Image SEO: alt, weight, and sizes
Images are both traffic from image search and a significant part of the page weight. Checking image SEO reveals issues: missing descriptions, heavy files, incorrect sizes.
What is checked
- Alt attribute — a textual description for those who cannot see the image and for search engines.
- File weight — the main source of slow loading on most websites.
- Sizes — whether a huge image is scaled down to a small block by the browser.
- Format — modern formats weigh significantly less at the same quality.
- Specified width and height — without them, the layout jumps during loading.
What to do with interface screenshots
Screenshots last longer than the interface they depict: in six months, buttons may have moved, but the image remains. Therefore, it is useful to keep the originals and take screenshots consistently, so updates can be mechanical. In our knowledge base, screenshots are taken according to recipes and are retaken by the same team — otherwise, maintaining a hundred articles would be impossible.
How to write alt
| Poor | Good |
|---|---|
| Empty | Description of what is in the image |
| "img_2024.jpg" | "Report on the cascade: publications by levels" |
| Keyword stuffing | Natural phrase where the query fits |
| Identical alt for all images | Unique for each |
For decorative elements — backgrounds, dividers — alt should be left empty: this way, screen reading programs skip them.
Traffic from image search
This is a separate source, and it is noticeable where the image is the answer: recipes, interiors, diagrams, products. To utilize it, three things are needed: a meaningful file name, an alt description, and a caption next to the image. Plus, the image itself must be accessible for crawling — a folder with images closed in robots.txt is more common than it seems.
Order of work
- Find the heaviest images and compress them — browser compression will help.
- Set width and height to eliminate layout shifts — see Core Web Vitals.
- Write meaningful alts on the pages you are promoting.
- Check the result with speed measurement.