These days I'm working exclusively on Total Validator. This checks websites are accessible, have no broken links or spelling mistakes, and adhere to HTML and CSS standards to ensure they work with all modern browsers and accessibility aids. This helps them meet regulations, makes sites easier for all visitors to use, and can improve a website's ranking.
Just enter the home page of a website and it will crawl through it testing all the pages, even password-protected and javascript generated pages. It runs on Windows, macOS and Linux, and there are Chrome, Edge and Firefox add-ons to make it easy to use.
This is a labour of love to help make the Internet accessible for all. Prices are kept deliberately low to make it affordable, starting at less than $15 for the Basic version.
If you are here looking for any of my old Firefox bookmarks add-ons (SyncPlaces, SortPlaces, CheckPlaces or SearchPlaces) then I'm sad to inform you that these are no longer available.
*This is a reference to what the dolphins said to the humans just before the humans were wiped out. From my favourite book: HHGG