The step is in light of the much-publicised theft of jewellery from the museum, revealed in August.
Mark Jones, interim director of the British Museum, said: “Following the discovery that objects have been stolen from the collection, we have taken steps to improve security and are now confident that a theft of this kind can never happen again.
“But we cannot and must not assume that the security of the collection, in a wider sense, can be achieved simply by locking everything away. It is my belief that the single most important response to the thefts is to increase access, because the better a collection is known – and the more it is used – the sooner any absences are noticed.
“So that’s why, rather than locking the collection away, we want to make it the most enjoyed, used and seen in the world.”
The museum estimates the project to ensure everything is documented and available online will take five years, and once complete, for first time the entire collection will be accessible to anyone who wants to explore it.
Alongside this online resource the museum has announced plans for enhanced access to the museum’s study rooms, where members of the public and academics can see additional items from the collection by appointment.
There is an ongoing investigation by the Metropolitan Police as well as an independent investigation into the thefts of 2000 jewellery items.
Last month the museum said that 60 items have been returned and a further 300 have been identified and are due to be returned.