Images Google can read

Image search is a way in of its own. If someone searches for "larch deck" and your picture is called "IMG_4821", you are not there.

The alt text is one of the few places where you can say what the picture shows in your own words: the service, the place, the job. Google reads it as part of the page.

Visually impaired visitors hear the picture read out as its alt text. Without it the picture is skipped, and a gallery is empty.

• Go through the images on your most important pages. In most tools there is a field called alt text or alternative text when you click the image.
• Write what the picture shows, short and concrete: "New tiled roof on a house in Gävle", not "image1".
• Name the image files something sensible before you upload them.

I give every image a description, the right size and the right format before the site goes live. See what it costs.

The most honest example I have is my own site. The checker gives albit.se 95 out of 100 and still warns about image descriptions. Three images have no description of their own: the customer sites layered at the top of the front page. To the eye they are a single picture, so they carry one shared description on the group instead of one each. The checker counts images one by one and sees three empty ones. I have let the warning stand, because describing the same thing three times would have made the page worse for anyone listening to it.

The common case looks different. The images were uploaded straight from a phone and are named whatever the camera called them. The alt text field was empty when the image went in, and nobody has been back.

The checker counts the share of images with no description. Up to a quarter gives a warning, more than that turns red. The check carries 10 of 100 points. What the text says is not judged, so the word image in the field counts as filled in.

It is also the one place where you can say in words what a photo shows. A job you are proud of stays invisible in image search as long as it is only a file name out of a camera.

Do purely decorative images need a description too?

An image that is only decoration can be left with an empty description field, but then it should also be marked as decorative in the code. If it is merely empty, the checker counts it as missing.

How long should an image description be?

A short sentence is enough. Write what can be seen, with the service and the town if the image shows a job, and skip openings such as picture of.

Does the caption under the image count?

No. The caption shown on the page is its own thing. The description sits in the image's code and is read by search engines and by screen readers.