Keepsakes from Australian soldiers in World War I are on display at the National Library of Australia (NLA) to mark the 100th anniversary of the Great War.

The exhibition, called Keepsakes: Australians and the Great War, showcases the NLA's vast collection of records, artwork and photos from WWI.

Exhibition curator Guy Hansen said families often kept photos and letters as keepsakes to cope while their loved ones were away at war, often for years at a time.

"There's some very moving material," he said.

"In one of the letters we have a soldier writing home a letter to his son to be opened in the event of his death when his son turns 12.

"But there's also letters from soldiers talking about adventures and interesting times."

Mr Hansen said the exhibition sheds light on how Australians experienced WWI.

"Today, there is no-one left who was there. No-one who can tell us what happened, what they saw or how they felt," he said.

"To understand as best we can, we must turn to their archives, which is exactly what we have done in this exhibition."

The free exhibition is on at the NLA until July 19, 2015.