Elfz.io allows you to white label pages from websites like Notion along with features like forms, live chat, notion website custom domain, custom code, and more.
Cloak.ist - Connect any webpage to your custom domain, remove branding and add your own, add custom social meta tags, CSS, and Javascript.
Shorten.REST - A URL shortener API you can depend on
servr - Enrich your app by serving custom domains
PixelMe - URL shortener for savvy marketers
Ethereum URL Shortener - Write URLs to Blockchain forever ⛓
Pixela - Record and Track your habits or effort. All by API.