Free Developer Tools
Everyday utilities for developers: format and validate JSON, convert between JSON, CSV, XML and YAML, beautify HTML, CSS, JavaScript and SQL, decode JWTs, test regular expressions and more.
All processing happens client-side, so it's safe to paste config files, API responses and tokens. Nothing leaves your machine.
61 free tools · No sign-up · Works on phones and computers
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Popular developer tools
- JSON FormatterBeautify, minify and validate JSON, with clear error locations.
- JSON to CSV ConverterTurn a JSON array into a CSV spreadsheet you can open in Excel.
- Base64 Encoder & DecoderEncode text to Base64 or decode Base64 back to text (UTF-8 safe).
- Unix Timestamp ConverterConvert Unix timestamps to dates and dates to timestamps.
- Regex TesterTest regular expressions with live match highlighting and groups.
All developer tools
Grouped by what they help you do.
61 tools
- JSON FormatterPopularBeautify, minify and validate JSON, with clear error locations.
- JSON ValidatorCheck if JSON is valid and see exactly which line and character is wrong.
- JSONPath Tester & FinderQuery JSON with JSONPath expressions and filters, and click any value to get its path.
- JSON Schema GeneratorGenerate a JSON Schema (draft 2020-12) from sample JSON, with formats and required fields detected.
- JSON to CSV ConverterPopularTurn a JSON array into a CSV spreadsheet you can open in Excel.
- CSV to JSON ConverterConvert CSV or spreadsheet data into a clean JSON array.
- JSON to XML ConverterConvert JSON into well-formed, indented XML.
- XML to JSON ConverterConvert XML documents into readable JSON, attributes included.
- YAML to JSON ConverterConvert YAML to JSON and validate YAML syntax.
- JSON to YAML ConverterConvert JSON into clean, readable YAML.
- JSON to TypeScriptGenerate TypeScript interfaces from a sample JSON object.
- JSON to C# ClassesGenerate C# classes or records from sample JSON, with JsonPropertyName attributes.
- JSON to SQL ConverterTurn JSON into CREATE TABLE and INSERT statements for Postgres, MySQL, SQLite or SQL Server.
- CSV Viewer & FormatterView CSV as a sortable, searchable table and re-save it with any delimiter.
- HTML to JSX ConverterTurn HTML into React JSX: className, htmlFor, style objects, self-closing tags and SVG props.
- HTML to Markdown ConverterConvert HTML to clean GitHub-flavoured Markdown — headings, lists, links, code blocks and tables.
- TOML to JSON ConverterConvert TOML config files to JSON and back, with clear line-numbered errors.
- YAML to CSV ConverterTurn a YAML list into a spreadsheet-ready CSV, with nested keys flattened into columns.
- Markdown Table GeneratorBuild Markdown tables in a grid, or paste from Excel, Sheets or CSV — with column alignment.
- XML FormatterPretty-print and validate XML with proper indentation.
- HTML FormatterBeautify or minify HTML markup.
- CSS Formatter & MinifierBeautify messy CSS or minify it for production.
- JavaScript FormatterBeautify minified or messy JavaScript so it's readable again.
- SQL FormatterFormat SQL queries with consistent indentation and keyword case.
- YAML Formatter & ValidatorFormat, validate and tidy YAML with consistent indentation — comments kept.
- CSS Specificity CalculatorScore CSS selectors (IDs, classes, elements), rank them and see which rule wins.
- CSS Units ConverterConvert between px, rem, em, %, vw, vh, pt, cm and more using your own base sizes.
- Base64 Encoder & DecoderPopularEncode text to Base64 or decode Base64 back to text (UTF-8 safe).
- HTML Entity EncoderEscape special characters as HTML entities, or decode them back.
- JWT DecoderRead a JSON Web Token's header and payload, and check its expiry.
- JWT GeneratorCreate and sign HS256, HS384 or HS512 JSON Web Tokens for testing.
- Punycode Converter (IDN)Convert international domain names to Punycode (xn--) and back, and spot look-alike domains.
- HTML Entities ReferenceSearch HTML entities and special characters — arrows, maths, currency, quotes — and copy the code.
- UUID GeneratorGenerate random UUIDs (v4 or time-ordered v7) in bulk, and validate them.
- Unix Timestamp ConverterPopularConvert Unix timestamps to dates and dates to timestamps.
- Regex TesterPopularTest regular expressions with live match highlighting and groups.
- Cron Expression ParserExplain a cron schedule in plain English and list its next run times.
- Number Base ConverterConvert between binary, octal, decimal and hexadecimal.
- Markdown to HTMLConvert Markdown to HTML with a safe live preview.
- Chmod CalculatorWork out Linux file permissions in numeric and symbolic form.
- HTTP Status CodesEvery HTTP status code explained in plain English, searchable.
- Mock Data GeneratorGenerate fake test data — names, emails, numbers, dates — as JSON, CSV or SQL.
- Regex ExplainerBreak a regular expression into plain-English pieces you can understand.
- User Agent ParserDetect the browser, version, OS and device type from any user agent string.
- Hex ViewerInspect any file byte by byte: hex and ASCII side by side, magic-number detection and search.
- Bitwise CalculatorAND, OR, XOR, NOT and shifts in 8 to 64 bits, with decimal, hex and binary side by side.
- .env File Editor & ValidatorCheck .env files for duplicates and mistakes, and convert them to JSON, YAML, Docker or Kubernetes.
- .gitignore GeneratorCombine .gitignore templates for languages, frameworks, editors and operating systems.
- Docker Compose GeneratorBuild a docker-compose.yml with Postgres, MySQL, Redis, Nginx and more.
- Git Command HelperFind the right git command for what you want to do — undo, branch, stash and more.
- IP Subnet & CIDR CalculatorNetwork, broadcast, host range and mask for any IPv4 CIDR — and split into subnets.
- Dockerfile GeneratorCreate a production Dockerfile and .dockerignore for Node, Next.js, Python, Go, Java or static sites.
- GitHub Actions Workflow GeneratorBuild a CI workflow YAML: test matrix, caching, lint/test/build steps and optional deploy.
- README GeneratorWrite a polished README.md with badges, features, install steps, usage and license.
- Changelog GeneratorTurn commit messages into a Keep a Changelog entry grouped into Added, Fixed, Changed…
- Commit Message GeneratorWrite Conventional Commits messages with type, scope, body, breaking changes and issue links.
- package.json GeneratorCreate a valid package.json with scripts, dependencies, engines and npm name checks.
- .htaccess GeneratorGenerate Apache .htaccess rules: HTTPS, www, redirects, caching, gzip, security headers and SPA routing.
- Cookie Consent Banner GeneratorCreate a lightweight, accessible cookie banner (HTML, CSS, JS) with accept, reject and categories.
- Mock API Response GeneratorDesign a fake API response and get MSW, Express or Vitest mock code with status, headers and delay.
- HTTP Request BuilderBuild an HTTP request and get it as cURL, fetch, Axios, Python requests or HTTPie code.
Good to know
Formatting vs validating
A formatter makes valid data easier to read by adding indentation and line breaks. A validator tells you whether data is valid at all and, if not, exactly where the problem is. The JSON formatter does both: it formats valid input and points to the line and column of the first error otherwise.
Developer guides
Step-by-step help that goes with these tools.
- Guide · DeveloperHow to Format JSON Correctly (and Fix the Errors That Break It)What valid JSON looks like, how to pretty-print and minify it, and how to fix the eight errors that cause most “Unexpected token” messages.Oct 4, 2026 · 8 min read
- Guide · DeveloperHow to Convert CSV to JSON (and Back) Without Breaking Your DataConvert spreadsheet data to JSON and JSON back to CSV correctly: quoted commas, line breaks inside cells, numbers vs text, nested objects and Excel quirks.Oct 4, 2026 · 7 min read
- Guide · DeveloperWhat Is a Unix Timestamp? Epoch Time ExplainedWhat Unix time is, why it starts in 1970, how to tell seconds from milliseconds, how time zones fit in, and how to convert timestamps in common languages.Oct 4, 2026 · 6 min read
Developer tools: common questions
Is it safe to paste tokens and secrets?
The tools run entirely in your browser and make no network requests with your data. Even so, treat production secrets carefully and rotate any you have shared anywhere.
Do you execute my code?
No. Formatters parse and re-print code; they never run it. The regex tester runs your pattern in an isolated worker with a time limit.
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