Subdomain rules

When you publish, Layout puts your app at <subdomain>.layout-app.com. The subdomain has to pass a few validation rules before the publish goes through. This is the reference for what those rules are so you can pick a name that works on the first try.

The rules

A subdomain must be:

• Between 3 and 63 characters
• Lowercase letters, digits, and hyphens only — no uppercase, no underscores, no dots
• Not starting or ending with a hyphen
• Without consecutive hyphens — my--app is rejected
• Not a reserved name (list below)

If the name fails any of these checks, the publish panel shows an error and will not let you continue.

Reserved names

These subdomains are blocked because Layout uses them for its own infrastructure:

www       api       app       admin
mail      blog      staging   dev
test      cdn       static    assets
status    docs      help      support
dashboard

Trying to publish at any of these returns the error "This subdomain is reserved and cannot be used".

Examples

Valid:

my-todo
project42
shop-demo
team-dashboard-v2

Invalid:

My-App        → uppercase is not allowed
my_app        → underscores are not allowed
-myapp        → cannot start with a hyphen
my--app       → no consecutive hyphens
ab            → must be at least 3 characters
dashboard     → reserved name

Changing the subdomain later

You can rename a published subdomain at any time — the same rules apply. See Publishing your app for the flow.

Related