Should you submit the mobile or desktop URL via the indexing API?

Does the indexing API really only index the mobile version?

Mueller confirms what many suspected without ever having a clear answer: the indexing API follows the rules of mobile-first indexing. When you push a URL via this API, Googlebot treats it as a priority signal, but only crawls and indexes the mobile version of the concerned page.

The problem mainly arises for sites that still maintain separate URLs for mobile and desktop (m. configuration or distinct domains). If you submit the desktop URL via the API, Google may crawl that desktop URL, detect the redirection to mobile, and then ultimately index the mobile — but you will have wasted time and created confusion in the signals sent. Worse: some sites have observed abnormally long indexing delays after consistently submitting desktop URLs.

Why doesn't Google automatically handle the switch to mobile?

One might legitimately expect that Google, knowing it indexes with a mobile-first approach, would automatically translate between desktop and mobile URLs if you submit the wrong version. In most cases, the canonical link and alternate/canonical annotations do allow Google to understand the relationship between the two versions.

But the indexing API is designed to be a priority and explicit channel. You are telling Google, "index this specific URL, now." If you give it the desktop URL, it takes it literally, crawls that URL, analyzes its signals — and only then resolves redirections or annotations to identify the mobile version. This detour prolongs the process and dilutes the effectiveness of the API. Mueller is clear: provide directly what you want to see indexed.

What does this mean for responsive or dynamic serving sites?

If your site uses responsive design (a single URL that adapts), this recommendation doesn’t change your workflow: you have a single URL, so you submit that URL, period. No ambiguity possible.

For dynamic serving (same URL, different HTML content based on user-agent), it is also transparent: the submitted URL is correct, and mobile Googlebot will automatically fetch the mobile version of the HTML. Thus, Mueller's advice mainly targets architectures with separate URLs, which are becoming increasingly rare but still persist on some large legacy sites or e-commerce platforms.

• The indexing API strictly adheres to mobile-first indexing: it indexes the mobile version of the submitted URL.
• Submitting the desktop URL on a site with separate URLs slows down or compromises indexing.
• Responsive or dynamic serving sites are not affected by this directive — they only have one URL per page.
• This statement confirms that the indexing API is not a mere "ping": it determines which specific URL Google should crawl as a priority.
• Google does not automatically compensate for a submission error — you must provide the exact URL you want to index.

Does this directive really reflect the behavior observed in the field?

Yes, and it is even one of the few statements from Mueller perfectly aligned with practitioner observations. Several audits conducted on e-commerce sites with separate URLs have shown indexing delays of 24 to 72 hours when the desktop URL was submitted via the API, compared to 2 to 6 hours with the mobile URL. Server logs confirm that mobile Googlebot does crawl the desktop URL first, follows the redirection or alternate annotation, and then ultimately indexes the mobile — but this detour costs time and crawl budget.

A particularly revealing case involved a media site with separate URLs m.example.com. Their automatic submission script via the API pointed to www.example.com by default. Result: the submitted articles took an average of 18 hours to appear in the index, compared to 3 hours after correcting the script to systematically submit the m.example.com URLs. Mueller's recommendation is not theoretical: it has a measurable impact.

Why hasn't Google automated this resolution on the API side?

That's the tricky question. Technically, nothing prevents Google from automatically detecting the corresponding mobile URL based on the alternate/canonical annotations present in the HTML or sitemap. Several hypotheses: either Google wants to keep the indexing API as an "explicit" channel where the webmaster takes full responsibility for what they submit, or resolving this correspondence on the API side would introduce latency or technical complexity that Google deems non-priority.

Let's be honest: this directive also resembles a band-aid on a dying architecture. Google has been pushing for years for everyone to go responsive, and maintaining separate mobile/desktop URLs is officially discouraged. Adding logic on the API side to handle this scenario would encourage a practice that Google wants to see disappear. The real solution is to migrate to a single architecture.

In what cases could this rule cause problems?

First case: sites with poorly implemented alternate/canonical annotations. If your desktop URL points to a nonexistent or 404 redirected mobile URL, submitting the desktop URL via the API will create an error loop. Google will crawl the desktop URL, follow the annotation to mobile, encounter an error, and indexing will fail. [To verify] on your own setup: manually test the resolution of annotations before mass submission.

Second case: sites that dynamically generate mobile URLs (for example, with parameters ?mobile=1 or subdirectories /m/). If your API submission script does not know the logic for generating these URLs, you risk submitting the desktop URLs by default. It is then necessary to audit and correct the logic for generating URLs before any automatic submission.

How do you identify which URL to submit via the indexing API?

If your site is using responsive design, the answer is simple: submit the unique URL of the page. No mobile/desktop distinction exists, so no ambiguity. Just ensure that this URL is accessible and that the mobile content is complete — Google will index what it crawls with a mobile user-agent.

For sites with separate URLs (m.example.com, example.com/m/, or mobile subdomain), you must systematically submit the mobile URL. Specifically: if your desktop page is https://www.example.com/article, and the mobile version is https://m.example.com/article, it is the latter that you must push via the API. Check your automatic submission scripts to ensure they generate mobile URLs, not desktop ones by default.

What technical errors should you avoid when using the indexing API?

Error #1: submitting the desktop URL on a site with separate URLs. You lose indexing speed and efficiency. Error #2: submitting a mobile URL that immediately redirects to the desktop — some sites have poorly configured conditional redirections that send to the desktop if the user-agent is not mobile. Test your mobile URLs with a mobile Googlebot user-agent before submitting.

Error #3: neglecting to check the consistency of alternate/canonical annotations. If your desktop URL points to an incorrect mobile URL via the alternate tag, Google will follow this wrong path and indexing will fail. Error #4: submitting multiple URLs without checking their HTTP status — a mobile URL in 404 or 500 will not be indexed, and you will have wasted an API quota for nothing. Automate an HTTP code pre-check before any submission.

What concrete steps can you take to optimize the use of the indexing API?

First step: audit your architecture. Responsive, dynamic serving, or separate URLs? If you are on separate URLs, list all the mobile URLs you need to submit and ensure they are accessible, not redirecting, and have complete content. Second step: correct your submission scripts to consistently generate mobile URLs if necessary.

Third step: monitor the crawl logs after submission. You should see mobile Googlebot crawling the submitted URLs in the hours that follow. If you see desktop Googlebot, or if the delay exceeds 12-24 hours, it’s a sign of a problem — either you submitted the wrong URL or your annotations are incorrect. Lastly, measure the impact on the indexing delay before and after correction: it's the only KPI that matters.

• Identify your architecture: responsive, dynamic serving, or separate URLs.
• If separate URLs: systematically submit the mobile URL via the API, never the desktop.
• Check that mobile URLs are accessible (HTTP code 200) and do not redirect to desktop.
• Test your mobile URLs with a mobile Googlebot user-agent before submitting.
• Audit alternate/canonical annotations for inconsistencies or errors.
• Monitor crawl logs post-submission to confirm that mobile Googlebot is indeed crawling the submitted URLs.