{"id":8891,"date":"2026-11-05T13:48:01","date_gmt":"2026-11-05T06:48:01","guid":{"rendered":"https:\/\/adtek.agency\/glossary\/mobile-first-indexing\/"},"modified":"2026-11-05T13:48:01","modified_gmt":"2026-11-05T06:48:01","slug":"mobile-first-indexing","status":"publish","type":"mona_glossary","link":"https:\/\/adtek.agency\/en\/glossary\/mobile-first-indexing\/","title":{"rendered":"Mobile-first indexing"},"content":{"rendered":"<p>Mobile-first indexing means Google uses the mobile version of a site&#8217;s content, crawled with a smartphone agent, for indexing and ranking. Put simply, Google judges a page by what a phone user sees.<\/p>\n<h2>What is mobile-first indexing<\/h2>\n<p>Google started mobile-first crawling and indexing in 2016. On October 31, 2023, Google announced the switch was complete; only a small set of sites that do not work on mobile are still crawled by the desktop Googlebot (<a href=\"https:\/\/developers.google.com\/search\/blog\/2023\/10\/mobile-first-is-here\" target=\"_blank\" rel=\"nofollow noopener\">Google Search Central Blog, Mobile-first indexing has landed, accessed November 2026<\/a>).<\/p>\n<p>Content that exists only on the desktop version is effectively invisible to Google. Google says a mobile page with less content can lose some traffic, and suggests moving content into accordions or tabs instead of cutting it (<a href=\"https:\/\/developers.google.com\/search\/docs\/crawling-indexing\/mobile\/mobile-sites-mobile-first-indexing\" target=\"_blank\" rel=\"nofollow noopener\">Google Search Central, Mobile-first Indexing Best Practices, accessed November 2026<\/a>).<\/p>\n<h2>The viewport tag: what the AIO checker scores<\/h2>\n<p>The viewport meta tag tells mobile browsers to fit the page to the screen width. The standard tag goes in the <code>&lt;head&gt;<\/code>:<\/p>\n<pre><code>&lt;meta name=\"viewport\" content=\"width=device-width, initial-scale=1\"&gt;<\/code><\/pre>\n<p><code>width=device-width<\/code> matches the page to the screen width. <code>initial-scale=1<\/code> sets a 1:1 ratio between CSS pixels and device-independent pixels. Without the tag, mobile browsers lay out the page at a desktop width, usually about 980px, then shrink it (<a href=\"https:\/\/web.dev\/articles\/responsive-web-design-basics\" target=\"_blank\" rel=\"nofollow noopener\">web.dev, Responsive web design basics, accessed November 2026<\/a>).<\/p>\n<p>Hypothetical example: a 390px-wide phone showing a page laid out at 980px shrinks everything to about 40% (390 \/ 980). 16px text becomes roughly 6px, and users have to zoom in to read it.<\/p>\n<p>Adtek&#8217;s <a href=\"\/en\/tools\/ai-search-checker\/\">AIO checker<\/a> gives the &#8220;Mobile viewport&#8221; check 2 points and passes it when the page has a meta viewport tag.<\/p>\n<h2>Mobile-first indexing: what must match on both versions<\/h2>\n<p>Google recommends responsive web design (one URL, a layout that adapts) because it is the easiest pattern to implement and maintain. Sites with a separate mobile version (for example m.example.com) need a closer check (same Best Practices source):<\/p>\n<ul>\n<li>The same main content as desktop, including text, images and video.<\/li>\n<li>The same structured data.<\/li>\n<li>Equivalent title elements and <a href=\"\/en\/glossary\/meta-description\/\">meta descriptions<\/a>.<\/li>\n<li>The same image alt text and the same robots meta tags.<\/li>\n<li>Main content that does not load only after a tap or swipe, and does not appear only after JavaScript runs (see <a href=\"\/en\/glossary\/javascript-seo\/\">JavaScript SEO<\/a>).<\/li>\n<\/ul>\n<h2>Why it matters for AI search<\/h2>\n<p>To be shown as a supporting link in AI Overviews and AI Mode, a page must be indexed and eligible to appear in Google Search with a snippet; Google says there are no additional technical requirements (<a href=\"https:\/\/developers.google.com\/search\/docs\/appearance\/ai-features\" target=\"_blank\" rel=\"nofollow noopener\">Google Search Central, AI features and your website, accessed November 2026<\/a>). Since Google indexes the mobile version, content missing from mobile is also not available to Google&#8217;s AI features. For ChatGPT or Perplexity crawlers, no company has said the viewport is a signal.<\/p>\n<h2>How to add the viewport tag when the checker flags it<\/h2>\n<ol>\n<li><strong>Check.<\/strong> Press Ctrl+U to view the page source and search for &#8220;viewport&#8221;.<\/li>\n<li><strong>WordPress with a block theme<\/strong> (edited in the Site Editor): WordPress has printed the viewport tag itself since version 5.8 through the function <code>_block_template_viewport_meta_tag<\/code> (<a href=\"https:\/\/developer.wordpress.org\/reference\/functions\/_block_template_viewport_meta_tag\/\" target=\"_blank\" rel=\"nofollow noopener\">WordPress Developer Resources, accessed November 2026<\/a>).<\/li>\n<li><strong>WordPress with a classic theme.<\/strong> Modern themes usually include the tag in header.php. If it is missing, use the theme&#8217;s header code field (if it has one), or create a child theme, copy the parent&#8217;s header.php into it and add the tag inside <code>&lt;head&gt;<\/code>, so parent theme updates do not wipe it.<\/li>\n<li><strong>Shopify.<\/strong> The <code>&lt;head&gt;<\/code> lives in the <code>theme.liquid<\/code> layout file (<a href=\"https:\/\/shopify.dev\/docs\/storefronts\/themes\/architecture\/layouts\" target=\"_blank\" rel=\"nofollow noopener\">Shopify Dev, Layouts, accessed November 2026<\/a>). Popular themes usually include the tag already; for a customized theme, add it there.<\/li>\n<li><strong>Custom-built sites.<\/strong> Add the tag to the shared template used by every page.<\/li>\n<li><strong>Check again.<\/strong> Run Lighthouse in Chrome DevTools: the audit &#8220;Has a &lt;meta name=&#8221;viewport&#8221;&gt; tag with width or initial-scale&#8221; should pass; as of Lighthouse 13 it sits inside the &#8220;Optimize viewport for mobile&#8221; insight (<a href=\"https:\/\/developer.chrome.com\/docs\/lighthouse\/pwa\/viewport\" target=\"_blank\" rel=\"nofollow noopener\">Chrome for Developers, Lighthouse viewport audit, accessed November 2026<\/a>). Turn on DevTools device mode to view the page at phone size. URL Inspection in <a href=\"\/en\/glossary\/google-search-console\/\">Google Search Console<\/a> shows whether the page was crawled with a smartphone or desktop agent. Finally, run the AIO checker again.<\/li>\n<\/ol>\n<p>Do not look for the Mobile-Friendly Test. Google retired it, along with the Mobile Usability report, starting December 1, 2023, and pointed to Lighthouse instead (<a href=\"https:\/\/developers.google.com\/search\/blog\/2023\/04\/page-experience-in-search\" target=\"_blank\" rel=\"nofollow noopener\">Google Search Central Blog, Page experience in Search, accessed November 2026<\/a>).<\/p>\n<h2>Frequently asked questions<\/h2>\n<h3>Will a site without a mobile version be dropped from Google?<\/h3>\n<p>No. Google says a mobile version is not required for your content to be included in results. Phone users will just see a shrunken, hard-to-read page.<\/p>\n<h3>Is mobile-first design the same as mobile-first indexing?<\/h3>\n<p>No. Mobile-first design usually means designing for the phone screen first. Mobile-first indexing is how Google indexes pages. Sites designed mobile first tend to have fewer issues when Google reads the mobile version.<\/p>\n<p>If you need a review of your site&#8217;s technical foundation for Google and AI search, see Adtek&#8217;s <a href=\"\/en\/solution\/seo\/\">SEO solution<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Mobile-first indexing means Google uses the mobile version of a site&#8217;s content, crawled with a smartphone agent, for indexing and ranking. Put simply, Google judges a page by what a phone user sees. What is mobile-first indexing Google started mobile-first crawling and indexing in 2016. On October 31, 2023, Google announced the switch was complete; [&hellip;]<\/p>\n","protected":false},"author":4,"featured_media":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_acf_changed":false,"_yoast_wpseo_title":"Mobile-First Indexing: What It Is and the Viewport Tag","_yoast_wpseo_metadesc":"What is mobile-first indexing? 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