Free online developer tools
Everyday utilities for working with data and code: format and validate JSON, diff two files, encode and decode, convert spreadsheets, generate model classes and create QR codes. Your data stays in your browser.
Runs on your device 19 tools, all free No sign-up or watermark
- JSON FormatterPaste JSON to check it and format it instantly. Errors point to the exact line and column, and a tree view makes nested data easy to explore.
- Base64 ConverterEncode text or a file to Base64, or decode Base64 back to text or the original file. The result updates as you type.
- URL Encoder & DecoderTurn text into percent-encoded form for use in a URL, or decode %XX sequences back into readable text. The result updates as you type.
- Code Diff CheckerPaste two versions of code or text to see every change highlighted, side by side or inline. It's built on Monaco, the editor inside VS Code.
- String ComparePaste two strings to see exactly which characters differ. It's made for short text such as API keys, hashes, IDs and sentences.
- Lorem Ipsum GeneratorCreate placeholder text for layouts, mockups and test data. Choose paragraphs, sentences or words, and how many you need.
- QR Code GeneratorTurn a link, a UPI payment request, WiFi details or a contact card into a QR code. Pick colours, add a logo and download a PNG at the size you need, or an SVG for print.
- JSON to Model GeneratorPaste a JSON sample and get matching classes or types for your language. The code is generated in your browser as you type.
- CSV / Excel to JSON ConverterTurn CSV or Excel data into JSON, or a JSON array into CSV or an Excel file. Paste text or open a file; everything is converted on your device.
- JWT DecoderPaste a JSON Web Token to see its header and payload as formatted JSON, with expiry and issue times as readable dates. Add the secret or public key to check the signature.
- Hash GeneratorCalculate MD5, SHA-1, SHA-256, SHA-384 and SHA-512 hashes of text or a file, and check a download against its published checksum.
- UUID GeneratorCreate random version 4 or time-ordered version 7 UUIDs, as many as 1,000 at once. Paste any UUID to see its version, variant and embedded time.
- Password GeneratorCreate strong random passwords from the characters you choose, or easy-to-type passphrases made of common words. Each one's strength is shown in bits.
- Unix Timestamp ConverterTurn a Unix timestamp into a readable date in your time zone, UTC, IST or any other zone, or turn a date and time back into a timestamp. The current time ticks along at the top.
- Regex TesterWrite a JavaScript regular expression and see every match highlighted in your text, with numbered and named capture groups. Switch on Replace to preview a substitution.
- Colour ConverterEnter a colour in any CSS format, or pick one, to get it in every other format. The contrast checker shows whether it passes WCAG AA and AAA as text.
- YAML to JSON ConverterPaste YAML to get JSON, or switch direction to turn JSON into YAML. The output updates as you type, and errors point to the line and column to fix.
- SQL FormatterPaste a query to get clean, indented SQL, or switch to Minify to put it on one line. Choose your database dialect so its syntax is read correctly.
- Favicon GeneratorTurn a logo or image into a complete favicon set: favicon.ico, PNG icons, an Apple touch icon, Android icons and site.webmanifest, plus the HTML to paste into your page.
Safe for real data
Paste API responses, tokens or customer exports without sending them anywhere. Everything is processed locally.
Fast feedback
Most tools update as you type, and errors point to the exact line and column.
Proper editors
The diff checker, model generator and CSV converter use Monaco, the editor inside VS Code.
Frequently asked questions
Is it safe to paste API keys or customer data?
The tools run in your browser and don't send your input anywhere. As a general habit, rotate any secret you've pasted into a website you don't control.
Do I need to install anything?
No. Everything runs in a modern browser on Windows, macOS, Linux, Android or iOS.
Which languages can the model generator produce?
TypeScript, C#, Go, Java, Swift, Kotlin, Dart, Python, Rust and C++, generated from a JSON sample.
Can I convert Excel to JSON?
Yes. The CSV / Excel to JSON converter reads .xlsx and .csv files and also turns JSON back into CSV or Excel.