Developer tools that never send your data anywhere

Format, validate, convert and decode JSON, XML, YAML, Markdown, Base64, JWTs and more. Every tool on this site runs entirely in your browser, so API responses, tokens and config files stay on your machine.

No sign-up
Works offline once loaded
Handles multi-megabyte files
Light and dark mode

JSON

JSON FormatterBeautify, validate, minify and explore JSON in an interactive tree.JSON ValidatorCheck JSON syntax and pinpoint the exact line of every error.JSON ViewerExplore large JSON documents as a collapsible tree.JSON MinifierStrip whitespace from JSON to shrink payloads.JSON Escape / UnescapeEscape text into a JSON string literal, or unescape it back.

XML

XML FormatterPretty-print, validate and minify XML with a tree view.XML to JSONConvert XML documents into clean, readable JSON.JSON to XMLTurn JSON objects into well-formed XML.

YAML

YAML FormatterValidate, format and explore YAML configuration files.JSON to YAMLConvert JSON into clean YAML for Kubernetes, CI and config files.YAML to JSONConvert YAML configuration into formatted JSON.

Markdown

Markdown EditorWrite Markdown with a live GitHub-style preview.

Converters

JSON to CSVFlatten JSON arrays into CSV for Excel and Google Sheets.CSV to JSONConvert CSV or TSV rows into a JSON array of objects.

Encoders & Decoders

Base64 Encode / DecodeEncode and decode Base64 and Base64URL, including UTF-8 and files.URL Encoder / DecoderEncode, decode and parse URLs and build query strings.JWT DecoderDecode JSON Web Token headers and payloads and check expiry.

Generators

UUID GeneratorGenerate random v4 and time-ordered v7 UUIDs in bulk.Hash GeneratorCompute SHA-256, SHA-1, SHA-384 and SHA-512 hashes of text or files.

Text & Time

Diff CheckerCompare two texts, JSON or XML files and highlight differences.Epoch ConverterConvert Unix timestamps to dates and back, in any timezone.

Private by design

The tools are plain JavaScript that runs on your device. When you click Format or Decode, nothing is uploaded: you can confirm this in your browser's Network tab. That makes the site safe for production payloads, customer data and access tokens that should never be pasted into a server-side formatter.

Fast with large files

Heavy work such as parsing a 20 MB JSON export happens in a background Web Worker, and tree views render only the rows on screen. Pages are small, load no frameworks and keep working without a connection once they have loaded.

Built for everyday debugging

Pretty-print an API response, find the line where a config file breaks, decode a JWT to check its expiry, compare two payloads, or convert YAML to JSON for a script. Each tool page also explains the format, the common errors and how to fix them.

Guides from the blog

"Unexpected token in JSON": causes and fixesHTML error pages, empty bodies, trailing commas and defensive parsing in JS and Python.
JWT explained: structure, claims and common mistakesSigning algorithms, verification steps and the vulnerabilities to avoid.
Markdown tables: syntax, alignment and tricksEscaping pipes, line breaks in cells and the HTML fallback.
Complete guide to JSON formatting and validationData types, the most common syntax errors and how to fix them.
YAML vs JSON: key differences and when to use eachReadability, comments, the Norway problem and performance.
URL encoding explainedReserved characters, encodeURI vs encodeURIComponent and double-encoding bugs.

All articles →

Frequently Asked Questions

Is my data uploaded when I use these tools?

No. Formatting, validation, conversion, encoding and decoding all run as JavaScript inside your browser tab. The text you paste is never sent to our servers. The site itself uses Google Analytics and Google AdSense, which set cookies to measure visits and show ads; see the privacy policy for details.

Are the tools free?

Yes. Every tool is free with no account, usage limits or paid tier. The site is supported by advertising.

Do the tools work offline?

Once a tool page has loaded, its processing code is in your browser, so you can keep formatting and converting even if your connection drops.

How large a file can I format?

The JSON tools comfortably handle files of tens of megabytes on a typical laptop because parsing runs in a Web Worker and the tree view only renders visible rows. The practical limit is your device's memory.

Which browsers are supported?

Current versions of Chrome, Edge, Firefox and Safari on desktop and mobile.