Sometimes your gif will upload and be a still instead of an animation. This is because
1. your gif is bigger than 500K
or
2. the width of your gif is wider than 500 pixels.
Sometimes you’ll have trouble uploading a gif. You’ll wait for like five minutes for your gif/picture to upload only to get the stupid “error uploading photo” message over and over again. I’ve spent hours and hours trying to figure out a way to solve this and there are actually several solutions:
1. upload it onto photobucket or tinypic or deviantart (don’t use flickr. it doesn’t hold gifs very well). then use the url they give you (for the actual image. NOT the url with all the shinanigans on the side and stuff) and upload it on a new photo post with that url.
1a. if you still get “error uploading photo”, open a new text post and copy the HTML embed code thing from photobucket or tinypic or deviantart. then open the HTML source editor (the last button in the row of buttons on top of the post box) and paste the code into source editor. your gif should be able to upload into the text post.
1b. THEN, if you want the whole image to display instead of a minimized one that people would have to click on to get the whole image on their dashboards, you can right click and “view image” your image from the text post. copy the url. paste it in a photo post. upload.
2. get the tumblr bookmarklet from the goodies section [here]. click “view image” for the uploaded version on photobucked/tinypic/deviantart. click the bookmarklet (“Share on Tumblr”) and upload it that way.
3. your gif will only work if it is a frame animation. go check to see that it is. if not, make it a frame animation.
4. if your gif meets the 500k & <500pixels width and the previous solutions didn’t work, it’s probably because your gif is way too vibrantly colored (i know. it’s weird how tumblr works). go to photoshop and turn down the saturation for the gif. after you do this, i guarantee that your gif/photo will upload in a photo post.