Speed: does my site load fast?
Google PageSpeed Insights
The reference. Paste your URL and it returns two scores out of 100: one for mobile, one for desktop. Focus on the mobile score. That’s where most of your visitors land, and it’s almost always the worse of the two.
Free, no account.
GTmetrix
More detailed than PageSpeed: it shows the weight of every image and script, so you can see exactly what’s slowing the page down. Be aware that the free plan has tightened: an account is required, you get 5 tests per month, and mobile testing is paid-only.
The big picture: a single grade
HubSpot Website Grader
A score out of 100 covering performance, SEO, mobile and security. Use it when you want an overall verdict rather than a technical report. One thing to know: it asks for your email address before showing the report, and HubSpot then uses it for sales outreach. Use a secondary address if you’d rather skip the follow-ups.
Security: is my site clean?
Sucuri SiteCheck
Scans your site for malicious code and checks whether Google has blacklisted you. Your first move if something feels off after an update or a hastily installed plugin. Its limit: it only sees what’s visible from the browser, not what happens server-side.
Qualys SSL Labs
Tests your HTTPS certificate, the little padlock, and grades it from A+ to F. Below an A, your host has something to fix. The report is technical, but the grade takes one second to read.
MDN HTTP Observatory
Built by Mozilla. It checks your site’s invisible protections (security headers) and gives you a grade. Same principle: read the grade, pass the details to whoever builds your site.
Google Safe Browsing
It answers one question, but it’s the most serious one: does Google consider your site dangerous? If so, Chrome shows visitors a red warning screen before they ever reach your page. Five seconds to check.
Visibility: can people find me?
Ahrefs Webmaster Tools
Free for sites you can prove you own. It crawls your site and lists the technical problems costing you rankings: broken links, missing titles, orphan pages. It’s the most thorough audit on this list.
Bing Webmaster Tools
Often forgotten, and that’s a mistake: Bing also feeds the answers of several AI assistants. It’s free, and it shows you which keywords you show up for.
Rich Results Test (Google)
Checks whether your page can display rich elements in Google: review stars, prices, Q&As, breadcrumbs. In practice, that’s what makes your link take up more room than your competitor’s.
Behaviour: what do visitors actually do?
Microsoft Clarity
Free, with no traffic limit. It records real visits and builds heatmaps: you see where people click, where they hesitate, and the moment they give up. No other tool on this list tells you why people leave.
Accessibility
WAVE
Flags what makes your site unusable for someone with low vision: weak contrast, images without descriptions, badly labelled forms. These are often ten-minute fixes, and they help your search rankings too.
Uptime
UptimeRobot
The other tools are snapshots. This one watches continuously and emails you the moment your site goes down. Free for up to 50 sites. Because the worst case isn’t a slow site. It’s an offline site nobody told you about.
Where to start
If you only do one thing: PageSpeed Insights, looking at the mobile score. If you do three: add Safe Browsing (five seconds) and install Clarity, which needs a few days of traffic before it becomes useful. The rest can wait.