PageSpeed Insights says 'properly size images'. How do I fix it?
The audit means the browser downloads far more pixels than the page displays. The fix is to change the file's dimensions, not just to compress it: find the width the image is shown at, resize the file to that width, or twice it for high-density screens, with the ratio lock on, then replace the file on your site.
What the audit actually measures
'Properly size images' compares the dimensions of the image file with the space it takes on the page. A 4032 px phone photo placed in an 800 px column makes every visitor download an image five times wider than needed, and five times taller. Compression makes each pixel cheaper but does not remove the extra pixels, which is why the warning can survive heavy compression.
Step one: find the displayed width
- Open your page in a desktop browser, right-click the image and choose Inspect.
- Hover over the image element in the developer panel; the size it is rendered at appears on screen.
- Try the widest window size you care about, because in a responsive layout the image grows with the screen.
- Note the largest width you saw. That is the number to build on.
Step two: resize the file
A 4032 × 3024 photo displayed 800 px wide.
With the ratio lock on, type 800 as the width and the height becomes 600 on its own.
For sharpness on high-density screens, type 1600 instead, and the height becomes 1200.
In the Image resizer the original dimensions appear as soon as you choose the image. Type the new width with the lock on, pick JPEG or WebP, and check the new file size in the table before downloading. The downloaded name carries the size, such as -800x600, so you will not mix up versions when uploading.
Step three: replace the file and test again
Upload the new file in place of the old one and run the test again. If your theme shows the image at several sizes on phone and desktop, prepare the file for the largest. After resizing, run it through the Image compressor if it is still heavy; the two audits are separate, and one can appear without the other.
Some store platforms create smaller copies of your images themselves, while others serve the file exactly as you uploaded it. If the warning stays on an image you uploaded at the right size, the issue is in how the theme serves it, not in the file, and the theme settings need a look.
Common questions
Should I always use twice the width?
Twice the width helps images where sharpness matters, such as the main product photo. Small images and thumbnails are fine at the displayed width, which keeps them lighter.
Will resizing change how the image looks on the page?
No. With the ratio lock on the proportions stay the same, and the page shows it in the same space.