How to compress images for WordPress

WordPress will happily accept a 6 MB photo straight from your phone, resize it into six thumbnails, and serve it to every visitor. It will also make your pages crawl. The fix is not a plugin installed on top of a messy media library — it is getting the file right before you upload it.

Start with pixels, not kilobytes

WordPress itself creates the sizes it needs — thumbnail, medium, large and whatever your theme registers. What it cannot do is repair an image that is far too big to begin with, because every one of those generated copies inherits the problem.

So decide the largest size the image will actually be shown at, and upload that:

• Article images — the content column is rarely wider than about 800–900 pixels. Uploading 1280 px gives you room for high-density screens without waste.
• Full-width header or hero — 1600–1920 px. There is almost never a reason to go wider.
• Logo — export at roughly twice the height it is displayed at, so it stays crisp on retina screens. A logo is vector artwork, so a PNG or WebP export works better than a JPEG.
• Product photo — 1600 px on the long edge is a good balance between zoom quality and file size.

Then choose a format and a quality

For photographs, WebP is the sensible default: the same visual quality lands in a substantially smaller file than JPEG, and every browser WordPress has to support on current versions can display it. Keep JPEG for anything that must stay compatible with older external tools, and PNG only when you need transparency or perfectly crisp flat colour — a screenshot of text, for example.

Aim for a final file of roughly 100–250 KB for a photo that fills the content column. If you are far above that, the problem is almost always resolution rather than quality: dropping the quality slider to 40 gets you a blurry mess, while resizing to the right pixel width gets you the same smaller file with no visible damage.

The order that works

1. Work from the original camera or design file.
2. Resize to the largest size the image will be displayed at.
3. Compress the smaller image, keeping the quality around 70–80 for photos.
4. Convert to WebP if the rest of your site is served in WebP too.
5. Check the result on a phone before you upload it.

If you have a folder of images ready to go, the batch tool applies the same settings to all of them and hands back a ZIP, which saves a lot of clicking.

Before you upload: two things that catch people out

Filename. Rename IMG_4821.jpg to something descriptive such as walnut-desk-organiser-side-view.jpg before uploading. WordPress derives the attachment slug from the filename, and descriptive names are one of the few image SEO details you fully control.

Alt text. Alt text is what a screen reader announces and what shows when an image fails to load. Describe the image rather than stuffing in keywords: "walnut desk organiser with two pen cups" beats "desk organiser, pen holder, gift".

If images are still slow after all this

Compression is only half of it. Modern browsers pick a file based on the width attribute of your theme and the reported device width, so the markup matters too. If you are debugging with a page speed tool and the report points at images, compare the reported file size against the dimensions it says are being downloaded: if a 300-pixel thumbnail is being served as a 1600-pixel file, the media library has the wrong version, and re-uploading a correctly sized file is faster than installing another plugin.

Frequently asked questions