---
lastModified: 2026-09-10
title: "Domain input needs correction"
description: "That doesn't look like a domain. Try something like yourbrand.com."
---
**Exact messages**

- That doesn't look like a domain. Try something like yourbrand.com.

- Please enter a valid domain

- Domain name is required

- New domain name is required

- Old domain name is required

- Your domain needs at least 8 characters before the dot.

- Domain prefix must be at least 8 characters long

- Domain prefix can only contain letters, numbers, hyphens, and underscores

- Domain prefix must contain at least one letter

- Domain prefix cannot contain forbidden word: \{word\}

- Domain prefix cannot use restricted word: \{word\}

- Domain prefix contains inappropriate language: \{word\}

- You cannot use .runnerai.dev or .runnerai.com domains

- That domain is already in use. Try another.

- Domain is already in use

**Meaning:** The entered domain or Runner-hosted domain prefix does not satisfy the form's rules, or that name is already assigned. Prefix rules are for the prefix field, not a reason to rewrite an unrelated custom domain.

Enter the domain in the format the field requests, such as `yourbrand.com`. For prefix errors, follow the stated length/character requirements and choose a different name for restricted or occupied names. If a domain belongs to another one of your stores, inspect its existing assignment rather than repeatedly adding it.

**Success:** The field is accepted and the intended domain appears on the correct store. Adding a domain is not proof that DNS and HTTPS are ready. Escalate an apparently incorrect ownership/in-use result with the domain and both store identifiers.

[All preview, publishing, and domain errors](/en/guides/help-and-reference/error-playbook-build)