Ancestry, the genealogy and DNA testing company, has digitized millions of records of people who were displaced or persecuted in the Holocaust and made them searchable online at no cost.

The announcement this week drove numerous genealogists to the site to try to fill in longstanding gaps in family stories. It also spurred a debate about whether enticing people to sign up for a for-profit database with such sensitive public records was appropriate. 

Rachel Silverman, a private genealogist specializing in Jewish family history, said she was enthusiastic about the development, but added that it was too early to know how useful the records would be. 

“Every American Jew has people they lost,” she said. “It’s just the matter of the degree of separation.”

The release includes passenger lists of millions of displaced people, including Holocaust survivors and former concentration camp inmates, who left ports and airports in Germany and other parts of Europe from 1946 to 1971. It also includes records of millions of people with non-German citizenship who were incarcerated in camps or otherwise living in Germany and German-occupied territories from 1939 to 1947. 

The records will not tell people who they lost in the Holocaust if they don’t already have an inkling. Instead, the records could provide additional hints at why a relative took one escape route instead of another, Ms. Silverman said. 

“In genealogy, the almighty why is the hardest,” she said. “Why did my family end up in Atlanta when they were from the small town in Germany? When we find out how travel was arranged, that might open new doors.”

Allan Linderman of Newbury Park, Calif., for example, had researched his 87-year-old cousin’s journey to the United States before the documents’ release. Born in Poland in 1932, the cousin, Irving Rock, and his family fled their home in the early 1930s. They then spent more than a decade scrambling for safety, moving from one place to the next. Because he is still alive, Mr. Rock offered some details from memory. But in the trauma and chaos of relocation, he could not recall when precisely he left Germany forthe United States.