Web Tool Bench

Web Tool Bench is a collection of 33 free web tools for people who run their own sites and email. The DNS and domain tools cover lookups, WHOIS, SSL certificates and HTTP headers, and the email deliverability checker tests SPF, DKIM, DMARC and MX records and gives an overall score. The SEO tools include an on-page checker, redirect checker, robots.txt tester, sitemap checker, broken link checker and a search snippet preview. Developers get generators and utilities such as .htaccess, robots.txt and meta tag builders, a JSON formatter, and password, hash and UUID tools. For business owners there are calculators for margin, break-even, sales tax, ROI and freelance hourly rates.

Every result comes with an explanation of what it means and what to do next, so the output is useful even if you are not an expert in the subject. There is no sign-up and no query limit.