Is the inspection free?
Yes, and there is no signup. Enter a URL, get the findings. There is a rate limit of fifteen inspections an hour per visitor, which exists to keep the server from being used as a scanner, not to push anyone toward a paid tier.
Using The Inspection
Answer it for your own page
The inspection is free, needs no account, and takes a few seconds. It reports what is actually wrong with a page rather than what is generally true about pages.