Alt text is a brief textual description of images added to web pages in order to help search engines understand the image content.
A recognized ranking factor, alt text can help images rank in Google Images for relevant search queries. That can drive additional traffic to related site pages.
Modern content management systems (CMSs) like WordPress and Drupal provide a blank field to enter alt text into.
Then the CMS automatically wraps the text in an alt attribute. This helps search engines find and process the alt text.
<img src="orange-tabby-cat.jpg" alt="orange tabby cat sitting in windowsill">
The alt text also becomes the snippet of text that appears under the image in standard web search results. A concise, keyword-relevant description helps the image achieve better ranking in search engines.
Alternative text also displays when images fail to load and it's used by screenreader devices to help visually impaired users.