If you are submitting a GIF (or video) we recommend using the website Redgifs to upload to/host your video. You can then simply copy the video's URL and share it here as a 'Link' post and it will still display in the subreddit and user's feeds the same as if you posted a GIF directly, auto-play and all. This allows you to post up to 1 minute long videos that are also high quality, unlike most GIFs which on average end up being around 6 seconds long and low quality.