Validators and assertions

Shortcut assertion Validator
h1 Allow only one H1
og Required set of Open Graph meta tags
title There must be a title tag and it must be no longer than 55 characters
alt All images must have an alt tag
lang The HTML opening tag should have a valid lang attribute
vp There should be a viewport meta tag with width and initial-scale set
atxt Links should have a descriptive text
auvid No autoplaying videos, they bad for accessibility reasons and really annoying
mdesc There should be a description meta tag with content between 50 and 160 characters
canon It is a good practice to have a canonical link on your pages

If you have an idea for a new validator, be sure to open an issue!