Reducing size without visible loss.
WHAT COMPRESSION DOES
Removes data the eye does not notice.
A well-compressed photograph is frequently a fifth of the original size and looks identical.
HOW TO DO IT
Free online compression tools Image editors, which let you choose quality when saving Plugins that compress on upload
WHAT QUALITY SETTING TO USE
For photographs, around 80 per cent is usually indistinguishable from the original.
Below about 60 you start to see it.
WHAT TO CHECK
Look at the compressed image at full size before publishing.
Compression artefacts show worst in skies, gradients and fine detail.
FOR EXISTING SITES
Plugins can compress your existing library in bulk.
Back up first. Compression is not reversible.
THE ORDER THAT WORKS
Resize first, then compress.
Compressing an oversized image still leaves an oversized image.
WHAT THIS ACHIEVES
Frequently a page several times lighter, with no visible difference.
