Splitting a website into two separate versions (Desktop vs. Mobile) is an outdated practice that creates a high risk of AI indexing errors. The standard for AI readiness is Responsive Web Design. This uses a single website code base and identical content that dynamically adjusts its layout to fit any screen size. This ensures AI crawlers and human visitors always see the exact same information. To help you audit your current setup for AI compliance, let me know: Does your website currently use a separate mobile URL (like yoursite.com), or does it use a responsive layout that changes automatically? Are you noticing a drop in search visibility or AI tool references on one specific device type? You said: where i am coming from is this: the classic website created in weebly or wordpress for example will automatically reformat for the small screens. the proble with that is the result may not be an optimized one - slow downloads, excessive scrolling, too many images, poorly placed phone numbers and calls to action etc. the way to overcome this is to insert html coding for nre mobile version which appeats in response to the instruction 'if screen< 480px then...' it is not an unrelated or seperate site, just a replacement set of instructions That approach makes perfect sense, and you have pinpointed the exact trap of "lazy" automatic responsiveness. Simply stacking a massive desktop layout into a single, mile-long mobile column creates a frustrating user experience. Using conditional code—like CSS media queries (@media (max-width: 480px)) or JavaScript to serve a streamlined mobile layout—is a smart way to fix this for humans. When it comes to AI, this method works well, but only if it is executed carefully. Here is exactly how AI is influenced by this specific technique: 1. AI Evaluates Your Code, Not Just the Visual Render AI crawlers do not just look at the screen; they read the underlying source code. The "Hidden Content" Trap: If you use display: none; in your CSS to hide heavy desktop sections on mobile, the text is still technically in the HTML code. Some AI crawlers will still read it, but search engine AIs might penalize the site if they think you are trying to "stuff" keywords into hidden text. The Best Practice: Instead of hiding desktop elements, use modern layout tools like CSS Grid or Flexbox to reorder elements (e.g., pulling the phone number to the very top on mobile) and use lightweight, responsive image attributes (srcset) so mobile users don't download heavy desktop files. 2. Core Web Vitals and AI Performance Scores AI algorithms track how fast your mobile instructions execute. If your custom mobile code forces the browser to download the heavy desktop assets anyway before hiding them, your page speed scores will drop. AI engines will interpret this high load time as a low-quality user experience and may rank your site lower in AI-driven search results. 3. Google's Mobile-First Bot is Your Primary Judge Because Google and other AI-driven engines crawl using a simulated smartphone screen (usually 360px to 411px wide), they will only execute and evaluate the instructions inside your < 480px code block.