How to optimise images for SEO?

Image SEO is often overlooked because text seems to be the most important. But images affect site speed, usability and how Google understands the context of a page.

If the photo is called IMG_4829.jpg, it tells neither the person nor the search. If the file is too large, the website loads more slowly. If the alt text is empty, another opportunity to explain the meaning of the image is lost. Small things, but they add up.

The file name must be clear

Image optimisation starts even before the file is uploaded. The file must be clear, not too heavy and relevant to the theme of the page. It is better to use a clear name, such as sites-structure-plan.png, rather than a random set of numbers.

That doesn't mean you have to cram it full of keywords. The title simply needs to describe the image. Naturally, briefly, without overdoing it.

The speed of the website also depends on the size of the images. When a page loads slowly, one of the most common reasons is that the pictures are too big, especially on your phone. Mobile speed is important both for the user and for SEO.

Alt text is no place for a list of keywords

The alt text should explain what is seen in the picture. The description of the image helps accessibility while providing context for search engines. Bad alt text would be one word for SEO. Better would be a clear sentence about the image that is on the page.

SEO optimisation works better when all the elements on a page speak to the same theme. Search engine optimisation is not just about text, so the title and description of an image must also be thought through. If the article is about the structure of the website, the description of the image should also be about the structure, not about something random.

What to check before uploading images

• the file name is clear and concise
• the image is not too large
• whether the alt text naturally explains the image
• whether the image actually contributes to the text and does not just take up space

If you want a broader view of SEO, this topic is worth combining with the article on website visibility on the internet. The pictures are only one part, but a good part.

How big should the picture be

A common mistake is to pose photos taken directly from your phone or camera. They can be several megabytes in size, even though they appear in a small block on the page. In this case, the visitor downloads more data than necessary and the website loads more slowly.

In practice, a simple rule is worth having. If an image is used inside an article, it often doesn't need a huge format. If it's the main hero image, it can be larger but still optimised. It is not only the dimensions that matter, but also the weight of the file. Sometimes an 1800 pixel wide image, well compressed, will work much better than a smaller but poorly exported file.

• don't upload original multi-megabyte photos without optimisation
• Keep the quality for key images but reduce the file weight
• only use the size you actually need for illustrations in articles
• please write the file name according to the subject of the image, not a random number

What good alt text looks like

Alt text must be simple. If the image shows a mock-up of a restaurant menu design, write it that way. There is no need to put five keywords in a row. A good description helps someone who can't see the image to understand it, while giving Google a clearer context.

A good example would be „SEO, images, optimisation, website“. This text explains nothing. A better option would be „restaurant menu design layout on a dark table“. If the article is about the structure of the website, the alt text can describe a diagram or a page plan. It is important that it is about the image, not about the desire to appear in a search.

• write what is visible in the picture
• Avoid keyword lists
• don't leave alt text blank for important images
• decorative images don't need a fake description

If you want to continue the SEO theme, it's worth reading SEO basics for your website, where to start. This theme is naturally complemented by How can I increase my website's online visibility?.

If you have a lot of old, heavy or unclearly titled images on the website, please get in touch. We can review the images and tidy it up so that the pages load faster and are clearer for searching.