Image Alt

Machines can't read the text inside a picture. A screen reader meeting an image either announces that an image is present and moves on, or reads the filename aloud. Search engines are in the same position: nothing in the picture itself tells them what it says.

So the same page ends up blank for two different audiences at once. A pricing comparison table uploaded as a single image is the standard case. To anyone looking at it the information is dense; to anyone listening there is nothing there, and to a search engine the page isn't about pricing at all.

That's why an attribute created for accessibility became a search item too. Both audiences need the same one line.

Write the role the image plays in that spot rather than a description of the picture. It splits three ways by type of image.

1. Images carrying information. For a chart, write the conclusion the chart states rather than what kind of chart it is. "Signup conversion rose from 12 percent in March to 19 percent in June" beats "line chart."
2. Images with text baked into them. Transcribe the text.
3. Decorative images. Set the value to an empty string. Empty makes the screen reader skip it; omitting the attribute entirely makes it read the filename instead.

Keep it to one sentence, under about 100 characters. An image that needs more explanation than that should have the explanation in the body text, with only a summary here.

There are values not to use: the word "image," the filename, and a list of keywords. Forcing target terms in helps nobody reading and reads as a penalty signal on the search side. For an image wrapped in a link, describe where the link goes rather than the picture.

If the body text right next to it already says the same thing, leaving the value empty is better. Describing images in words as a general practice belongs to alt text.

"The comparison table is image-only, so neither search nor a screen reader gets anything."

The information lives only inside the picture.

"Don't drop alt on decorative images — set it empty. Otherwise the filename gets read."

Omitting the attribute and emptying it are different things.

"Instead of four keywords here, write the one-line conclusion of the chart."

Strip the keyword list and state the actual content.

Pagedeck's blog went through this once. Ravi swept ninety posts and found more than half of the image values either empty or still holding a filename. Splitting the work with Noa, they separated decorative from informative first. A third were decorative, which ended with empty values. Image search traffic rose slightly that quarter. It isn't an item that moves rankings the way the title tag does.