Facebook has indexed almost two trillion posts put on the site by its members to make it easier to find them.
The change means that many older posts will now be added to results when people search for news or information.
The move is being seen as part of Facebook's attempts to keep people on the site rather than go elsewhere to keep up to date with events.
It said options were available for people that did not want their older posts to be more widely accessible.
Tom Stocky, Facebook's head of search, said in a blog post that many people already turned to Facebook when trying to find out how friends and family were reacting to world events. About 1.5 billion searches are carried out on Facebook every day, he said.
The changes that Facebook has introduced will mean members of the social network will now also see posts by strangers alongside those from news organisations and people closest to them.
"Search results are organised to help you cut through the noise and quickly understand what the world is saying about a topic in the moment," said Mr Stocky.
The post also detailed what Facebook users can do to limit who sees the older posts they shared.
Currently the expanded search results are only available to Facebook members in the US.
The move puts Facebook into direct competition with Twitter which recently introduced a similar system called Moments, said Caitlin McGarry on PC World.
"Facebook has a much wider audience than Twitter," said Ms McGarry. "so Facebook's potential reach for its search tools is exponentially larger."