What to Avoid

These items create avoidable performance regressions on Marketplace sites.

Uploading unoptimized images, including full-resolution DSLR photos.
Omitting mobile-specific hero images, which forces mobile devices to download desktop assets.
Running an overloaded GTM container with a large number of active tags.
Keeping stale campaign tags and duplicate analytics tools enabled.
Building deeply nested page structures that inflate DOM complexity.
Using autoplay background videos without mobile fallbacks.
Shipping large background videos that exceed the size budget.
Publishing images without alt text.

Large media files increase LCP because the browser has more data to download before the primary content is fully visible.
Deep DOM structures increase parse and render time.
Excess third-party scripts increase on-device work and can degrade responsiveness.