A driver in California was caught on video spewing an ugly, racist rant against Asians when another motorist wasn’t driving fast enough for her — but she won’t face charges, police said.

The unidentified woman launched into the xenophobic tirade after she got stuck behind another driver, James Ahn, in Fremont — and started harassing him over his race despite the fact he was driving the posted speed limit of 35 mph, he said.

“As I changed the lane, she kept driving towards my car gesturing to crush me and cutting in front of me to slam on the break,” Ahn posted Monday on Facebook. “I later realized that this was more like a hate crime than a road rage.”

A passenger in Ahn’s car then started recording the dispute and caught the woman making an offensive gesture using her hands and eyes toward Ahn, who is originally from South Korea, according to his Facebook profile.

“This is not your f–king country,” the woman said. “This is my country.”

The irate woman also commented about Ahn’s appearance, saying, “Oh my God, Chinese ugly, ugly Chinese,” according to the 9-second clip.

Ahn reported the incident to Fremont police on Wednesday, but investigators determined that no crime actually occurred, police spokeswoman Geneva Bosques told The Post.

“What we have here is hate speech,” Bosques said during a telephone interview. “And we met with her and she does not deny that she did any of this. But she claims he started it by saying to go back to her country.”

The female driver, whom Bosques declined to identify, told investigators that Ahn actually started the dispute.

“All that we could establish is that this was derogatory remarks between two parties,” Bosques said. “There was no threat and there was no crime committed. We did document everything in a report and we classified it as a disturbance.”

Bosques said investigators were unable to justify charges of reckless driving against either motorist.

“You could call this hate speech but as horrible as it is — and we clearly don’t condone any of it — it is protected by the First Amendment,” she said. “The other piece of this is that these two motorists were driving in traffic yelling at each other and the situation could’ve been worse for other drivers around them.”

Ahn did not return a message seeking comment. The video posted to his Facebook profile had been shared more than 3,800 times as of Thursday.