Flickr has built up a global following as an photo sharing site, but now it is going to challange YouTube's dominance by also showing videos.

Flickr, which is owned by Yahoo, has formally announced its plan to start to offer video streaming.

Movies will be limited to 90 seconds in length and 150MB in size, and they will be shown as thumbnails alongside users' photos.

And Flickr visitors will be access all of the tools for videos that they can currently for photos - namely users can add comments, captions, comments, geotags, and privacy restrictions so only friends or family may view their videos.

Videos are shown on pages similar to photo pages, and can be embedded on other sites.

The Flickr team says that the decision reflects the fact that more and more digital compact cameras and DSLRs offer video recording facilities.

And it is short movies captured by Flickr visitors of their friends and family that are expected to be uploaded.

This is compared to YouTube where everything seems to appear from clips from movies to political ads, and where clips up to 10 minutes in length can be uploaded.

This is the key difference between the two sites, adds Yahoo, who insists it is not going up against YouTube.

"People aren't using YouTube to share their personal short-form video clips", said a Flickr spokesperson.

"Ninety seconds helps us define that rebroadcasting commercial content is not what this site is for", said Neilson said.

The Flickr team adds that only those with "pro" subscriptions will be able to publish videos, but as with photos, those with free Flickr accounts and the public will be able to watch them.

The site will support videos in AVI, MPEG, and MOV formats, showing them with a Flash player but storing the original, too.

The existing Flickr upload tools will work with videos.