Mobile Performance Drag
Mobile-first indexing means Google ranks you on the mobile rendering of every page. When a popular URL scores 80 on desktop and 35 on mobile, you're being ranked on the 35. This report surfaces those URLs — weighted by clicks so the worst offenders rise to the top.
Why it matters
Most teams optimise to the desktop PSI score because that's what shows up in dev tools and CI. But that's the score nobody is being ranked on. A wide mobile-vs-desktop gap on a high-traffic URL is a silent ranking dampener that classical PSI dashboards don't surface.
How it's built
- For every URL with both a mobile and a desktop PSI run, compute
desktop_score − mobile_score. - Keep only URLs where that gap is at least 20 points (a meaningful divergence — < 20 is within normal noise between profiles).
- Multiply the gap by the URL's 28-day clicks to get the Drag Score.
- Pair that with the site-wide GSC mobile-vs-desktop average position gap — the macro signal confirming whether the per-URL drag is showing up in actual ranking outcomes.
How to read the tiers
- Severe drag (≥ 40 pt gap) — almost certainly a mobile-only render-blocking asset, oversized hero image, or third-party script that mobile profiles down-rank harder than desktop.
- Moderate drag (20–39 pt) — usually fixable with image format / lazy-load tweaks. Not a fire, but worth queueing before the next core update.
- Site mobile-pos vs desktop — the GSC angle. Positive numbers mean your mobile rankings are systematically worse than desktop, which usually means the per-URL drags are translating into real ranking pain.
Limitations
The site-wide position gap is at the device level, not query × URL × device. We can't currently
confirm which queries are being dragged on which page, only that the drag exists at the
URL level. Per-query mobile drag would require ingesting gsc_query_device_day, which
isn't part of the current schema.
Data requirements
- PSI runs on both
mobileanddesktopstrategies for the same URL. - GSC
gsc_page_dayfor clicks, andgsc_device_dayfor the site-wide gap.