Stencil, srcset and your upload
Themes call image helpers that request widths. Those helpers cannot invent a smaller *original*. A WebP original at the right width is the cheapest fix that does not require a paid app.
Why it matters
- CSV imports often point at huge manufacturer JPEGs.
- Apps that 'optimise images' add another monthly bill.
- Headless BigCommerce storefronts still fetch those assets.
How to do it
- Pull images from the export or supplier pack.
- Bulk convert to WebP, max width 1600, quality 80.
- Re-import or replace in the image manager. Keep alt text.
Settings that work
Product 1600 px / 80%. Swatch 200 px / 85%. Category banner 1920 px / 75%.