Why is my Shopify store fast on desktop but slow on mobile?

Mobile is tested on a throttled connection and a weaker CPU, so the same page that flies on your laptop struggles on a mid-range phone. The usual offenders: oversized images downloaded at full desktop resolution, JavaScript from apps that has to parse on a slower processor, and a large hero/banner that delays the largest contentful paint.

Fix it by serving correctly-sized responsive images, deferring non-critical scripts, and trimming what loads above the fold on mobile specifically. Google ranks on mobile, so this is the version that actually matters for SEO.