SAN FRANCISCO — Twitter is amplifying hate speech in its “For You” timeline, an unintended side effect of an algorithm that is supposed to show users more of what they want.

According to a Washington Post analysis of Twitter’s recommendation algorithm, accounts that followed “extremists” — hate-promoting accounts identified in a list provided by the Southern Poverty Law Center — were subjected to a mix of other racist and incendiary speech. That included tweets from a self-proclaimed Nazi, for example, a user the account did not follow.