Jews in this category feel pride in being Jewish and a strong sense of belonging to the greater Jewish community. But they say their connection is based mostly on culture and ancestry, not necessarily on belief in God or observance of religious law. A large majority said remembering the Holocaust, being ethical and advocating for social justice formed the core of their Jewish identity.

The report, released Tuesday by the Pew Research Center's Religion & Public Life Project, is an in-depth look at how American Jewish identity has changed in recent decades. The findings track closely with a 2012 Pew report that found about 20 percent of Americans in general said they had no religious affiliation, an increase from 15 percent in the last five years.

Secularism has long been part of American Jewish life, which includes movements such as the Society for Humanistic Judaism founded in Detroit in the 1960s. However, the Pew survey found the percentage of American Jews who say they are atheist, agnostic or have no particular religion is highest among younger generations.