https://web.dev/vitals/
LCP:
https://web.dev/optimize-lcp/
- Largely depends on your server config, DNS response time, TTFB, traffic, network latency, caching, GZIP, PHP version etc. etc.
- Can't do much about render blocking JS, it's always been an issue with X-Cart Classic, core JS code can't be moved from the <head>. reBOOT JS appears at the bottom of the page.
- Defer third-party JS if you can.
- Consider using a CDN.
FID:
https://web.dev/optimize-fid/
- Keep your pages lightweight, don't go overboard with too much content.
- Try masonry layouts instead of product switchers, which will use less HTML code.
- ALWAYS optimise and lazyload your images, videos etc.
- Check any off-site/third-party content you may have.
- Disable any unnecessary modules.
- Ensure HTML, CSS & JS are minified.
CLS:
https://web.dev/optimize-cls/
- Check all your images have width and height attributes set, so there's limited 'shifts' in the layout. Use the CSS
aspect-ratio wrappers.
- For non-catalog images, you might want to consider changing other images to
Base64, which will reduce server requests.
- Using lots of carousels can sometimes affect CLS.
- Using standard font stacks instead of Google fonts may help.
I've just added some image tools
here.
I already know your site is pretty 'lean', but I'd be fairly happy with your results so far.
To optimise your store further, you can remove un-used JS and CSS, but to do so, you need to know what you're doing. I can assist on a site-by-site basis (paid help).
Use the browser console > network tab to check for bottlenecks, page size and speed.