Mobile-First Indexing
Google's practice of using the mobile version of a page's content for indexing and ranking instead of the desktop version. Mobile-first indexing reflects the reality that most searches now occur on mobile devices.
Mobile-first indexing means Google primarily sees your site as a mobile user would. If content, links, or structured data are only present on the desktop version, Google may not see them at all. This fundamentally changes how you should think about building web pages: mobile is the primary experience, and desktop is the enhancement.
For engineering teams, mobile-first indexing requires ensuring feature and content parity between mobile and desktop experiences. Use responsive design rather than separate mobile URLs. Ensure all content, images, and structured data are present and fully functional on mobile. Verify that robot meta tags and canonical tags are consistent across device types. Check that lazy-loaded content is accessible without user interaction (Google's crawler does limited scrolling). Test your mobile experience with Google's Mobile-Friendly Test and the URL Inspection tool in Search Console. Performance is especially critical on mobile, where network conditions are often slower and devices less powerful than desktop.
Related Terms
Core Web Vitals
A set of three Google-defined metrics that measure real-world user experience for loading performance, interactivity, and visual stability. Core Web Vitals are a confirmed ranking factor in Google Search.
Largest Contentful Paint (LCP)
A Core Web Vital that measures the time from page load start until the largest visible content element (image, video, or text block) is rendered on screen. Good LCP is 2.5 seconds or less.
Interaction to Next Paint (INP)
A Core Web Vital that measures the latency of all user interactions (clicks, taps, keyboard input) throughout the page lifecycle, reporting the worst interaction. Good INP is 200 milliseconds or less.
Cumulative Layout Shift (CLS)
A Core Web Vital that measures the total amount of unexpected layout shifts that occur during a page's entire lifespan. Good CLS is 0.1 or less, where layout shifts are calculated from the impact and distance of moving elements.
Time to First Byte (TTFB)
The duration from the user's request to the first byte of the server response reaching the browser. TTFB measures server-side processing speed and network latency, directly impacting all subsequent loading metrics.
Crawl Budget
The number of pages a search engine bot will crawl on your site within a given timeframe, determined by crawl rate limit and crawl demand. Crawl budget optimization ensures important pages are discovered and indexed efficiently.