Ahrefs is an online toolset utilised for search engine optimisation (SEO) and competitor analysis, which permits users to analyse their website's performance, track keyword rankings, identify backlink opportunities, and research competitors' websites, among other features.
HTTP Strict Transport Security (HSTS) informs browsers that the site should only be accessed using HTTPS.
Vercel is a cloud platform for static frontends and serverless functions.
YouTube is a video sharing service where users can create their own profile, upload videos, watch, like and comment on other videos.