Optimising Images for Search: Filenames, Alt Text and Speed

Images do far more for SEO than most people realise. Optimised well, they can appear in Google Images, support your page’s relevance, improve accessibility and keep your site fast. Left unoptimised, they are one of the most common causes of slow pages.

The good news is that image optimisation is largely mechanical. A handful of consistent habits — sensible filenames, real alt text, proper compression and the right format — cover most of what matters.

Filenames and alt text

Rename images before uploading so the filename describes the picture — roof-repair-norwich.jpg rather than IMG_4821.jpg. It is a small signal, but it helps Google understand the image and your page.

Alt text describes the image for screen readers and for Google when the image cannot load. Write a genuine, plain description of what is shown. It aids accessibility first and SEO second, and stuffing keywords helps neither.

Size and speed

Oversized images are the usual reason pages load slowly. Resize images to the dimensions they are actually displayed at, then compress them so the file is as small as it can be without looking poor.

Modern formats such as WebP give much smaller files at the same quality as older JPEGs and PNGs. Lazy loading — only loading images as the visitor scrolls to them — also speeds up the initial view.

Helping images rank

For Google Images, the surrounding content matters: a relevant filename and alt text on a page that is genuinely about the subject. Captions and nearby text reinforce what the image is about.

Use your own, high-quality images where you can. They are more distinctive than stock, build trust with visitors, and for a local business a real photo of your work or premises is far more compelling than a generic shot.