Free tools
Check a website in seconds
Quick answers when something looks wrong: is it down, is it slow, is the certificate valid, where does the domain point and why is email landing in spam. Free, no sign-up.
Website
- Website down checkerFind out if a website is down for everyone or just you, with the status code and response time.
- Website speed testTime each step of loading a page: DNS, connection, TLS, server response and download.
- SSL certificate checkerSee who issued a site's certificate, when it expires, which names it covers and whether it's trusted.
- Security headers gradeGet an A+ to F grade for a site's HTTPS and security headers, with what to fix.
- HTTP headers & redirect checkerFollow every redirect hop and see the response headers, including which security headers are set.
- robots.txt & sitemap checkerRead a site's robots.txt rules, find its sitemap and count the pages in it.
Domain & DNS
Network
- IP & reverse DNS lookupFind the hostname of an IP address and which network and organisation it belongs to.
- Open port checkerCheck whether a TCP port such as 22, 443 or 3306 is open on a server, from the internet.
- What's my IP address?See your public IP address and the country it appears to come from.
Calculators & reference
- Uptime & SLA calculatorTurn an uptime percentage like 99.9% into allowed downtime per day, month and year, and back.
- Cron expression explainerTranslate a cron schedule like */5 * * * * into plain English and see its next run times.
- HTTP status codesWhat every HTTP status code means, why it happens and how to fix it, from 200 to 526.