Why does my site still feel slow after I compressed the images?

Often you compressed the right images but shipped them at the wrong dimensions, or you skipped format. A 2000-pixel hero shown at 600 pixels wastes bytes twice: you keep huge pixels and then the browser downscales them. Fix size, then format, then look again.

What is the fastest image format for a website in 2026?

Next-gen formats are mandatory now: WebP for universal support and AVIF where browsers accept it. For photos you can also use a responsive set (srcset) so a phone gets a small file and a desktop gets a sharp one. Serve whichever the browser supports.

Should every image on my site be lazy-loaded?

Be selective. Lazy-load anything below the fold and in carousels, but keep the first, most important image above the fold eager so it paints instantly. Lazy-loading everything can actually hurt your LCP by delaying the hero.

Your Website Is Still Slow: The Image Check

You ran the speed test, got a red flag on images, compressed a few, and... it still feels slow. Sound familiar? That is because squeezing file size alone fixes only one layer of the problem. Past the number, three separate things all count.

1. Size the file to the slot

A banner displayed at 600 pixels wide never needs to ship as a 4000-pixel file. The browser downloads all those pixels, then throws most away. Re-export to the display width first — this alone often beats any quality fiddling. Adding a responsive srcset lets phones grab a small file and desktops a sharp one.

2. Pick the right format

For photos on modern browsers, WebP beats JPEG at the same quality, and AVIF goes further on browsers that accept it. Graphics and logos stay crisp as SVG or a lean PNG. Serving several candidates and letting the browser choose costs nothing and captures most of the win.

3. Compress, then verify

Only after sizing and format should you touch the quality bar. On photos, quality 80 strips redundant data with no visible change — see the quality-80 method. Drop legal limits and decorative backgrounds lower.

4. Lazy-load the right half

Below-the-fold images and carousels should lazy-load so they don't block the first paint. But keep the hero image eager — lazy-loading it makes the largest paint slowest, the exact opposite of what you want.

Run the loop

Compress every upload locally with the compressor, including a WebP pass.
Re-test; if images still top the list, check dimensions and srcset next.
Measure, change one thing, measure again. Chasing all threads at once hides which fix moved the needle.