View, edit, query, and convert JSON, YAML, CSV, XML, Mermaid, Markdown & MDX in one local-first workspace. Tree/table/diagram views, jq/SQL/XPath queries, schema validation, diff. Nothing is uploaded; no account needed.
A startup from San Francisco, the United States.
This page is designed to help you find out whether Prettify.tools is good and if it is the right choice for you.
Prettify is a viewer and editor for the data formats developers actually wrestle with: JSON, YAML, CSV, XML, Mermaid, Markdown, MDX, and HTML, in one fast, local-first workspace.
Unlike most online formatters, Prettify is built for devs by devs. Parsing, editing, validation, queries, and conversion all run on your device, so it's safe for API responses, customer data, tokens, and internal config; it also works offline as an installable PWA or a native macOS app (Windows and Linux builds are also available).
Open a file and switch between Tree, Table, Raw and Diagram views. Format and validate; fix broken JSON. It accepts comments and trailing commas and keeps large numbers exact; search and replace with regex; convert between JSON, YAML, CSV and XML; run jq filters, query CSV with SQL, or query XML with XPath; validate against a JSON Schema; diff two documents; generate TypeScript, Go, Kotlin, Rust or JSON Schema types from a sample; and share by link. Prettify also edits Markdown and MDX with Prettier formatting and a live preview, includes a Mermaid editor with SVG/PNG export, reads RSS/Atom feeds, and has a dedicated editor for Claude SKILL.md files.
The free tier is generous and has no time limit. Prettify Pro is a one-time US$19.99 purchase, no subscription, unlocking the query engines, JSON Schema validation, the Diagram view, diff, split view, full document history, and Skill Check.
Made by Off Leash Labs, an indie studio in San Francisco.
Listed in
Supported formats
JSON, YAML, CSV, XML, Mermaid, Markdown, MDX, HTML
Views
Tree, Table, Raw, and Diagram (node graph) views
Query engines
jq, SQL for CSV, XPath for XML (Pro)
Validation
Syntax validation for all formats, plus JSON Schema validation (Pro)
Conversion
Convert between JSON, YAML, CSV and XML, including JSONL
Diff
Compare two documents side by side (Pro)
Type generation
Generate TypeScript, Go, Kotlin, Rust or JSON Schema types from a sample
Markdown & Mermaid
Prettier formatting and live preview; Claude SKILL.md editor with Skill Check (Pro)
Pricing
Free tier with no time limit; Pro is $19.99 one-time, lifetime
Privacy
Local-first, files are never uploaded; everything runs on your device
Prettify is local-first: your documents are never uploaded to a server. Everything, parsing, editing, validation, queries, conversion, runs entirely on your device, so it's safe for sensitive data like API responses with tokens, customer records, and internal config files. It also covers eight formats in one workspace (JSON, YAML, CSV, XML, Mermaid, Markdown, MDX, HTML) instead of a separate single-purpose tool per format, and works offline as a web app or native desktop app.
Most online JSON tools upload your file to their server and handle only one format. Prettify keeps your data on your device, handles eight formats with Tree, Table, and Diagram views, and goes well beyond formatting: jq, SQL, and XPath query engines, JSON Schema validation, document diff, and type generation. Pro is a one-time $19.99, no subscription, and the free tier has no time limit.
Developers who open, inspect, fix, and reshape data files by hand, API responses, config files, CSV exports, logs, and don't want to paste sensitive data into third-party servers. Also technical writers working in Markdown/MDX and people writing Claude Skills.
Prettify is made by Off Leash Labs, an indie studio in San Francisco. It grew out of everyday frustration with online formatters that upload your files, quietly corrupt large numbers, and each handles only one format; so Prettify was built to do the whole job locally, across formats, with no account and no server.
TypeScript, with Tauri for the native desktop apps. Prettier for formatting, Ajv for JSON Schema validation, quicktype for type generation. The jq engine is hand-written in TypeScript; no WebAssembly.
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