All images displayed on our websites have "alt" tags, which are hidden tags that describe what the images are showing. Alt tags are important to search engines and screen readers for visually impaired viewers.
Image Alt tags are meant for describing an image accurately and concisely. Therefore the Alt tags have a much more specific role compared to the Captions which can be any sort of rambling prose.
For example, this photo's Caption might be something like: The fishing village of Reine is on Moskenesøya Island, perhaps the most rugged and impressive of the Lofoten Islands. This rare calm day provided the opportunity I was hoping for to photograph the reflection of the village and the massive peak behind it. Every person around here this morning was just in awe of the scene.
But the Alt tag should be something more concise and directly descriptive, like: A reflection of a jagged mountain peak above the fishing village of Reine on Moskenesøya Island in the Lofoten Islands of Norway.
See how the second version is more concise and directly descriptive? With the Alt tags we only want to directly describe the image that people are looking at -- without any superfluous info. Here are some guidelines for correctly entering image Alt tags:
- Keep it short, concise, and directly descriptive of the image itself.
- It should be a short, readable sentence.
- You should certainly try to include image-relevant keywords, but do not go overboard with keyword-stuffing, which will do more harm than good.
- Do not include "Photo of..", "Picture of...", etc. in the alt text. The alt text is already within the code context of the image, so this is already known and assumed.
Entering custom Alt tags for all your photos is optional. If left blank, the Alt tag will default to the photo caption, title, or keywords, in that order. So if your caption is already directly descriptive of the image, just go ahead and leave the Alt text blank - that's totally fine.