Two situations each get their own answer:
- The domain on its own - for example
app.example.com with nothing after the slash - A link that does not exist - mistyped, deleted or never created, like
app.example.com/oldcampaign. Longer paths such as app.example.com/product/123 follow the same choice
For each, choose one of:
- Show a not-found page
- Send them to your web address - a page on your own site, such as your homepage
- Send them to a default Onelink - one of your Onelinks, so visitors still reach the right app store
Set this under
Settings > Custom Domains, in the domain's
When no Onelink matches section. Add the web address or choose the default Onelink first: a choice can only name a destination the domain has.
When a link that does not exist goes to your web address, you also decide what happens to the path: drop it, let it replace the web address's path, or add it to that path - so
app.example.com/product/123 can land on the matching page of your site.
The web address must be a full
http or
https URL and cannot point back to the same custom domain. Links that match one of your Onelinks always go to that Onelink's destinations.