Separate mobile URLs are a mobile setup where desktop and phone visitors receive different HTML at different URLs, usually on a subdomain such as m.example.com (hence “m-dot”). Google names this next to responsive design and dynamic serving.
How does the setup work?
Google’s documentation uses the desktop URL as the canonical and the mobile URL as its alternate. Both versions need matching rel=canonical and rel=alternate annotations, and Google notes that user-agent and Vary headers are used to send users to the right version. Google recommends responsive design instead, because it is the easiest setup to maintain.
Google’s checklist for separate URLs includes:
- error pages return the same status on desktop and mobile
- the mobile version contains no URL fragments
- content is equivalent on both versions
- hreflang links connect mobile URLs to mobile URLs and desktop to desktop
- robots.txt rules work for both versions
- both versions are verified in Search Console
- the mobile server can handle the added crawl load
| Configuration | URL | HTML | Technical signals | Google's position |
|---|---|---|---|---|
| Responsive design | same URL on every device | same HTML; the layout adapts to the screen size | none needed; content and metadata are identical on mobile and desktop | recommended as the easiest pattern to implement and maintain |
| Dynamic serving | same URL on every device | different HTML per device, chosen by user-agent detection | Vary: user-agent response header | supported; the mobile version needs the same content as desktop |
| Separate mobile URLs (this term) | a separate URL per device, e.g. m. | different HTML per device | mobile page: rel="canonical" to the desktop URL; desktop page: rel="alternate" with media to the mobile URL; redirects based on user agent and Vary | supported; the desktop URL is always canonical, and hreflang links mobile to mobile and desktop to desktop |
Google uses the mobile version of a page, crawled with the smartphone agent, for indexing and ranking (mobile-first indexing). Only the content shown on the mobile version is used for indexing. Google's best practices on signals and content parity apply to dynamic serving and separate URLs only; with responsive design, content and metadata are the same anyway. Sources: Google Search Central: Mobile site and mobile-first indexing best practices (last updated 2025-12-10); MDN: Vary header. Last checked: .
Example
On the desktop page:
<link rel="canonical" href="https://www.example.com/page">
<link rel="alternate" media="only screen and (max-width: 640px)" href="https://m.example.com/page">
On the mobile page:
<link rel="canonical" href="https://www.example.com/page">
Common mistakes
- The mobile page shows less content than desktop, although Google indexes the mobile version.
- Error pages return a different status code on the mobile subdomain.
Sources
- Mobile sites and mobile-first indexing – Google Search Centraldevelopers.google.com
- Consolidate duplicate URLs – Google Search Centraldevelopers.google.com
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