If you ever wondered whether you had a World War I hero in the family you can assuage your curiosity this weekend.
Winston Churchill's record is among those viewable on the site
More than five million medal records will be online from Remembrance Sunday on the National Archives website.
Records of famous people such as King Edward VIII, Sir Winston Churchill and poet Siegfried Sassoon are also there.
TV satirist Ian Hislop, whose family history will be shown on BBC2's Who do you think you are?, called it "a huge leap forward" for such research.
The medal index cards, held at The National Archives, Kew, provide the closest thing there is to a 'roll-call' of all those who served in the Army - including the Royal Flying Corps - in the Great War, as every individual who served abroad in the Army was entitled to one or more campaign medals.
Then there are the more recognisable names.
When Churchill served in France he was commanding a battalion of the Royal Scots Fusiliers, entering France on 18 November 1915.
He was a Major in the Oxfordshire Hussars at the time he claimed his medals and he was awarded the 1914-15 Star and the British and Victory Medals. He is listed as the Right Honourable WLS Churchill.
There is no trace, on the other hand, of T E Lawrence - Lawrence of Arabia.
Lawrence had little wish to be remembered as a war hero, preferring to be known as a man of letters.
"Officers had to apply for their campaign medals but Lawrence had no interest in awards for himself and declined, so he does not have an entry," explained National Archives' military expert William Spencer.
It helps when searching the website to have gathered as much information as possible, such as the rank, unit and service number, as there are often several people with the same name.
King Edward VIII won the clasp and rose indicating he was fired upon
People from all walks of life are represented - officers and soldiers, civilians whose jobs took them into the war, and thousands of people from Commonwealth countries.
If your relative happened to be Abuel Haggag Ahmed Mohamed of the Egyptian Labour Corps, your search would be simplified by the fact that he was the only serviceman out of the 5,434,048 listed with the rank of camel clipper.
"It is sometimes a case of lateral thinking to a certain degree," says Mr Spencer.
"Sometimes there are complications such as not knowing whether someone was Alfred or Fred, or that someone is listed under their first initial and surname, so you need to get as much accurate data as possible to pin it down.
"The information has been available for a long time on microfiche and proved very popular. It was fairly easy to transfer it online and we are sure there will be lots of call for it."
Very few World War I veterans, however, will be looking up their own records as their number now lies in the low double figures.
The Royal Star and Garter Home in Richmond, south west London, lost its last member of the exclusive club several years ago but staff there feel the release of medal information will be of great interest and value.
Marketing and communication manager Kelly St Claire told BBC News: "It's excellent news. It is very important that this history is kept and that it is accessible to the general public.
"Everything that makes access easier is a step forward as so many more people are wanting to trace their history. And the fact there are so few veterans left makes it all the more important."
Searches on the site, which has been partly available since August, are free and downloading digital images of original documents from the site - http://www.documentsonline.nationalarchives.gov.uk/ - costs £3.50.