Developer Tools
Free developer tools — JSON formatter, Base64, URL and HTML encoders, UUID and hash generators, JWT decoder, regex tester, CSS generators and more.
JSON Formatter & ValidatorFormat, validate and minify JSON online. Pretty-print with 2 or 4 spaces, see exact error line and column, copy or download the result.Base64 Encoder / DecoderEncode text or files to Base64 and decode Base64 back — UTF-8 safe, with data URI output and file download. 100% in your browser.URL Encoder / DecoderURL-encode and decode text live in both directions. Choose encodeURIComponent for values or encodeURI for full URLs. Free and private.HTML Entity Encoder / DecoderEncode special characters to HTML entities and decode named or numeric entities back to text — live, free and fully in-browser.UUID GeneratorGenerate 1 to 1000 random version-4 UUIDs instantly. Options for uppercase and no-hyphen formats, with one-click copy of the full list.Hash Generator (MD5, SHA-1, SHA-256, SHA-512)Generate MD5, SHA-1, SHA-256 and SHA-512 hashes from text or files instantly — all four at once, computed locally in your browser.JWT DecoderDecode JWT tokens instantly — view header and payload as pretty JSON, check expiry with human-readable dates. 100% local, nothing uploaded.Regex TesterTest regular expressions live with highlighted matches, capture groups, match positions and flags — plus ready-made patterns for email, URL, IP.Markdown PreviewWrite markdown and see the rendered result live, side by side. Copy the generated HTML or download it as an .html file. Free, no sign-up.CSS Gradient GeneratorCreate linear, radial and conic CSS gradients visually — up to 5 color stops, angle control, live preview and copy-ready CSS code.Box Shadow GeneratorDesign CSS box shadows visually with sliders for offset, blur, spread and opacity. Stack multiple layers, preview live and copy the CSS.Color Converter (HEX, RGB, HSL, CMYK)Convert colors between HEX, RGB, HSL and CMYK instantly. Flexible input, live swatch, and clickable tints and shades of any color.CSS & JS MinifierMinify CSS and JavaScript online — strip comments and whitespace safely, see bytes saved, then copy or download the compressed code.Cron Expression GeneratorBuild cron expressions with dropdowns, get a plain-English explanation and see the next 5 run times. Paste existing crontab lines to decode them.AI Token CounterCount GPT-4o and GPT-4 tokens in your text with real tiktoken encodings, plus words, characters and an API cost estimator.Random API Key GeneratorGenerate secure random API keys online — hex, alphanumeric, base64url, UUID v4 or prefixed formats, up to 100 at once, with entropy shown. Private.Aspect Ratio CalculatorCalculate and simplify aspect ratios (16:9, 4:3), solve missing width or height while keeping proportions, and check common video and social sizes.Chmod CalculatorConvert Linux file permissions between checkboxes, octal (755) and symbolic (rwxr-xr-x) notation — with a ready-to-copy chmod command and reference table.PX to REM ConverterConvert px to rem and rem to px instantly with a custom root font size, a full 1–64px conversion table and CSS best-practice notes.HTML FormatterBeautify and indent messy HTML, or minify it. Choose 2/4 spaces or tabs, preserve script and style blocks, copy or download — all in your browser.IP Subnet CalculatorCalculate network address, broadcast, usable host range, subnet mask and host count from any IPv4 address and CIDR prefix. Free and instant.JSON to TypeScript ConverterGenerate TypeScript interfaces or type aliases from sample JSON. Merges array shapes, marks optional fields, builds unions — instant and private.JavaScript FormatterBeautify and re-indent minified or messy JavaScript. Preserves strings, template literals, comments and regex. Copy or download — fully in-browser.YAML Formatter and ValidatorFormat, validate and minify YAML in your browser. Get precise error line numbers, normalise indentation, or collapse to compact flow style. Private.CSS Border Radius GeneratorDesign border-radius visually with per-corner sliders and a live preview. Link all corners or set each one, then copy ready-to-use CSS. Free.CSV to TSV ConverterConvert CSV to tab-separated values in your browser. Handles quoted fields and embedded commas correctly. Copy or download the TSV — free and private.HTTP Status Code LookupLook up any HTTP status code's meaning, category and common usage. Search by number or keyword across 1xx to 5xx — instant reference for developers.IPv6 Compressor and ExpanderCompress IPv6 to canonical RFC 5952 form or expand it to full notation. Detects address type and shows the binary prefix. Free and in-browser.MAC Address GeneratorGenerate random locally administered MAC addresses in colon, hyphen or Cisco format. Bulk output, upper or lowercase, copy or download. Free.MIME Type LookupFind the correct MIME type for any file extension, or search MIME types by name. Covers images, audio, video, fonts, documents and archives. Free.Nano ID GeneratorGenerate compact, URL-safe Nano IDs with custom length and alphabet. Cryptographically random, unbiased, bulk output. Copy or download — free.TSV to CSV ConverterConvert tab-separated data to CSV with proper RFC 4180 quoting. Choose the output delimiter. Paste straight from Excel or Sheets. Free and private.ULID GeneratorGenerate sortable ULIDs — 26-character time-ordered IDs with 80 bits of randomness. Bulk output, upper or lowercase, decode timestamp. Free.CSV to JSON ConverterConvert CSV rows into JSON objects in your browser. Auto-detects delimiter, uses the header row as keys, and can coerce numbers and booleans. Free.CSV to XML ConverterConvert CSV rows into XML records with custom root and row element names. Escapes special characters and sanitises headers. Copy or download. Free.GraphQL FormatterFormat and validate GraphQL queries, mutations and schemas. Consistent indentation, syntax checking with line numbers, copy or download. In-browser.HMAC GeneratorGenerate HMAC signatures with SHA-256, SHA-1, SHA-384 or SHA-512. Enter a message and secret, get hex and Base64 output. Web Crypto, fully in-browser.JSON to CSV ConverterConvert an array of JSON objects to CSV. Flattens nested objects, unions all keys, escapes fields per RFC 4180. Copy or download. Free and private.JSON to Python Dataclass ConverterGenerate Python dataclasses from sample JSON. Infers types, converts camelCase to snake_case, marks optionals. Modern or typing-module style. Free.SQL FormatterFormat SQL queries with clause line breaks, keyword casing and your choice of dialect and indentation. Handles subqueries and joins. Copy or download.XML Formatter and ValidatorFormat, validate and minify XML in your browser. Native well-formedness checking with error location, clean indentation, CDATA preserved. Free.XPath TesterTest XPath expressions against your XML and see matching nodes, attributes or values instantly. Namespace-aware, uses the browser's XPath engine. Free.Port CheckerUnderstand how to test if a TCP port is open, find your public IP, and use a common-ports reference. Explains why real port checks need a server.Query String ParserParse a URL or query string into a readable table and JSON. Decodes percent-encoding, groups repeated keys into arrays. Copy any value. Free.REM to PX ConverterConvert rem to px and back with a configurable root font size. Live two-way conversion, ready CSS snippet, and a common-values reference table. Free.URL ParserBreak any URL into protocol, host, port, path, query and fragment. Lists decoded query parameters and outputs JSON. Forgiving of missing scheme. Free.DNS LookupFree DNS lookup tool — query A, AAAA, MX, TXT, NS, CNAME and SOA records for any domain instantly, straight from your browser over DNS-over-HTTPS.SSL Certificate CheckerConfirm a site's HTTPS is live and learn to inspect its SSL certificate. Free checker with DNS resolution plus links to trusted SSL analysis tools.WHOIS LookupInvestigate any domain with our free WHOIS helper — resolve its live DNS in-browser and jump to trusted WHOIS services for registrar and ownership data.AES Encrypt & DecryptEncrypt or decrypt text with AES-GCM and a password, entirely in your browser. PBKDF2 key derivation, Base64 output, nothing uploaded.CIDR CalculatorConvert an IPv4 address and CIDR prefix into subnet mask, wildcard, network, broadcast, usable host range and address counts.CSS Flexbox GeneratorBuild Flexbox layouts visually — set direction, justify, align, wrap and gap — with a live preview and copy-ready CSS.CSS Formatter & BeautifierBeautify and minify CSS online — fix indentation, spacing and line breaks, or compress to one line. Fast, private, in-browser.CSS Grid GeneratorBuild CSS Grid layouts visually — set columns, rows, gaps and alignment — with a live preview and copy-ready grid CSS.JSON Diff CheckerCompare two JSON documents structurally and see exactly what was added, removed or changed, with the full path to every difference.JSON Schema GeneratorGenerate a draft-07 JSON Schema from sample JSON automatically — infers types, required fields and nested structures. Copy or download.JSON Schema ValidatorValidate JSON data against a JSON Schema in your browser — checks type, required, properties, items, enum and min/max, with error paths.JSON to C# Class ConverterGenerate C# classes from sample JSON — PascalCase properties, nested classes, List<T> for arrays and nullable types. Copy or download.JSON to Java Class ConverterGenerate Java classes from sample JSON — typed fields with getters and setters, nested classes and List<T> for arrays. Copy or download.JSON to XML ConverterConvert JSON to XML with a configurable root element — nested objects become elements, arrays repeat, and output is neatly indented.JSON to YAML ConverterConvert JSON to clean, readable YAML in your browser — proper indentation, block sequences and safe quoting. Copy or download.JSONPath TesterTest JSONPath expressions against your JSON and see matched values instantly — supports dot/bracket paths, array indexes, wildcards and recursion.JWT GeneratorCreate signed JSON Web Tokens (HS256/384/512) from a header, payload and secret — signed locally with Web Crypto, nothing uploaded.JWT VerifierVerify a JWT's HMAC signature with your secret and inspect its claims — checks HS256/384/512 and flags expiry, all locally in your browser.User Agent ParserParse any user-agent string into browser, engine, operating system and device — or detect your own. Runs entirely in your browser.XML to JSON ConverterConvert XML to JSON in your browser — elements become keys, attributes are preserved, and repeated tags become arrays. Copy or download.YAML to JSON ConverterConvert YAML to JSON in your browser — handles mappings, sequences, nesting and common scalars. Friendly errors, copy or download.CSR DecoderDecode a PEM certificate signing request (CSR) in your browser and read its subject, public key details and signature algorithm.Certificate DecoderDecode an X.509 certificate (PEM) in your browser and read its subject, issuer, validity dates, serial number and public key details.PEM to JWK ConverterConvert a PEM public or private key into a JSON Web Key (JWK) in your browser using Web Crypto. Supports RSA and EC keys.XML to CSV ConverterFlatten repeating XML records into a CSV table — pick the record element and its child fields become columns. Copy or download.Bcrypt Generator & CheckerHash a password with bcrypt at a cost factor you choose, or check a password against an existing bcrypt hash — all in your browser.OpenAPI ValidatorValidate an OpenAPI or Swagger spec (JSON or YAML) in your browser — checks required fields, structure and paths, with a clear summary.RSA Key Pair GeneratorGenerate an RSA public/private key pair (2048/3072/4096-bit) locally with Web Crypto and export both as PEM. Nothing leaves your browser.