Instagram recently announced the ability to add alternative text to photos. This allows creators to provide a visual description for people who may be using assistive technologies such as screen readers.
For New Photos
When entering your post’s caption, you can scroll down and tap Advanced Settings. From the Advanced Settings page, Tap Write Alt Text, and enter your Alt Text in the field.
For Existing Photos
To add Alt Text to previously uploaded photos, go to the photo and access the Edit page. You will then see an “Add Alt Text” link appear at the photo’s bottom right corner. Tap this link, and enter your Alt Text in the field provided.