Should you favor a subdomain or a subdirectory for hosting your AMP pages?

Why does Google remain neutral on the URL structure of AMP pages?

Google does not want to impose a rigid architectural constraint for AMP implementation. This flexibility aims to facilitate the adoption of the technology regardless of the technical constraints of an existing site.

Mueller's statement falls within a logic of technical pragmatism: whether you opt for amp.example.com, example.com/amp/ or example.com/page?amp=1, the search engine will treat the pages equivalently. No structure has a crawl or indexing advantage.

What are the practical differences between these three structures?

The subdomain (amp.example.com) requires a separate SSL certificate and dedicated DNS configuration. This option may complicate maintenance but offers a clear technical separation between standard content and AMP.

The subdirectory (example.com/amp/) shares the SSL certificate of the main domain and simplifies analytics management. It is often the preferred choice for its ease of implementation and architectural consistency.

URL parameters (example.com/page?amp=1) allow serving both versions from the same address. This approach reduces apparent duplication but can pose canonicalization issues if misconfigured.

Does the lack of preference really mean total SEO equivalence?

On paper, yes. Google treats these three structures without apparent favoritism for the indexing of the AMP pages themselves. The displayed neutrality reflects a desire to not penalize architectural choices.

That said, some structures may have indirect implications. A subdomain can potentially dilute the authority of the main domain, while a subdirectory concentrates ranking signals on a single root domain. These effects are not specific to AMP but inherent in any multi-version architecture.

• Total flexibility: Google accepts subdomains, subdirectories, and URL parameters without distinction
• No crawl advantage: all three structures are treated equally by Googlebot
• Choice guided by technical criteria: prioritize the structure that simplifies your maintenance and infrastructure
• Be mindful of canonicalization: regardless of the structure, rel=canonical and rel=amphtml tags must be correctly implemented
• Possible indirect impact: subdomains dilute domain authority, regardless of AMP technology

Is this statement consistent with field observations?

Yes, broadly speaking. Sites using different structures for their AMP pages do not show significant performance differences in search results. A/B tests conducted on migrations from subdomain to subdirectory (or vice versa) reveal no measurable impact on organic positions.

That said, this neutrality does not mean that all structures are equal in practice. A misconfigured subdomain (expired SSL certificate, blocking robots.txt, slow DNS) will penalize your AMP pages. Mueller's statement presupposes a flawless technical implementation, which is not always the case on the ground.

What hidden risks are associated with each structure?

Subdomains pose authority fragmentation issues. Backlinks pointing to amp.example.com do not directly strengthen example.com, even if Google understands the relationship between the two. For low-authority sites, this dilution can have a measurable impact.

URL parameters create complications with analytics and tracking tools. Many scripts see ?amp=1 as a session parameter and can fragment traffic data. Without specific configuration in Google Analytics, you risk double counting your visits.

Subdirectories have fewer technical pitfalls but impose a longer URL structure. If your site already uses deep paths (/category/subcategory/article/), adding /amp/ can create URLs exceeding 100 characters, which degrades user experience when shared.

In what cases does this neutrality not truly apply?

Mueller's statement concerns pure indexing. It does not take into account the architectural side effects that can impact your overall SEO. An AMP subdomain not referenced in your main sitemap, with no internal links from the root domain, will be crawled less frequently.

For international sites, managing hreflang becomes significantly more complex with AMP subdomains. You need to declare the language relationships between amp.example.fr, amp.example.de AND example.fr, example.de, which multiplies the risk of configuration errors. [To be verified]: the actual impact of these complex configurations on crawl budget has never been publicly quantified by Google.

What structure should you choose for a new AMP deployment?

If you're starting from scratch, the subdirectory remains the safest choice. It simplifies SSL management, concentrates authority on a single domain, and facilitates analytics tracking without exotic configurations. Opt for a structure like /amp/ or /accelerated/ depending on your semantic preferences.

Subdomains are only justified in two specific cases: when your infrastructure requires a strict technical separation (dedicated servers, different CDN), or when you are testing AMP on a limited part of the site without impacting production. In these situations, the maintenance overhead is compensated by operational flexibility.

URL parameters work if you serve AMP and HTML dynamically from the same code. This approach suits highly application-driven sites (dating sites, SaaS platforms) but complicates CDN caching and requires advanced analytics configuration.

How to migrate between structures without losing traffic?

A migration of AMP structure follows the same rules as a classic migration. Implement permanent 301 redirects from the old structure to the new, maintaining page-to-page correspondence.

Simultaneously update all rel=amphtml tags on your canonical pages and the rel=canonical on your AMP pages. A discrepancy between redirects and relational tags creates an inconsistency that Google may take weeks to resolve.

Submit both sitemaps (old and new) via Search Console for at least two complete crawl cycles. Monitor the index coverage report to detect orphan AMP pages or canonicalization errors.

What configuration errors are lurking with each structure?

With a subdomain, the classic error is to not declare ownership of the subdomain in Search Console separately from the main domain. Google treats amp.example.com as a distinct site: without validation, you will not see AMP errors reported.

With subdirectories, a common pitfall concerns the robots.txt file. Some CMSs automatically generate Disallow rules for the /amp/ or /accelerated/ directories, considered as duplicate content to block. Ensure that Googlebot-AMP has full access to your subdirectory.

URL parameters cause issues with cross-canonicalization. If example.com/page and example.com/page?amp=1 both point to example.com/page as canonical, Google may ignore the AMP version. The AMP version must point to the HTML version, not to itself.

• Choose the structure that simplifies your existing technical infrastructure, not the one that seems most SEO-friendly
• Ensure your SSL certificate covers all subdomains if you choose amp.example.com
• Implement rel=amphtml and rel=canonical tags in a bidirectional and consistent manner
• Declare your AMP pages in a dedicated sitemap or a specific section of your main sitemap
• Test your configuration with Google’s AMP testing tool before any large deployment
• Monitor Search Console's index coverage report to detect unindexed AMP pages