Large, uncompressed images are the single most common reason WordPress websites load slowly. This guide covers practical steps to reduce image file sizes without losing visible quality.
Why image size matters
When someone visits your website, their browser downloads every image on the page. A single uncompressed photo from a modern phone can be 5 MB or more. If your homepage has four or five of these, a visitor on a mobile connection could be waiting several seconds just for the images to appear.
Smaller images mean faster page loads, better performance scores, and a better experience for your visitors.
Step 1: Resize images to display dimensions
Before uploading an image to WordPress, check how large it actually appears on your page. If your website displays images at 800 pixels wide, there is no benefit to uploading a 4000 pixel wide original.
You can resize images using any basic image editor. On a Mac, Preview can do this. On Windows, the built-in Photos app works. Online tools are also available if you search for "resize image online."
A good rule of thumb: make the image no wider than 1200 pixels for full-width images, and no wider than 800 pixels for images in a content column.
Step 2: Use WebP format
WebP is a modern image format that produces files 25 to 35 percent smaller than JPEG at the same visual quality. All current browsers support it, including Chrome, Safari, Firefox, and Edge.
Many image editors and online converters can save images as WebP. When saving, a quality setting of 80 to 85 percent gives a good balance between file size and appearance.
Step 3: Compress images before uploading
Image compression reduces file size by removing data that the human eye cannot detect. There are two types:
- Lossless compression reduces file size slightly without any quality change.
- Lossy compression reduces file size more significantly with minimal visible quality loss.
For website images, lossy compression at 80 to 85 percent quality is usually the right choice. The difference is not visible on screen, but the file size can drop by 60 percent or more.
You can compress images using an image optimisation plugin in WordPress. Search for "image optimisation" in the WordPress plugin directory to find options.
Step 4: Let WordPress handle lazy loading
Since WordPress 5.5, images are lazy loaded by default. This means images further down the page are only downloaded when the visitor scrolls near them, rather than all at once when the page first loads.
You do not need to configure this. WordPress adds loading="lazy" to images automatically. This is particularly helpful on pages with many images, such as galleries or portfolios.
What to aim for
As a general target, most website images should be under 200 KB each. Hero images and full-width banners might be 200 to 400 KB. If any image on your site is over 1 MB, it almost certainly needs to be resized or compressed.
Optimising your images is the single most effective thing you can do to improve your website's loading speed.
Frequently asked questions
What is the best image format for websites?
WebP is the best general-purpose format for web images. It produces smaller files than JPEG or PNG with no visible difference in quality. All modern browsers support WebP.
Should I resize images before uploading them to WordPress?
Yes. If your image displays at 800 pixels wide on the page, upload it at roughly that size. Uploading a 4000 pixel wide photo and relying on the browser to shrink it wastes bandwidth and slows down loading.
Does WordPress compress images automatically?
WordPress applies light compression to JPEG images when it creates different thumbnail sizes, but it does not compress the original upload. For best results, compress images before uploading or use an image optimisation plugin.
Last updated: 4 April 2026