1. Appspector: A great tool to see what a website is built with and what technology it has. 2. Canonical: Great tool for checking the canonical urls 3. Redirect Path: Really useful to see if there are any forms of redirects. 4. META SEO Inspector: Overall SEO inspector 5. BuiltWith: Useful tool to see what software a company is using, great for when you're investigating a potential new client.