Use Holocaust records
If you've established that you have Jewish ancestors but want to learn more about them, people recommend using the Holocaust database. This will, of course, be especially useful for those who know they have family members who lived in Europe during World War II. However, it can still be useful for those who lack specific knowledge.
Assume you know the names of some older relatives but not their histories. You can learn more about them and your family history by searching the Holocaust database—but keep in mind that learning about relatives' Holocaust stories can be emotionally draining.
It should be noted that only about 60% of the Holocaust database is accessible online. The rest can be seen in person at the United States Holocaust Museum.