He has watched racists translate Klan codes into email addresses and spread Nazi insignia on message boards since the 1980s. “As each new element of the internet emerged, white supremacists were right there with it,” Mr. Pitcavage said.

The echo symbol is emblematic of a new class of bigotry born and bred online. “Anti-Racist Is Code for Anti-White,” a slogan that was lifted from an early-2000s pro-segregationist tract called “The Mantra,” has proliferated online as a piece of white supremacist copypasta — text that’s obsessively copied and pasted across internet forums. The mathematical sign for “not equal” has been repurposed as a statement against racial equality. Like the echo, it leverages the computer keyboard to create the new supremacist symbolism for the modern era.

The Anti-Defamation League has called the alt-right “the new white supremacy,” and its figures poke fun at their grandfathers’ displays of white pride even as they create their own. The hosts of “The Daily Shoah” performatively pronounce “white” as “huh-white,” a mocking imitation of a good ol’ boy. The podcast’s echo winks at the cheesy sound effects favored by old-school right-wing radio shock jocks.

Much of the alt-right’s language and imagery is borrowed from 4chan, an anonymous, ephemeral message board that revels in politically incorrect jokes and nihilistic posturing. The roiling discussion on 4chan “tends to represent a libertarian, white, male perspective,” said Ryan Milner, a communications professor at the College of Charleston who studies online groups. “Its humor plays with outright stereotypes that veer into white supremacy.”

Both the alt-right and 4chan share favorite insults, like “cucks” (feminized men) and “normies” (the unsophisticated masses) and work from the same meme palette, dealing out pop cultural barrel-scrapes that perpetuate racist and anti-Semitic tropes. Pepe the Frog, a favorite cartoon character on 4chan that has since become a mainstream teenage idol on Tumblr, has emerged as an unofficial alt-right mascot. It’s just that on alt-right accounts, Pepe appears with an exaggerated hook nose or comes adorned with a Trumpian toupee.

The alt-right takes the online subculture’s discourse and dials it up to the level of political agitation. The Southern Poverty Law Center has charted fervent support for Donald J. Trump among “right-wing extremists,” who share “exultant memes celebrating Trump’s ascension.” In April, the center reported that some of Mr. Trump’s rhetoric can “drive mainstream attention to racist memes.”