Due to a couple of different reasons, from today we have set a new limit on GIF's to 4MB for posting to Twitter. This update, although more limiting, will significantly reduce the likeliness of posts containing GIFs being rejected by Twitter.
For transparency, in the upcoming weeks, we will be changing our provider for Image + Video uploads. With this change, we are likely going to be able to increase the limit for GIF's again, along with introducing better compression rates for larger videos.
Our new uploader will feature many new features, including the ability to add media directly from Instagram feeds, Google images, Dropbox and other solutions for customers on paid plans.
-The Product Team.