Tools for developers
Everyday helpers for building and debugging software, grouped by the job at hand rather than by category. Every tool page says whether anything you paste leaves your device, so check it before you paste an API response, a token or a config file.
Gathered from the Developer, Design, Network, Security, SEO, Text, Data, PDF, Image and Math categories.
JSON, YAML & data formats
27 toolsFor structured data: checking, tidying, querying and converting it.
- JSON Formatter Pretty-print, minify and fix JSON with exact error locations.
- JSON Validator Strict JSON validation with exact error locations and every path listed.
- CSV to JSON Converter Two-way CSV ⇄ JSON with delimiter detection, safe typing and a preview table.
- XML Formatter Pretty-print or minify XML and find syntax errors by line and column.
- Comma Separated List Converter Column to comma list and back — or SQL IN, JSON, Python and CSV — in one paste.
- JSON Viewer & Tree Editor Browse, search and edit big JSON files in a fast tree — and copy any path.
Show all 27 Show fewer JSON, YAML & data formats tools
- Excel to CSV Converter Turn any sheet into clean CSV — every sheet at once, title rows and merged cells fixed.
- JSON ↔ YAML Converter Two-way JSON ⇄ YAML conversion that keeps numbers exact and warns about YAML traps.
- CSV to Excel Converter CSV to .xlsx without losing leading zeros, phone numbers or long IDs.
- HTML / Web Table to CSV & Excel Copy a table from any web page, Word file or Wikipedia article — get clean CSV or Excel.
- YAML Validator & Formatter Find YAML errors by line, catch YAML 1.1 traps, check Compose and Actions files, format.
- CSV to SQL Converter Typed CREATE TABLE and batched INSERTs, upserts or bulk-load scripts for six databases.
- Excel to JSON Converter Spreadsheet rows to clean, typed JSON — header row as keys, dates as ISO 8601.
- XML ↔ JSON Converter Two-way XML ⇄ JSON with control over attributes, arrays and namespaces — XXE-safe.
- JSON Schema Validator Check JSON against a schema and get every error with its path, line and a clear fix.
- JSON to Excel Converter API responses and nested JSON to a clean Excel workbook — one sheet per list.
- Table Converter Paste a table in any common format, tidy it in a grid, export it in 29 formats.
- JSON Diff & Compare Structural JSON compare with JSON Patch and Merge Patch export — and apply patches too.
- Number Extractor Paste any text and get every number in it, with an exact sum, average, low and high.
- Spreadsheet Format Converter (XLS, XLSX, ODS, Numbers) Change a workbook’s format — and see exactly what carries over before you convert.
- TOML ↔ JSON Converter Exact TOML ⇄ JSON / YAML conversion, with errors that name the rule and the line.
- XSD Validator Check XML against an XML Schema and get every error with its line, path and a clear fix.
- JSON Schema Generator Paste JSON samples and get a JSON Schema that accepts them, ready to refine.
- JSONPath & JMESPath Tester Standard JSONPath and AWS-style JMESPath queries, evaluated live on your JSON.
- JSON Repair Tool Turns almost-JSON into valid JSON — and shows exactly what it changed.
- Text to PDF Converter Plain text, logs and code to a clean PDF — with headers, page and line numbers.
- Excel to PDF Converter (XLSX, CSV) Spreadsheets to print-ready PDFs — formatting, page setup and header rows kept. Pro tool
Format, convert & run code
26 toolsFor making code readable, moving it between languages and trying it out.
- SQL Formatter Readable, consistently indented SQL for 20 dialects — or a safe one-line copy.
- HTML Formatter Indent messy markup cleanly, or minify it without breaking pre, textarea or scripts.
- CSS Formatter Pretty-print CSS for reading, or minify it for production — without breaking it.
- JavaScript Formatter Turn minified or messy JavaScript into readable, consistently indented code.
- JSON to TypeScript Paste JSON, get TypeScript types (and a Zod schema) that fit every sample.
- Markdown Editor Write Markdown and see it formatted as you type — kept in your browser, never uploaded.
Show all 26 Show fewer Format, convert & run code tools
- Markdown to HTML Markdown (or BBCode) in, clean and safe HTML out — with a live preview.
- JSON to Go Struct Paste JSON, get Go structs with json tags that unmarshal it.
- HTML, CSS & JS Playground (Online Editor) A CodePen-style editor with live preview and console — private, sandboxed, no sign-up. Pro tool
- JSON to C# Class Paste JSON, get C# classes with the right serializer attributes.
- JavaScript & TypeScript Online Compiler Write, run and debug JS or TS snippets — safely sandboxed, nothing to install.
- JSON to Java Class (POJO) Paste JSON, get Java classes (one file each) that Jackson can read.
- cURL to Code Converter Paste a curl command, get the same request in your language.
- Python Online Compiler Real CPython in your browser — with stdin, files and a stop button.
- JavaScript Minifier Shrink JavaScript for production with Terser, in your browser, with a source map.
- SQLite Online (SQL Playground) A full SQLite database in your browser — open, query, import, export. Pro tool
- Word to HTML Converter Paste from Word or Google Docs, or open a .docx — get clean, semantic HTML or Markdown.
- JSON to Code Generator Paste JSON, get model classes for Python, Kotlin, Swift, Dart, Rust and 19 more.
- CSS Toolkit Four everyday CSS jobs in one place: specificity, validation, media queries and variables.
- HTML to JSX Converter Paste HTML or SVG, get React JSX that renders exactly the same.
- JavaScript Obfuscator Make JavaScript hard to read: renamed names, encoded strings, flattened control flow.
- CSS Flexbox Generator & Playground Try every flexbox property on live boxes, understand the result and copy the code.
- Docker Run to Docker Compose Converter Paste docker run commands, get a Compose file — or turn a Compose file into commands.
- HTML to PDF Converter HTML code, a saved web page or a ZIP of one — to a PDF, safely and privately. Pro tool
- HTML to Markdown Converter Paste HTML or formatted text and get clean, GitHub-ready Markdown.
- Code Formatter (TypeScript, Vue, Markdown & more) Prettier for 18 languages — auto-detected, configurable, with a diff of every change.
Encode, decode & hash
23 toolsFor encodings, tokens and fingerprints of data.
- Base64 Encoder & Decoder Text and files to Base64 and back — UTF-8 safe, URL-safe, data URIs.
- URL Encoder & Decoder Percent-encode and decode safely, and see every part of a URL.
- JWT Decoder Read any JWT and check its signature — without sending the token anywhere.
- Hash Generator Hashes and HMACs of text or huge files, plus checksum verification.
- Encrypt / Decrypt Text (AES-256) Password-protect a message, send it anywhere, decrypt it here — even offline.
- SSL Certificate Decoder Paste a certificate, a chain or a CSR: every field decoded, every problem explained.
Show all 23 Show fewer Encode, decode & hash tools
- File Encryption & Decryption Lock any file with a password — big files too — and unlock it on any device.
- Text to Binary & Hex Converter See the exact bytes behind any text, and turn binary or hex dumps back into text.
- URL Extractor Every link in a page’s source or any text — cleaned up, counted and filterable.
- Bcrypt Hash Generator & Verifier Create and verify bcrypt hashes in your browser, with timing and the 72-byte check.
- HTML Entity Encoder & Decoder Escape text for HTML, or decode &, © and → exactly as a browser would.
- HMAC Generator Keyed hashes for API and webhook signatures — compute, verify and get the code.
- PGP Encrypt / Decrypt OpenPGP encryption, decryption, signatures and key details — nothing leaves your device.
- Argon2 Hash Generator & Verifier Argon2id hashes with OWASP and RFC 9106 settings, made and checked on your device.
- Encoding Toolkit (All-in-one) Every encoding side by side — paste anything and it works out how to decode it.
- JWT Encoder & Signer Sign a JWT with any standard algorithm — the key never leaves this page.
- Unicode Character Inspector Paste text to see each character — and the invisible or look-alike ones hiding in it.
- AES Encryption Tool (Developer) AES-GCM, CBC and CTR with raw keys, for test vectors and interoperability debugging.
- Password-Protected ZIP Creator AES-256 encrypted ZIP archives made and opened on your device.
- String Escape / Unescape Escape text for 11 languages and formats, or turn escapes back into text.
- Text Encoding Converter & Mojibake Fixer Read old text files correctly, save them as UTF-8, and un-garble “café”.
- CRC Calculator (CRC-8/16/32/64) Every catalogued CRC, custom parameters, checksums and C code — for text, hex or files.
- Image to C Array (Arduino Displays) Images as C arrays for OLED, e-paper and TFT screens, with a byte-exact preview.
Test & debug
24 toolsFor trying patterns, requests and responses before they reach your code.
- Regex Tester Live matches, capture groups and replace preview — safe from runaway patterns.
- Text Diff See what changed between two versions — by line, word or character.
- Security Headers Checker Grade a site’s security headers A+ to F and get copy-paste fixes for your server.
- LLM Token Counter Exact token counts for OpenAI and open models — your text never leaves the browser.
- User Agent Parser See which browser, OS, device or bot sent a request: one user agent or a whole log.
- HTTP Status Codes Reference Every HTTP status code explained: what it means, why you got it and how to fix it.
Show all 24 Show fewer Test & debug tools
- Schema Markup Validator Find syntax errors, schema.org mistakes and missing Google properties in your markup.
- Suspicious Link Checker See where a link really goes, and the tricks it uses, without opening it.
- Redirect Checker Follow a URL hop by hop and see what every redirect does.
- Color Contrast Checker (WCAG 2.2) Test text and background colors against WCAG 2.2, then fix them in one click.
- Find and Replace Text Many find-and-replace rules at once, with regex, case options and highlighted changes.
- HTTP Header Checker See what a server sends back, and what each header means for search.
- Website Down Checker Down for everyone or just you? One check from Cloudflare, one from your browser.
- Broken Link Checker Check every link on a page and see which are broken, blocked or redirected.
- JavaScript Keycode Finder Press a key: get its key, code and keyCode, plus listener code ready to paste.
- REST API Tester (Online API Client) A Postman-style API client in this tab — requests go straight from you to the API. Pro tool
- URL Expander Find out where a short link really goes — without clicking it.
- Robots.txt URL Tester See which crawlers may fetch a URL — and the exact rule that decides it.
- Card & Check-digit Validator Is the number well formed? Luhn, GS1 and ISBN check digits, worked out step by step.
- Link Extractor Every link on a page, with its anchor text and rel values — ready to filter and export.
- OpenAPI / Swagger Editor & Validator Paste an API description: see every problem by line, the API reference and curl commands.
- HAR File Analyzer & Sanitizer See what a page loaded and why it was slow — then clean the file before sending it.
- Hex Viewer & File Inspector A private hex viewer for files of any size, with a data inspector and file-type detection.
- WebSocket & SSE Tester An online WebSocket and event-stream client — straight from your browser to your server.
Keys, tokens & web security
16 toolsFor keys, credentials and how a site defends itself.
- Content Security Policy (CSP) Generator Build a strict, working CSP with hashes, reporting and ready-to-paste server config.
- Password Strength Checker How long would your password survive an attack? Find out without it leaving your device.
- CSR Generator A key and a CSR for your SSL certificate, made on your device — the key never leaves it.
- Passphrase Generator (Diceware) Memorable random passphrases from the EFF word lists — or from your own dice.
- Pwned Password Checker See if a password has leaked in a data breach — without sending the password.
- RSA Key Pair Generator RSA key pairs in every format — PEM, JWK, SSH — made in your browser, self-tested.
Show all 16 Show fewer Keys, tokens & web security tools
- API Key & Secret Generator Cryptographically random API keys and framework secrets, made only on your device.
- SPF Record Checker Find out which servers may send mail for a domain — and why yours might fail.
- DMARC Record Checker See what receivers do with mail that fails DMARC — and how to get to reject.
- Password Protect PDF Lock a PDF with a password and choose what others may print, copy or change. Pro tool
- PGP Key Generator Your own PGP key pair, with revocation certificate, made privately in your browser.
- DKIM Record Checker Is your DKIM key published, strong enough and usable? Check any selector.
- Unlock PDF (Remove a Password You Know) Type the password once and save a copy of the PDF that opens without it. Pro tool
- TOTP / HOTP Code Generator Live 2FA codes from a secret, setup QR codes and authenticator backups, on your device.
- .htpasswd Generator Password lines and config for Apache and nginx Basic authentication, made on your device.
- Elliptic Curve Key Generator (ECDSA / Ed25519 / X25519) EC key pairs in PEM, JWK, raw hex and OpenSSH formats, generated in your browser.
DNS, IPs & certificates
18 toolsFor domains, addresses and certificates.
- DNS Lookup Every DNS record type, straight from Cloudflare or Google, explained in plain words.
- IP Address Lookup Who holds an IP address, which network routes it, and what it is used for.
- What Is My IP Address Your public IP address — IPv4 and IPv6 — and what it tells websites about you.
- DNS Propagation Checker Is your new DNS record visible yet? Compare public resolvers and locations at once.
- Email Header Analyzer Trace where an email came from, and whether it is really from its sender.
- MAC Address Lookup Who made a network device — and whether its MAC address is real, random or multicast.
Show all 18 Show fewer DNS, IPs & certificates tools
- Website Hosting Checker Who hosts a website, who runs its DNS and who handles its e-mail.
- WHOIS Lookup (RDAP) Registration data for any domain, IP address or AS number, from the official registry.
- Domain Availability Checker Is the name free? Ask DNS and the official registries for many TLDs at once.
- MX Lookup Which servers receive mail for a domain — and can senders actually reach them?
- Subnet Calculator Everything about an IP subnet: network, broadcast, host range, masks and splits.
- SSL Certificate Checker Is HTTPS set up right? Certificate trust, redirects, HSTS, mixed content and CT logs.
- Abuse Contact Finder Who to tell about spam, phishing or attacks — taken from the registries’ own records.
- VLSM Calculator Divide one IPv4 network into right-sized subnets, without overlaps or guesswork.
- IP Range to CIDR Converter Ranges to CIDR, CIDR to ranges, merged lists and exclusions — ready for your firewall.
- Subnet Mask Cheat Sheet Every subnet mask on one page — search it, apply it to an address, print it.
- IP Address Converter Any IP address in every notation — and what the registries say about it.
- Port Number Lookup What runs on a port, what IANA says about it, and whether it should face the internet.
Generators & reference
41 toolsFor identifiers, boilerplate and quick lookups.
- UUID Generator Random v4 and time-ordered v7 UUIDs, in bulk — plus a UUID inspector.
- Password Generator Strong random passwords and passphrases, generated only on your device.
- Timestamp Converter Epoch time ⇄ readable dates in any time zone, with daylight saving handled.
- Color Converter Every color format at once, with WCAG contrast checks, tints and shades.
- Chmod Calculator Work out chmod numbers, symbolic modes and umask results, with warnings for risky modes.
- Code Screenshot Generator Carbon-style code images with VS Code themes — made in your browser.
Show all 41 Show fewer Generators & reference tools
- Tailwind Color Palette Generator (50–950) One brand color in, an 11-step Tailwind shade scale out — with contrast for every shade.
- .gitignore Generator Combine official templates, add your rules, and check any path the way git does.
- HTML Table Generator Spreadsheet-style editing, accessible table markup out — styled, responsive and sortable.
- UI Color Theme Generator (shadcn, Tailwind, Material 3) Brand color in, full light and dark theme out — every text pair checked for contrast.
- CSS Gradient Generator Drag color stops, blend in OKLCH or sRGB, and copy the CSS — or save it as a wallpaper.
- Number Base Converter Binary, octal, decimal, hex and every base to 36 — exact, with the working shown.
- CSS Box Shadow Generator Stack shadow layers visually and copy clean CSS, a Tailwind class or a whole shadow scale.
- CSS Grid Generator Paint named areas, size the tracks and get responsive CSS grid code, HTML or Tailwind.
- Cron Expression Generator & Explainer Write, check and translate cron schedules — and see exactly when they run.
- Markdown Table Generator Spreadsheet-style editing for GitHub Markdown tables, with a live preview.
- Mock Data Generator Design the columns, link the tables, and download up to a million rows of test data. Pro tool
- PX to REM Converter px ⇄ rem, em and every CSS length unit — or convert a whole stylesheet at once.
- Glassmorphism CSS Generator Frosted glass over any background, with a text-contrast check that sees through the blur.
- Background Pattern Generator (CSS & SVG) Fifteen seamless patterns with your colors, size and angle — as CSS, SVG or PNG.
- MIME Type Lookup The right Content-Type for any file — and whether a file really is what its name says.
- Neumorphism (Soft UI) Generator Paired light and dark shadows from one base color, with an honest contrast check.
- PDF to Markdown Converter Turn a PDF into Markdown or HTML — headings, lists, tables, code and pictures included. Pro tool
- CSS Clip-Path Generator Draw a clip-path by dragging points, round its corners and wrap text around it.
- Markdown to PDF Converter Markdown in, a clean, print-ready PDF out — tables, code, footnotes and all.
- SVG Wave & Section Divider Generator Make layered waves, curves, tilts and arrows to divide page sections — copy SVG or CSS.
- NanoID, ULID & Snowflake ID Generator Every popular ID format in bulk — and the creation time inside the ones you already have.
- SVG Blob Generator Generate smooth organic blobs from a seed, fill them, and animate one blob into another.
- CSS Text Shadow Generator Stack text-shadow layers on your own words and font, check contrast, copy CSS or Tailwind.
- Cubic Bezier & CSS Easing Generator Shape an easing curve, watch it race the classics and copy CSS, Tailwind or JavaScript.
- Programmer Calculator (Bitwise) Bitwise maths at a real bit width — with overflow, endianness and every base at once.
- Random String & Code Generator Unique coupon, voucher and invite codes, PINs and test IDs — up to 100,000 at a time.
- CSS Animation & Keyframes Generator Design keyframe animations visually and copy accessible CSS or a Tailwind theme snippet.
- CSS Border Radius Generator Round each corner, or drag eight radii into organic shapes — then copy CSS or Tailwind.
- IEEE 754 Floating-Point Converter See exactly how a number is stored in binary floating point — every bit, every digit.
- Color Temperature (Kelvin) to RGB Converter See what color a light of any temperature is, and how warm or cool a color is.
- SVG Shape Generator (Polygon, Star, Badge) Parametric vector shapes with real rounded corners — as SVG, clip-path or PNG.
- Squircle & Smooth Corner Generator Smooth, continuous corners for icons, cards and buttons — as SVG or CSS.
- Apache .htaccess Generator Pick what your site needs and get a commented .htaccess file, with the modules it needs.
- CSS Loader & Spinner Generator Lightweight loading spinners in one element, accessible and motion-friendly.
- Custom Scrollbar CSS Generator Custom scrollbars that work in every browser, previewed in a scrolling box.
Web, SEO & design helpers
22 toolsFor the markup, styles and images around a web page.
- Favicon Generator favicon.ico, app icons, manifest and HTML tags from a logo or a letter.
- Slug Generator Readable, SEO-friendly URL slugs from any title, one at a time or in bulk.
- Meta Tag Generator Head tags with length checks and a live Google-style result preview.
- Robots.txt Generator & Tester Create, check and test robots.txt rules exactly the way Googlebot reads them.
- XML Sitemap Generator Paste URLs, get a valid sitemap.xml — split automatically above 50,000 URLs.
- Open Graph Generator Social sharing tags with an image check and approximate link previews.
Show all 22 Show fewer Web, SEO & design helpers tools
- Schema Markup Generator Fill in a form, get valid JSON-LD with Google’s required and recommended fields marked.
- Canonical Tag Generator Clean up URLs and get rel="canonical" tags — for one URL or thousands.
- Color Palette Generator Press Space for a new palette, lock the colors you like and export them anywhere.
- Open Graph & Social Preview Checker See how your link looks when shared, and fix the tags that break it.
- SERP Snippet Preview Your title and snippet as a search result — cut where results would cut them.
- Color Wheel & Harmony Finder Move a base color around the wheel and get matching colors for any harmony rule.
- XML Sitemap Validator Check an XML sitemap against the protocol and Google’s rules.
- Color Palette from Image Get the main colors of any photo or logo, with how much of the image each one covers.
- 301 Redirect Generator (.htaccess, Nginx, IIS) Turn old-to-new URL lists into server redirect rules, with chain and loop checks.
- Image Color Picker Click any pixel of a photo, logo or screenshot to get its exact color code.
- SVG Optimizer Shrink SVG icons and illustrations with SVGO — previewed safely, nothing uploaded.
- Color Blindness Simulator Preview images and palettes as people with color vision deficiencies may see them.
- Image to Base64 Converter Inline images as data URIs — optimised first, with snippets ready to paste.
- Mesh & Grainy Gradient Generator Drag color points into soft mesh or aurora gradients, add grain, export CSS or 4K images.
- Open Graph & Social Share Image Generator Link-preview images with auto-fitting text and crop checks for each platform.
- Color Difference (Delta E) Calculator Measure how different two colors are with every common Delta E formula.
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Good to know
- 168 of 197 tools run entirely in your browser. The other 29 explain on their pages what they send and why.
- 156 of 197 keep working without a connection once loaded.
- Nothing to install and no account. 188 of the 197 tools are free to use without a limit; the other 9 are Pro tools, which can be tried free every day, and a pass that unlocks them lifts that daily limit.
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