I was going to make a comment about those just tuning in, but Tumblr just put my cursor at the far left of my screen like that was a normal place to enter text, and then tried to make the entire textbox a link to the gif source. Staff better fix this.
With the new update, Tumblr forced gifs (and possibly other images?) to stretch to fit the width of the post. With the new option in Tweaks 3.3.1, we’ve added a checkbox to the gear drop-down in post creation to turn that off.
As it stands now, the option only works on images already added to the post, so make sure you use it after you’ve added all the images you want original-sized.
For gifs added from the gif browser, the “originally posted by” is still full width:
