Don’t get stung :-) Here are some of my favourite tools for web perf and analytics:
Uptimerobot.com - Free tier. 50 monitors. Sends a request every 5 minutes to a website.
Pingdom.com - Free tier. Gives average response times.
Builtwith.com - eg is this a wordpress site, what webserver etc..
Broken Link Checking
Deadlinkchecker.com This handles redirects well
Sitechecker.pro/tool/crawl-report/ - Chrome plugin too
XML Sitemap Generator
https://www.xml-sitemaps.com/ 500 free page limit
https://pro-sitemaps.com/ The pro version of above
https://developers.google.com/search/docs/advanced/sitemaps/overview - What is a sitemap?
Command line tools
Apache benchmarks load testing from the command line
YSlow for testing webpages as a browser plugin
Webpagetest.org - scores on perf, compression, caching, CDN
SSL Labs I found an incomplete SSL Cert security chain using
OWASP Zed Attach Proxy (ZAP) pen testing tool for finding vulnerabilities in web apps. I’ve only briefly used this and it pointed to the same issues as SecurityHeaders.com above.
Lighthouse Chrome extension - this is included in Chrome devceloper extensions now (2021)
Domains and Registration
tld-list.com shows where to get cheap domain names
Cloudflare (not for .co.uk yet) as they charge wholesale if you move domain to them