Action Details
Requirements and how-to articles for Twitter's action:

Sharing videos on Twitter.

You need this to get it done:

Minimum video length: 1 second
Maximum video length: 140 seconds/2 minutes and 20 seconds (you can upload a video which is longer, but will prompted to crop it shorter)
Maximum file size: 512MB
Web file format(s): .mp4/.mov
Mobile app file format(s): .mp4 with h264 compression and .aac audio
Web minimum resolution: 32 x 32 pixels
Web maximum resolution 1920 x 1200 pixels/1200 x 1900 pixels
Web maximum frame rate: 40 fps
Web maximum bitrate: 25 Mbps
Web aspect ratios: 1:2.39 - 2.39:1 range (inclusive)
Text (optional)
Text to accompany the shared video (maximum of 280 characters.)
Requirements missing or found errors? Report

How-To Articles
A list of useful links for you:

How to share and watch videos on Twitter
Twitter's official help section describing various ways to share and consume video.
Link missing here or found errors? Improve How-Tos