Free online Developer Tools
Formatters, encoders, decoders and generators for everyday coding. 51 tools, all free and private.
51 tools 100% free No installation Privacy focused
JSON Formatter & ValidatorFormat, beautify, validate and minify JSON with clear error messages and line numbers.Base64 Encode / DecodeEncode text to Base64 or decode Base64 back to text, with full UTF-8 and URL-safe support.URL Encode / DecodePercent-encode text for safe use in URLs and query strings, or decode encoded URLs.UUID GeneratorGenerate cryptographically secure random UUID v4 / GUID values in bulk.JWT DecoderDecode a JSON Web Token to read its header, payload and expiry time. Nothing is sent to a server.Regex TesterTest regular expressions live with match highlighting, capture groups and replace preview.Diff CheckerCompare two texts or code files side by side and highlight added and removed lines and words.JSON ⇄ CSV ConverterConvert JSON arrays to CSV for Excel, or CSV back to JSON. Handles quotes, commas and nested objects.CSS Gradient GeneratorCreate beautiful linear and radial CSS gradients visually and copy the code.Markdown Editor & PreviewWrite Markdown with a live preview and convert it to clean HTML. Supports tables, code blocks and GFM.CSV ⇄ Excel ConverterConvert CSV files to Excel XLSX and Excel spreadsheets to CSV, with sheet selection and preview.YAML ⇄ JSON Converter & FormatterConvert YAML to JSON and JSON to YAML, validate syntax and reformat YAML files.JavaScript, CSS & HTML BeautifierBeautify minified or messy JavaScript, TypeScript, JSON, CSS and HTML with clean indentation.Code Screenshot (Snippet Image)Turn code snippets into beautiful images with syntax colors, window frame and gradient background.JSON Viewer (Tree)Explore JSON as a collapsible tree with types, counts and search, and copy the path of any value.HTML Entity Encode / DecodeEscape <, >, &, quotes and special characters into HTML entities, or decode entities back.HEX to RGB Color ConverterConvert colors between HEX, RGB, HSL and CMYK with a live picker and CSS-ready output.Unix Timestamp ConverterConvert Unix epoch timestamps to human-readable dates and dates back to timestamps.CSS MinifierMinify CSS by removing comments, whitespace and unnecessary characters to make stylesheets load faster.HTML MinifierCompress HTML by removing comments and extra whitespace while keeping pre, textarea and script content safe.JavaScript MinifierRemove comments and whitespace from JavaScript to reduce file size, while keeping strings and regexes intact.SQL FormatterFormat messy SQL queries with clean line breaks, indentation and uppercase keywords.JSON ⇄ XML ConverterConvert JSON to well-formed XML and XML back to JSON, including attributes and repeated elements.Binary, Hex & Decimal ConverterConvert numbers between binary, octal, decimal, hexadecimal and any base from 2 to 36. Supports big numbers.CSS Box Shadow GeneratorCreate soft, layered or inset CSS box shadows visually and copy the code.CSS Border Radius GeneratorSet rounded corners individually and create organic blob shapes with CSS border-radius.Color Contrast CheckerCheck the contrast ratio between text and background colors against WCAG 2.1 AA and AAA standards.Cron Expression GeneratorBuild cron expressions, read them in plain English, and see the next run times.HTML, CSS & JS Live EditorWrite HTML, CSS and JavaScript and see the result live in a sandboxed preview. Great for quick experiments.JWT Encoder (HS256)Create a signed JSON Web Token from a JSON payload and secret using HS256, HS384 or HS512.Mock Data GeneratorGenerate realistic fake test data — names, emails, phones, cities, dates — as JSON, CSV or SQL inserts.XML FormatterFormat, indent and validate XML documents, or minify them into a single line.TOML ⇄ JSON ConverterConvert TOML configuration files (Cargo.toml, pyproject.toml) to JSON and back.JSON Compare (Diff)Compare two JSON documents and list added, removed and changed keys with their paths.JSON Schema GeneratorGenerate a JSON Schema (draft 2020-12) from sample JSON, with types, required fields and nested objects.cURL Command GeneratorBuild a cURL command from method, URL, headers and body, and get equivalent JavaScript fetch and Python requests code.API Request TesterSend GET, POST, PUT and DELETE requests with headers and body, and view the status, headers and response.SQL Query BuilderBuild SQL queries visually: SELECT with filters and sorting, INSERT, UPDATE, DELETE and CREATE TABLE.Animated Button GeneratorDesign animated CSS buttons with hover effects like glow, slide, pulse and shine, and copy the code.Loading Spinner GeneratorGenerate pure CSS loading spinners and loaders (ring, dots, bars, pulse) with custom color, size and speed.Image Hover Effect GeneratorCreate image hover effects like zoom, grayscale-to-color and caption overlay reveal, and copy the CSS.Image Slider GeneratorGenerate a lightweight, responsive image slider with arrows, dots and autoplay. No jQuery.Click Fireworks Effect GeneratorGenerate a small script that shows a colorful particle burst wherever visitors click on your page.URL ParserSplit any URL into protocol, host, port, path, query parameters and hash, and edit the query string.JSON to TypeScriptPaste JSON and generate TypeScript interfaces with nested types, arrays and optional fields.What Is My BrowserSee your browser, operating system, screen resolution, viewport, pixel ratio, language, time zone and supported features.HTTP Status CodesSearchable list of HTTP status codes with plain-English explanations and SEO notes for 301, 302, 404 and 410.HTML to Markdown ConverterConvert HTML into clean Markdown for README files, docs, blogs and note apps.HTML Table GeneratorPaste CSV, Excel or tab-separated data and get a clean, styled HTML table, or edit cells directly.String Escape / UnescapeEscape or unescape text for JSON strings, JavaScript, HTML, XML, SQL, CSV and regular expressions.IP Subnet Calculator (CIDR)Calculate network address, broadcast, usable host range, netmask and number of hosts for any IPv4 CIDR.
No tools match your search.
Format & validateJSON, XML, YAML, SQL and more.
Encode & decodeBase64, URL, JWT, HTML entities.
PrivateCode and tokens never leave your device.
API & MCPMany tools are also in our developer API.
Frequently asked questions
Quick answers about our developer tools.
Is it safe to paste tokens or API keys?
Developer tools run in your browser, so pasted data is not sent anywhere. As a habit, avoid pasting live production secrets into any website.
Does the JWT decoder verify signatures?
No. It decodes the header and payload so you can read them. Use the JWT Encoder with your secret to create signed test tokens.
Can I use these tools from code?
Yes. Several tools are available through our REST API and MCP server. See the developers page.
Do the formatters change my data?
No. They only change spacing and layout; values stay the same.