Photos are a popular method of sharing information on Tumblr. Whether it's to share a stylized graphic you've created or if you want to use a GIF as a reaction to a reblogged post, there are certain methods and rules for how images can be displayed in a post.
Methods for Posting Photos
You can add GIF photoss to your post three different ways on Tumblr. The first is to use a photo post, which displays one or more photos at the top of the post. You can also upload photos to your Tumblr posts by clicking the "Upload Photo" button in the upper right corner above the formatting toolbar. Photos can also be included via URL by clicking the photo icon on the formatting toolbar.
Large photos will be scaled automatically to a maximum dimension of 500 pixels by 700 pixels. Additionally, images will be scaled down on your dashboard, with users able to click the thumbnail to see a larger version. Files larger than 500x700 will be linked to a high resolution version of the image that users can access by clicking the photo.
Animated GIFs cannot exceed 512KB, or 500 pixels wide. Because images are resized when you upload them to Tumblr, larger animated GIF files will strain the server. Files that exceed this limit will likely lose their animation, instead just displaying the first frame of your GIF as the image.
You can include a GIF from externally hosted websites, including Photobucket and Flickr, into the body of your post. This helps bypass limitations imposed by Tumblr, especially for GIF files that exceed the file size limit. However, externally-hosted GIF files will not be displayed on your dashboard and will be replaced by a gray placeholder square. Users can click this square to view your GIF. The GIF will be displayed properly on your personal page.