Alt Text Descriptions for Images in Twitterrific (iOS and macOS)
Twitterrific has the ability to include a text description for any image you post to Twitter using the app. These text descriptions are especially useful for those who use the social service via Voice Over, an accessibility setting for the blind and hard of seeing. Images that have descriptions can be read to these users so they have a better understanding of what's being posted.
To include a text description of an image in Twitterrific, tap the camera button to open the image picker. Next, select one or up to four total images to attach to the tweet. Once the images are attached you can then tap (or select with voice over) the image thumbnail at the bottom of the compose window to be presented with options to either delete the image or include a text description.
Note that text descriptions must be fewer than 420 characters total or you will receive an error when attempting to post.
Do your best to describe the image for anyone who would not be able to see it normally and then tap to accept the description. When you press the Tweet button, the image description(s) will be included with your tweet for others to listen to as they browse their Twitter timelines.
Why don't I hear image descriptions read to me on my own posts in Twitterrific?
Many times it usually takes Twitter a few seconds (or even up to a minute) to process an image description and attach it to the tweet in the streaming API.
This slight delay means that the tweet that Twitterrific immediately pulls from the service to display in your own timeline can arrive without the description. Since Twitterrific caches tweets (to increase scrolling performance), your tweet is stored without the description. You see it as not having it attached, but to everyone else the description is there and working.
A work around for this on iOS can be found by clearing your timeline cache. Open the account panel and then tap and hold on your account. When the red X appears on the account, select "Clear timeline cache". This forces the app to delete all the old, cached versions of tweets and re-download them. Once re-downloaded, if you view a tweet of your own that has an image description, Voice Over should read it to you.
Wish hope to improve this flow for users since it makes it appear that text descriptions are broken but there's little we can do about it for now. Until Twitter delivers the text descriptions at the exact same time as the tweet itself, Twitterrific will continue to cache incomplete versions of the tweet and things will seem out of whack.