Free Online Developer Tools
Format JSON, decode JWTs, test regex, generate UUIDs and hashes — fast, free and private.
100% private: everything runs in your browser and nothing is uploaded.
All developer tools (14)
JSON Formatter & Validator
Pretty-print and validate JSON with precise error locations, key sorting and file upload.
Open toolJSON Minifier
Minify and compact JSON into a single line, validate it and see the size reduction instantly.
Open toolJSON to CSV Converter
Turn JSON arrays into CSV or TSV with nested-object flattening, custom delimiters and a live table preview.
Open toolJSON to YAML Converter
Turn JSON into readable YAML with safe quoting, block-style multi-line strings and 2 or 4-space indentation.
Open toolJSON to TypeScript
Turn any JSON sample into ready-to-use TypeScript interfaces, including nested objects, arrays and optional properties.
Open toolJWT Decoder
Decode any JWT to read its header, payload and claims, check expiration and verify HS, RS, PS or ES signatures.
Open toolBase64 Encoder/Decoder
Encode or decode Base64 strings with full Unicode support
Open toolURL Encoder / Decoder
Encode or decode URLs and query parameters (percent-encoding) with component, full-URL and form modes.
Open toolHash Generator
Calculate MD5, SHA-1, SHA-256 and SHA-512 checksums or HMACs for any text or file and compare them with an expected hash.
Open toolUUID Generator
Create random v4, sortable v7 or time-based v1 UUIDs in bulk with custom formatting, plus a UUID validator.
Open toolUnix Timestamp Converter
Convert epoch time to a date in any time zone and a date back to a Unix timestamp, with ISO 8601 and RFC 2822 output.
Open toolRegex Tester
Build and debug regular expressions with live highlighting, group details, flags, replacement preview and common patterns.
Open toolText Diff Checker
Find the differences between two texts, files or code snippets with line and word-level highlighting.
Open toolCron Expression Generator
Create and check crontab expressions with presets, a plain-language breakdown and the next 10 scheduled run times.
Open toolWhy developers use our tools
Private by design
Your JSON, tokens and text are processed locally in your browser. Nothing is uploaded, logged or stored on our servers.
Instant results
No page reloads and no waiting for a server: results update as you type, even with large inputs.
Free and multilingual
Every tool is free with no sign-up or usage limits, and the whole interface is available in nine languages.
Frequently Asked Questions
Are these developer tools really free?
Yes. Every tool in this collection is completely free to use, with no account, no usage limits and no premium tier.
Is it safe to paste production data or tokens into these tools?
Yes. All processing happens with JavaScript in your browser. Your JSON, JWTs, text and files are never sent to our servers, so they stay on your device.
Do the tools work offline or on mobile?
They work on any modern desktop or mobile browser. Once a page has loaded, the tool itself does not need a network connection to process your data.
Which developer tools are included?
The collection includes a JSON formatter and validator, JSON minifier, JSON to CSV, YAML and TypeScript converters, JWT decoder, regex tester, Unix timestamp converter, UUID generator, hash generator, URL encoder/decoder, Base64 encoder/decoder, cron expression generator and text diff checker.
Can I suggest a new developer tool?
Absolutely. Use the contact page to tell us which utility would save you time, and we will consider it for a future release.
A Developer Toolbox That Lives in Your Browser
Every developer reaches for the same small utilities dozens of times a week: pretty-printing an API response, checking what is inside a JSON Web Token, testing a regular expression before it goes into production, generating a UUID for a fixture or converting a Unix timestamp from a log file. Our Developer Tools collection puts all of these in one place, with a consistent interface, keyboard-friendly inputs and one-click copy and download buttons, so you can stay focused on the code instead of hunting for a trustworthy website.
Unlike many online converters, these tools never send your data to a server. JSON payloads, access tokens, passwords for HMAC and private text diffs are processed entirely with JavaScript inside your browser, which makes them safe to use with production data and internal documents. They are completely free, require no account, work on desktop and mobile, and are available in nine languages, so your whole team can use them.