TOML, TypeScript, Go, SQL, Markdown table, Base64, and many more.
- Switch to Diff to compare two documents side by side. The result is a clean, path-addressed list of additions, removals, and changes.
⌘ — tip Press ⌘/ at any time to see every keyboard shortcut. Formatting is ⇧⌘F, minifying is ⌘M, repair is ⇧⌘R.
Every converter, explained
JSONStudio converts JSON to more than twenty other shapes — from interchange formats and typed code to encodings and tables. Each conversion runs locally, in milliseconds.
JSON → YAML
Turn JSON into clean, human-readable YAML — the configuration language used by Kubernetes, GitHub Actions, Ansible, Docker Compose, and most modern CI systems. Comments and anchors aren't required for round-trip, so the conversion stays predictable.
JSON → TOML
Emit a valid TOML document, the format favoured by Rust's Cargo, Python's pyproject.toml, and Hugo. Top-level scalars become assignments; nested objects become tables; arrays of objects become array-of-tables blocks.
JSON → XML
Generate well-formed XML with safe element names, escaping reserved characters, and pluralised wrappers for arrays. Useful for SOAP, RSS, sitemaps, and legacy enterprise integrations.
JSON → CSV / TSV
If your JSON is an array of objects, JSONStudio derives the column set automatically, quotes only the cells that need it, and emits RFC 4180-compatible CSV (or tab-separated values).
JSON → JSON Lines (NDJSON)
One object per line — the streaming format used by ElasticSearch, BigQuery loads, OpenAI fine-tuning datasets, and most log pipelines. Drop in an array and get newline-delimited JSON back.
JSON → Markdown table
Render an array of objects as a GitHub-flavoured Markdown table — perfect for READMEs, PR descriptions, and documentation. Pipes inside cells are escaped automatically.
JSON → HTML table
Produce semantic table/thead/tbody markup, with HTML-escaped cells, ready to paste into an email, a CMS, or a static site.
JSON → TypeScript
Generate strongly-typed interface declarations from a sample. Nested objects become their own named interfaces; mixed-type arrays become unions; primitive types are inferred.
JSON → Go struct
Get idiomatic Go struct definitions with capitalised exported field names and json tags — drop straight into your service code.
JSON → Rust struct
Produce serde-ready Rust structs with #[derive(Serialize, Deserialize)] and #[serde(rename)] when the snake_case form differs from the original key.
JSON → Kotlin data class
Output Kotlin data classes — handy for Android, Ktor, or any JVM service that uses kotlinx.serialization or Moshi.
JSON → Java class
Generate a POJO scaffold with private fields and camelCase names. Ideal as a starting point for Jackson or Gson deserialization.
JSON → C# record
Concise positional C# records modelling your shape — fine for ASP.NET responses, EF projections, or DTOs.
JSON → JSON Schema
Derive a Draft 2020-12 schema describing your data, ready to use for validation, code generation, OpenAPI components, or contract testing.
JSON → Python dict
A pretty-printed Python dict literal with True/False/None — paste directly into a script or notebook without round-tripping through json.loads.
JSON → PHP array
PHP short-array syntax with single-quoted strings, ready for Laravel, Symfony, or a flat config file.
JSON → Ruby hash
Ruby hash literal with hashrocket arrows, the standard form for fixtures, seeds, and Rails console paste-ins.
JSON → SQL INSERT
An array of objects becomes a sequence of parameterised INSERT statements. Column order is stable across rows; values are escaped; nested objects are stored as JSON.
Query string · URL-encoded · Base64
Three small encodings for moving JSON across the wire — application/x-www-form-urlencoded, single-encoded JSON, and Base64 (UTF-8 safe). Round-trip safe and copy-friendly.
Flatten / Unflatten
Collapse a nested object into a single-level map of dot-notation keys (a.b[0].c → value) or expand the same form back into nested JSON. Useful for diffing, spreadsheet exports, and feature stores.
Common use cases
Debugging API responses
When a backend returns a giant blob, JSONStudio lets you collapse it down to the part that matters, copy a single path, or instantly diff it against the previous response to see what changed.
Cleaning up exported data
Database dumps, third-party exports, and AI-generated payloads often arrive broken. Repair handles trailing commas, unquoted keys, single quotes, comments, and Python-ish literals — and shows you the result.
Generating types from a sample
Paste one example response, switch to Convert, and pick TypeScript, Go, Rust, Kotlin, Java, C#, or JSON Schema. Field names are normalised, types are inferred, nested objects become their own named types.
Exporting to a spreadsheet
An array of objects becomes well-formed CSV or TSV with a single click — quoted cells where needed, stable column order across rows.
Documenting an endpoint
Markdown and HTML table converters drop straight into READMEs, Notion docs, and PR descriptions. JSON Schema gives you a contract; SQL INSERT gives you fixtures.
Working offline
JSONStudio is a single self-contained page. Once it has loaded, every feature works without a network connection — on a flight, behind a firewall, or in an air-gapped environment.
Privacy & security model
The most important thing a JSON tool can do is not see your JSON. JSONStudio is built around that idea. Parsing, formatting, validation, repair, every conversion, the diff engine, the tree and graph views — all of it runs in your browser. There is no upload step, no analytics on your payload, no logging, no telemetry tied to the content you paste. Close the tab and the data is gone.
If you ever need to confirm this, the network panel of your browser's devtools will show zero requests after the page has loaded. The whole engine fits inside this page and stays here — a deliberate, privacy-first choice by Upwwards, the software company that builds and maintains JSONStudio.
Built by Upwwards
JSONStudio is a small, sharp utility from Upwwards — an independent custom software development company that builds, supports, and rescues software. We ship the tools we wished existed when we were on call, on a deadline, or three nested objects deep in someone else's API.
Upwwards works in two arms — the products we build and own, and the services we run for other teams. We build custom web apps, SaaS platforms, and internal tools; we support production software with ongoing maintenance, bug fixes, and dependency upgrades; and we consult on architecture, stack choices, and hiring — remote-first, with no account managers between you and the engineers. Through Patchlane, we also review and stabilize AI-generated codebases so they can reach production safely.
If you've got a project that needs to ship, a system that's misbehaving, or a team that needs a hand, talk to Upwwards. And if you just want a great JSON tool — that's what this is.
★ — built by upwwards
A small, sharp tool from a company that ships.
JSONStudio is built and maintained by Upwwards — an independent custom software development company with two arms: the products it builds and owns, and the services it runs for teams who need web apps shipped, software supported, or AI-generated codebases rescued. The motto is simple — build, support, and rescue software.
Build
Custom web apps, SaaS platforms, and internal tools — shipped by the engineers who design them.
Support
Ongoing maintenance, bug fixes, and dependency upgrades that keep production software healthy.
Consult
Straight technical advice on architecture, stack choices, and hiring — no account managers.
Patchlane
Review and stabilization for AI-generated codebases that need to reach production safely.