How to compress images for a website
Updated
Heavy images are the single most common reason web pages feel slow. Here is how to make them light without making them look worse.
Why image weight matters
On most websites images are the largest thing the browser has to download, often more than the code and fonts combined. Every extra hundred kilobytes pushes back the moment the page becomes usable, and that delay is exactly what Google measures as Largest Contentful Paint, one of the Core Web Vitals that affect ranking.
Lighter images also mean lower bounce rates on mobile, where connections are slower and data costs money. Compressing images is usually the highest-impact, lowest-effort performance win available to a site owner.
How much should you compress
The goal is the smallest file that still looks identical to the eye, not the smallest file possible. Aggressive compression that introduces visible blur or banding hurts trust and conversions more than a slightly larger file ever would.
Compresso handles this automatically: it compresses, then compares the result with the original pixel by pixel and keeps the smaller version only when the difference is imperceptible. Typical savings are 50 to 80 percent for PNG and around 70 percent for JPEG with no visible change.
Which format to use
Use JPEG for photographs, PNG for logos, icons and anything with transparency, and WebP when you want the best balance of size and quality for the modern web. WebP is supported by every current browser and is usually 25 to 35 percent smaller than the equivalent JPEG.
If you are unsure, compress in the original format first. Converting to WebP is a separate optimization you can layer on later once the basics are in place.
A fast workflow
Drop all the images for a page onto the compressor at once, let it process them, then download everything as a single ZIP. Replace the originals in your project, commit, and redeploy. For a typical page this takes a couple of minutes and can cut total image weight by more than half.
Re-run this whenever you add new images. The discipline of compressing before committing keeps a site fast as it grows, instead of letting weight creep back in over months.