Web & developer
Check a site's certificate, look up domains, codes and formats, and fix what you find, with plain-language explanations for developers.
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Utilities
- Browser infoBrowser, engine and device facts, reported here., private, runs on your deviceChecker
- Color contrast checkerCheck the WCAG contrast of text on a background, see which levels it passes, and get a nearby color that does., private, runs on your deviceCheckerColour
- Color converterPick or type any color and copy it as HEX, RGB, HSL, HWB or OKLCH, with its nearest CSS name., private, runs on your deviceConverterColour
- Country codesISO 3166 alpha-2, alpha-3 and numeric codes, calling codes and domains of 249 countries and territories., private, runs on your deviceEverydayReferenceNetworks
- CSS unit converterConvert CSS lengths between px, rem, em, pt, pc, in, cm, mm and Q at your font size., private, runs on your deviceUnit conversionConverterLength
- Data size converterConvert between bytes, kilobytes, megabytes, gigabytes, MiB, GiB and bits, with 1,000 and 1,024 kept apart., private, runs on your deviceUnit conversionConverterEncoding
- DNS lookupLook up addresses, mail servers and other DNS records., private, runs on your deviceCheckerNetworks
- Download time calculatorEnter the file size and your connection speed to see how long a download or upload takes., private, runs on your deviceCalculatorNetworks
- Hash generatorSHA-256, SHA-512, SHA-1 and MD5 hashes of any text, made in your browser., private, runs on your deviceGeneratorEncoding
- HTTP status codesLook up any HTTP status code: what 200, 301, 404, 429 or 503 means, when a server sends it, whether caches keep it and which RFC defines it., private, runs on your deviceReferenceNetworks
- Is it down?Check a website’s response from our server., private, runs on your deviceCheckerNetworks
- JSON formatterPaste JSON to find errors, tidy it up or make it compact., private, runs on your deviceCheckerConverterEncoding
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- Password generatorA random password made on your device, with its strength in bits and nothing sent anywhere., private, runs on your deviceGenerator
- SSL Certificate CheckerExpiry, issuer, covered names, chain and TLS version of any public site, with plain-language fixes., private, runs on your deviceCheckerNetworks
- URL encode and decodePercent-encode text for a web address, or decode %20 and friends back to plain text., private, runs on your deviceConverterEncoding
- UUID generatorRandom UUIDs, version 4 or time-ordered version 7, made on your device., private, runs on your deviceGeneratorEncoding
- What is my IP?Your public IP and the network behind it., private, runs on your deviceCheckerNetworks
- WHOIS lookupFind the registrar, dates and name servers reported by WHOIS., private, runs on your deviceCheckerNetworks
Web checks look at public information only, such as a site's certificate, and explain each finding in plain words with what to fix.
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