Checkers & Developer
Validate IBAN and EAN, format and check JSON, test regex, look up DNS, see your IP and screen resolution – fast checking tools right in your browser.
An IBAN validator (ISO 13616 check digits, bank name for German accounts), EU VAT number format checker, EAN, ISBN and Luhn checkers, email syntax checker, JSON formatter, XML/CSV validator, regex tester, Base64 and URL encoder, hash and UUID generator, Unix timestamp converter, DNS lookup, user agent, screen resolution and what is my IP; for web design a box shadow, border radius and CSS gradient generator, an aspect ratio calculator and font pairings from system fonts. Your input stays in your browser.
21 tools
- Aspect Ratio CalculatorCalculate the aspect ratio from width and height (1920 × 1080 = 16:9), find the missing side, decimal value, nearest standard ratio and CSS aspect-ratio.
- Base64 Encode and DecodeEncode and decode Base64 and Base64url with proper UTF-8, plus URL encode/decode (percent-encoding). Clear error messages, runs locally in your browser.
- CSS border radius generatorRound corners with sliders: all corners linked or each on its own, px or %, elliptical 8-value syntax – shortest CSS shorthand, live preview and copy button.
- CSS box shadow generatorBuild CSS box shadows with sliders: multiple layers, offset, blur, spread, color with alpha, inset and presets – live preview and one-click copy of the CSS.
- CSS gradient generatorBuild CSS gradients: linear, radial or conic, as many color stops as you need, angle and fallback color – live preview and CSS ready to copy.
- DNS lookupLook up the DNS records of any domain: A, AAAA, MX, TXT, CNAME, NS, SOA, CAA, SRV and PTR – with TTL, DNSSEC status and explained error codes. Free.
- EAN, GTIN and ISBN ValidatorValidate EAN-8, EAN-13, UPC-A, GTIN-14 and ISBN-10/13 check digits, calculate a missing check digit and convert ISBN-10 to ISBN-13 – free, in your browser.
- Validate Email Address SyntaxCheck one or many email addresses for correct syntax under RFC 5321/5322: lengths, domain labels, international domains (Punycode). Local, nothing sent.
- EU VAT Number Checker (Format and Check Digit)Check the format and check digit of an EU VAT number for all 27 member states and Northern Ireland (XI). Runs locally, with links to VIES for validation.
- Font pairing – heading and body font combinationsFont pairs for headings and body text with live preview, copy-ready CSS and availability on Windows, Mac, iPhone and Android – system fonts only, no web fonts.
- Hash Generator: SHA-256, SHA-512, SHA-1, MD5Calculate SHA-256, SHA-384, SHA-512, SHA-1 and MD5 hashes of text or files and verify checksums – locally in your browser, no upload, free.
- IBAN CheckerValidate any IBAN: mod-97 check digits, length and structure for 89 countries, plus bank and BIC for German IBANs. Runs in your browser – nothing is sent.
- JSON formatter, validator and minifierValidate JSON against RFC 8259 with the exact line, column and a plain-English explanation. Beautify or minify, sort keys, copy. Runs locally in your browser.
- Luhn Check Digit Validator and CalculatorValidate numbers with the Luhn algorithm (mod 10, ISO/IEC 7812-1) or calculate the check digit – format check only, runs locally in your browser.
- Regex TesterTest JavaScript regular expressions live: matches highlighted, capture groups in a table, every part of the pattern explained. Free, nothing uploaded.
- Unix timestamp converterConvert a Unix timestamp to a date and back. Seconds, milliseconds, micro- and nanoseconds detected automatically; UTC, local time, ISO 8601 and more.
- UUID generator: create and validate UUID v4 and v7Generate UUIDs online: version 4 (random) or version 7 (time-ordered), up to 1,000 at once. Validate a UUID and decode its version, variant and timestamp.
- What is my IP address?Instantly shows your public IP address, detects IPv4 or IPv6 and explains the difference. Free, no sign-up – your IP address is never stored.
- What is my screen resolution?Instantly see your screen resolution, physical pixels, browser viewport, devicePixelRatio, aspect ratio and CSS breakpoint. Live, right in your browser.
- What is my user agent?See your user agent string and detect browser, version, engine, OS and device type, plus User-Agent Client Hints. Parse any other UA too. Runs locally.
- XML and CSV validator onlineCheck XML for well-formedness and validate CSV against RFC 4180: errors with line and column, auto-detected delimiter, table preview. Runs locally.