An online archive providing details of nearly 100,000 slaves owned by British colonists in Barbados during the early 19th Century has been launched.
The website will soon give details of some three millions slaves
Ancestry.co.uk features the first part of the Former Colonial Dependencies' Slave Register Collection and will eventually detail three million slaves.
Simon Harper, a spokesman for the site, said it would "help bridge major historical gaps for many people".
This year is the 200th anniversary of Britain's abolition of the slave trade.
The Abolition of Slave Trade Act, which was passed in 1807, made it illegal to trade slaves from Africa to British colonies. The legislation required British colonies and territories to keep tri-yearly registers.
The British government was able to monitor slave ownership and stamp out illegal slave trading by registering both slaves and their owners.
No slave could be bought, sold, conveyed, imported, exported or inherited without first being registered, although the registers - lodged between 1815 and 1834 - relied on the willingness of plantation owners to cooperate.
The registers were submitted to the Office for the Registry of Colonial Slaves in London and now reside at The National Archives.
The 1834 Barbados Slave Register has the names of 99,349 slaves.
It also carries the names of 5,206 slave owners, which marks an average of 19 slaves to every owner.
Eventually, the entire Former Colonial Dependencies' Slave Register Collection, from 1812 -1834, will be featured on the website.
It means the online collection, which is free to access, will grow to a list of more than three million slaves from various former British colonies.
Simon Ziviani, from ancestry.co.uk, said: "It is a one-off collection. It is the only record in existence of some slaves even having existed at that time.
"More and more dependencies will come online. We estimate that it will take around nine months for the full collection to come online."
The register is the only collection of slave registers kept by 23 colonial dependencies and overseas British territories which used slaves.