(Pocket-lint) - Twitter has been testing disappearing tweets - called Fleets - for a while. And, after testing it in several countries it has now decided to roll it out globally. It'll be coming to iOS and Android in the coming days. 

Fleets are, essentially, Stories just like those in Instagram and Facebook. They disappear after 24 hours. You can't retweet a fleet and you can't even reply - though you can send a direct message or send an emoji. As with Stories, you can customise how they look and share photos and video as well as text. Stickers will also be available soon. 

Twitter clearly hopes it goes some way to helping people tweet thoughts without the pressure of thinking those tweets will remain around permanently - product manager Sam Haveson suggests the feature will help people "feel more comfortable" with a "lower pressure way for people to talk about what’s happening".

Twitter previously tested the feature in Brazil, Italy, India and South Korea and it says that yes, people did share more as a result "Fleets helped people feel more comfortable sharing personal and casual thoughts, opinions, and feelings." While that may be true, the jury is definitely out on Fleets in terms of what it might mean for Twitter as a platform (it's a fundamental change) as well as Twitter's chronic abuse problem. Twitter recently introduced new ways to control who can reply to your tweets

It seems there will be a Fleets bar in the new apps - we don't have it yet - but it's unclear whether you will be able to turn it off - we certainly hope Twitter will offer this as an option. 

Fleets also take away one of the best features of Twitter; that all posts can be located with a URL - even ancient tweets that form a historical record. Since Fleets just disappear, that isn't quite so compelling. 

Writing by Dan Grabham.