Using a branded domain on your links
Assign a verified domain to a link, Bio Links page, or Smart Pick.
Once a domain shows Verified, you can pick it (instead of the shared golo.to) when creating or editing a link, your Bio Links page, or a Smart Pick page.
Slugs are per-domain
The same slug can exist once on golo.to and separately again on each of your own domains - they don't share one namespace. See Slugs and link expiration.
Multiple domains
You can connect more than one domain and choose which one each link uses individually - there's no single "default" domain setting beyond the shared golo.to; the domain field just remembers whichever one you picked most recently as a convenience.
Changing a link's domain later
Editing which domain a link uses works like any other link edit - the old short URL on the previous domain stops working once you change it, so update anywhere you've already shared that link.
Related articles
Adding a custom domain - Type it into Settings - then complete DNS setup and verification.
Choosing a custom slug - Slugs are unique per domain, not shared across all of them.
Connecting a custom domain - Add your domain and verify it with DNS records.
Creating a branded link - Pick your verified domain when creating the link.