Viddy – regarded by many as the Instagram of online video – has reached 26m and is reportedly adding 1m new users each day.
New talks around financing value the young start-up at more than US$200m.
This compares starkly with social photo-sharing app Color, which despite raising US$41m in funding, has only reached 1m users.
Viddy rival SocialCam now has 36m users.
Last month, Facebook acquired Instagram for an estimated US$1bn.
Viddy is strikingly similar in structure to Instagram and lets users capture videos in quick 15-second bursts and share them with not only the Viddy community but their Facebook and Twitter followers, too.