While Twitter lets you upload photos directly to the Twitter app or website, sharing a video on Twitter requires you to upload the movie file to a third-party app or website.
Share a Short Video
Vine is a mobile application developed by Twitter that lets you upload six-second-long videos and share them in a tweet. Unlike regular videos, which require users to click a Play icon, Vine movies automatically play when a user visits your Twitter timeline.
Tap the Camera icon in Vine's menu bar.
Touch and hold the center of the screen for six seconds to record the video with your device's camera. Alternatively, tap the upward-pointing arrow icon to load a preexisting video.
Tap the check mark icon to save your video. Vine then loads the Share screen.
Post your video to Twitter by enabling the Twitter option on the Share screen and touching the check mark icon.
Share a Video Longer Than Six Seconds
Upload your video to a video sharing site such as YouTube, Vimeo or Dailymotion or, if you want to share a video that already exists on one of these platforms -- such as a music video, a movie trailer or a funny video -- visit the video's page.
Copy the video's URL to your clipboard by clicking it and pressing Ctrl+C. On a mobile device, long-touch the URL and select Copy.
Compose your tweet and paste the URL of the video you want to share in the box by pressing Ctrl+V on desktop or by long-touching and selecting Paste on mobile. Select Tweet to post your tweet.