11 new free tools for checking websites, DNS and email

Check a site from 3 locations, see if a DNS change has propagated, find out if your mail server is blacklisted, test TLS and IPv6, find broken links and more. Free, no sign-up.

October 12, 2026 · 4 min read · By the Spot Downtime team

When something breaks, the first job is working out what broke: the site, the network, DNS, the certificate or email. We've added 11 free tools for exactly those questions. They need no sign-up, every result has its own link you can share with a colleague, and each one explains what it found in plain English.

Here they are, grouped by the problem they solve.

“Is it down, or is it just me?”

A site that works for you can be down for customers in another country, and the other way round. A CDN location, a network route or a firewall that blocks some regions can all cause outages that only part of the world sees.

Check a website from 3 locationsStatus and response time from California, Amsterdam and Singapore at the same moment.Online ping testIs the server answering at all? Packet loss and round-trip times, with three pings from the internet.

“I changed DNS and nothing happened”

DNS changes don't reach everyone at once. Resolvers keep the old answer until its TTL (time to live) runs out, so for a while some people see the new record and some the old one. Before changing anything else, check whether the change has simply not arrived yet.

DNS propagation checkerWhat 12 public resolvers (Google, Cloudflare, Quad9, OpenDNS and more) return for A, AAAA, CNAME, MX, NS or TXT records, with the ones that differ highlighted.IPv6 readiness testWhether your website, www, name servers and mail servers have IPv6 addresses, and whether the site really answers over IPv6.

“Our email is going to spam”

Missing SPF, DKIM or DMARC records are the most common cause, and our SPF, DKIM & DMARC checker covers those. The next suspect is a blocklist: if the address your mail is sent from has been listed, many providers reject or filter it.

Email blacklist checkerYour domain and its mail servers' addresses against Spamhaus, SpamCop, Barracuda, PSBL, SURBL and more.MTA-STS, TLS-RPT & BIMI checkerThe newer records that force mail to you to travel encrypted, report delivery problems and show your logo in inboxes, including whether your MTA-STS policy actually covers your mail servers.

“Is the site secure and in good shape?”

Browsers stopped supporting TLS 1.0 and 1.1 in 2020, yet plenty of servers still accept them. Broken links quietly cost you visitors and search ranking. Both are easy to miss and easy to fix once you know.

TLS version & HTTP/2 checkerWhich TLS versions a server accepts, the cipher it picks, whether HTTP/2 is on and whether the certificate is trusted.Broken link checkerEvery link and image on a page, with broken ones first and redirects you could tidy up.

Planning and paperwork

Three calculators that run entirely in your browser:

Downtime cost calculatorWhat an outage costs in lost sales and work time, per minute, per hour and per year at different uptime levels. Useful when you need to justify spending on reliability.Subnet & CIDR calculatorNetwork, broadcast, usable host range and masks for any IPv4 or IPv6 prefix.Cron expression generatorPick a schedule and get the cron expression, explained in plain English with the next run times.

Checking by hand only tells you about right now

Every one of these answers a question at one moment. To hear about the next outage, expired certificate or DNS change before your customers do, Spot Downtime checks your sites, APIs, DNS records and cron jobs around the clock, confirms failures from three regions, and alerts you in Slack, Teams, email and more. The Free plan covers your whole team.

All 27 free tools are on the free tools page.