Image compression

Silktide loads your pages in a real browser and identifies photographic images that could be compressed further without visible quality loss. Each image is reported with its current size and the saving that better compression would give.

Why this matters

An under-compressed photograph can be several times larger than it needs to be while looking identical to the eye. The usual cause is images uploaded straight from a camera or design tool into a that doesn't optimise them - one upload, and every visitor downloads megabytes they didn't need, on every page the image appears. Slow pages lose visitors and feed into search ranking through .

Compression is close to free performance: done correctly, nothing visible changes.

How to fix it

Re-export the reported images with sensible compression. For JPEGs, around 85% quality is the widely used sweet spot - large savings, no visible difference.
Automate it. Most can optimise images on upload, and can optimise on delivery, which fixes future uploads too.
While you are re-exporting, consider a modern format for a bigger saving - see Modern image formats.

How Silktide tests this

Load the page in a real browser and collect the JPEG and BMP images it displays.
Compare each image's size against the same image compressed at 85% JPEG quality.
Report images where the saving is meaningful (at least 4 KB), with the current size and the percentage wasted, largest first.

Troubleshooting

How does this differ from the other image checks?

This check estimates savings from JPEG compression during a page load. The separate Image optimisation check goes deeper: it downloads your images and actually re-compresses them with format-specific techniques (including PNG, SVG, and GIF), reporting measured rather than estimated savings. Modern image formats covers converting to WebP or AVIF, and Responsive images covers serving images at the displayed size. The same image can appear in several - the fixes are complementary.

The image is already compressed

The comparison is against 85% JPEG quality. Images exported at higher quality settings, or containing embedded metadata, can still show savings even though they went through "compression" once.