Img alt tag showing different value then entered

Adding an alt attribute in the media library does not add or update it on any of your pages where it’s already been inserted in content.

When you add an image to content using the editor, it’s added as an HTML <img> tag, including alt attribute. Once it’s been added, it’s just HTML, so making changes in the media library can’t affect it.

To add alt text to your images you’ll need to go into each page, select and edit the images there, and add the alt text that you want.