"These amendments will permit the rich documentation preserved at headquarters of the ITS (International Tracing Service) in Bad Arolsen to be opened to researchers and historians," the countries' representatives said in a statement after a meeting in Luxembourg.
The world's largest archive of its kind based in the central German town of Bad Arolsen covers the fates of 17.5 million forced laborers and concentration camp inmates and has until now been open only to them and their relatives.
This fact had led US academics to accuse Germany of trying to cover up its past.
But in April, German Justice Minister Brigitte Zypries said Berlin was now prepared to give the go-ahead for broader access to the 47 million often macabre documents.
Germany reluctant
The decision required the approval of all 11 countries that have held control of the files in the postwar period: Germany, Belgium, Britain, France, Israel, Italy, Greece, Luxembourg, Poland, The Netherlands and the United States.
Germany in particular had been reluctant to give researchers access to the archives, which offer a chillingly detailed account of Nazi wartime atrocities, for fear that it would compromise the victims' privacy.
At the meeting, representatives said that provisions would be taken to ensure the dignity of individuals covered in the files.
"Access to the archives and documents preserved by the ITS will take adequate protection of the personal data into account," the statement said. A spokesman for the meeting said further details on these protective measures would be announced at a later date.
The World Jewish Congress (WJC) welcomed the decision to offer greater access to the archives as an powerful step toward stopping Holocaust denial.
"We are pleased that after 60 years, the millions of written proofs for the Nazi mass murder against Jews will be open for researchers," Israel Singer of the WJC said in a statement from New York.
"It is a strike against all those Holocaust deniers. The opening of the archives is necessary to continue research into this dark chapter of our history; it is necessary to preserve the past so future generations could learn a lesson from it."
Holocaust details
Researchers have said the files, which fill 27 kilometres of shelf space, will not lead to a rewriting of history but will help give a clearer, more personal picture of the suffering inflicted during the Holocaust.
The archives hold the names of prisoners along with intimate details of their lives including pseudo-medical experiments endured at concentration camps, diseases and children born out of wedlock. Some are labeled "homosexual" or "schizophrenic".
The entries reflect not only the vicious nature of Adolf Hitler's dictatorship but also its pettiness and perversion.
One record shows that the Nazis counted the head lice of prisoners held in present-day Poland, another that the commander of the Mauthausen concentration camp in Austria had 300 prisoners shot in the head in a matter of hours to celebrate Hitler's birthday.
The ITS, an arm of the International Committee of the Red Cross, has for decades administered the archives and responded to requests from victims and their families.