Free Developer Tools Online

Developer tools that run on your computer — format JSON, test regular expressions, decode JWTs, encode Base64, and more. Nothing uploads. Works on bad wifi or no wifi.

Quick browser-based utilities for everyday development tasks — format and validate JSON, test regular expressions with live match highlighting, decode and inspect JWTs, encode or decode Base64 strings, convert UNIX timestamps, generate UUIDs, minify CSS and JavaScript, and create cron expressions. Everything runs on your computer, which matters when debugging production tokens, sensitive config files, or API payloads you would rather not paste into an online service. The full developer toolkit is below.

Format

JSON Formatter

Paste messy JSON — get it beautifully formatted, validated, and unescaped. Runs entirely in your browser.

XML Formatter

Format or minify XML with syntax highlighting — right in your browser. Validates structure and highlights errors.

YAML Formatter

Format, validate, and convert YAML — right in your browser. Paste messy YAML and get it beautified with error highlighting.

Code Minifier

Minify HTML, CSS, and JavaScript — right in your browser. See original vs minified size with percentage reduction.

Encode

Base64 Encoder/Decoder

Encode text or files to Base64, or decode Base64 back — right in your browser. Supports text and file mode.

URL Encoder/Decoder

Encode or decode URLs and query strings — right in your browser. Uses encodeURIComponent and decodeURIComponent.

HTML Entity Encoder/Decoder

Encode special characters to HTML entities or decode them back — right in your browser. Handles &, <, >, ", and '.

Generate

Hash Generator

Generate SHA-1, SHA-256, and SHA-512 hashes from any text — right in your browser using the Web Crypto API.

UUID Generator

Generate random UUID v4 identifiers — right in your browser. Generate one or many at once with one-click copy.

Password Generator

Generate strong, random passwords — right in your browser. Customize length, characters, and complexity.

Lorem Ipsum Generator

Generate placeholder text in paragraphs, sentences, or words — right in your browser. Copy with one click.

Cron Expression Generator

Build cron expressions with a visual editor — right in your browser. See a human-readable schedule and the next execution times.

Convert

JSON to CSV

Convert a JSON array of objects to CSV format. Handles nested keys by flattening. Download as .csv.

CSV to JSON

Convert CSV text to a JSON array of objects. Auto-detects headers. Download as .json.

Unix Timestamp Converter

Convert between Unix timestamps and human-readable dates. See current timestamp live.

Test

Regex Tester

Test regular expressions with live matching and group highlighting. Supports global, case-insensitive, multiline, and dotAll flags.

JWT Decoder

Decode JSON Web Tokens to inspect header, payload, and signature. Verify signatures with Web Crypto API.

Design

Color Picker

Pick any color and get its HEX, RGB, and HSL values. Copy color codes with one click.

CSS Gradient Generator

Create beautiful CSS gradients with live preview. Linear and radial gradients with multiple color stops.

Code to Image

Turn code snippets into beautiful images. Choose themes, adjust padding, and export as PNG.

Favicon Generator

Generate favicons from images or text. Preview at all sizes and download as ICO or PNG.

Frequently asked questions

Is it safe to paste a JWT or API token here?: Yes. JWT Decoder and all other dev tools run entirely in your browser. Tokens are not transmitted anywhere — you can verify this in DevTools Network tab, which will show zero outgoing requests when you use the tools.
Does the JSON formatter validate schema or just syntax?: It validates syntax (RFC 8259) and pretty-prints with configurable indentation. Schema validation against a JSON Schema definition is not currently supported.
Can I use these tools in a corporate environment with strict firewall rules?: Yes. After the initial page load, the dev tools make no outbound network requests. They will function on air-gapped machines as long as the page is cached.