The Facebook activity of users aged between 13 and 17 would have limited visibility in the network’s new “social graph” search facility, the firm said.
Posts which could identify the teens’ age or location should only appear in searches by friends and “friends of friends” in the same age group.
If an adult were to search for “single females aged 17″, for example, no results would appear, it explained.
Facebook said it was strict about its rules regarding age.
If it had cause for concern about the age of any user – whether it thought they might be older or younger than claimed – it said it would suspend the suspect account and only reactivate it after seeing official government identification.
It added that anyone aged under-17 could not share any of their posts publicly, and all location services were switched off by default, although they could be activated if the young person chose.
Facebook launched a test version of its search feature in January and it is currently limited to select users who have set English (US) as their language.
The move has raised privacy concerns. One blog has gained fame for showing how the tool can be used to carry out potentially embarrassing searches, such as “current employees of Tesco who like horses”.
At the search facility’s launch event the social network said it would take steps to protect its youngest users. The new restrictions – announced in a blog post – aim to fulfil this promise.
In a social graph test carried out on the BBC’s behalf, an adult searched for a specific school. The results only brought up accounts which appeared to belong to adults who had once attended, and over-17s who were still pupils.
Mark Little, principal analyst at research firm Ovum, told the BBC at the time that he was “underwhelmed” by the search facility but could see commercial potential in it.
“I think it’s going to help drive connections within the network between individuals and between companies and pages,” he said.
“If you are increasing connections between friends and pages you are effectively increasing the reach of advertisers.”