Best Way to Compress Images for a Faster Website
A slow-loading page is often just a handful of oversized images. Here's how to fix that without images looking noticeably worse.
A common cause of a slow-loading page turns out to be embarrassingly simple: a handful of images that were never resized or compressed before being uploaded, often several times larger than the space they're actually displayed in on the page.
Why images dominate page weight
A photo straight off a modern phone or camera is routinely several megabytes - far larger than it needs to be for web display, where it's typically shown at a fraction of its original resolution. That gap between original file size and what's actually needed on screen is almost pure waste from a page-speed perspective.
The two-step fix: resize, then compress
- Resize each image down to the actual dimensions it'll display at on the page - there's no benefit to serving a 4000px-wide image into a 800px-wide layout slot.
- Compress the resized images - most of the remaining reduction happens here without a visible quality difference at normal viewing size.
- Spot-check a few images at their actual display size after compressing, not zoomed in, since minor compression artifacts are far more visible zoomed in than they are at normal size.
Choosing a format for web images
WebP generally produces smaller files than JPG or PNG at comparable visual quality, and is well-supported by modern browsers, making it a reasonable default for new web images. PNG is still the right call for images that need transparency or sharp, flat graphics like logos and icons, where JPG-style compression tends to introduce visible artifacts.
How much compression is too much
The goal is the smallest file size that still looks clean at the size it's actually displayed on the page - not the smallest file size possible. Pushing compression aggressively past that point introduces visible blockiness or blurring that undermines the point of having good images on the site in the first place.
Frequently asked questions
How much does image size actually affect page load speed?
Significantly, in most cases - images are typically the largest portion of a page's total download weight, so an oversized, uncompressed image is often the single biggest thing slowing a page down.
Does image compression affect search rankings?
Page speed is one of many factors search engines consider, and compressing oversized images is one of the more reliable ways to improve it without any downside - it's a reasonable, low-risk optimization regardless of how much weight you think ranking factors deserve.
Should I compress images before or after resizing them to their display dimensions?
Resize first, then compress - shrinking a large image down to its actual display size does most of the file-size reduction on its own, and compressing on top of that gets the rest without needing an aggressive quality setting.