Have you recently got a parking ticket? This chatbot might be able to help overturn it.

The free service, called DoNotPay, has successfully challenged 160,000 parking tickets—around $4 million worth—in London and New York. It was launched just 21 months ago by London-born Stanford University student Joshua Browder, who says it took him three months to program and who describes DoNotPay as “the world’s first robot lawyer.”

“As far as I know, it’s the first of it’s kind,” Browder told Quartz. “I like to think I created the chatbot before it became cool.”

The service helps users by first asking them a few questions about their parking ticket to figure out if an appeal is possible. The chatbot then helps the user navigate the appeals process.

Of the 250,000 cases it has taken, the chatbot has successfully overturned 160,000 parking tickets—a success rate of 64%. Nine thousand of these cases were from New York, where the bot launched in March 2016. Browder has been described as the “Robin Hood of the internet.”

With the help of some pro-bono traffic lawyers, Browder compiled a list of the most common reasons for parking tickets to get dismissed. Using those details, the chatbot asks users questions like “was a parking sign easily visible?” to determine whether they can file an appeal. If yes, then the bot leads the user through the process of filing the appeal for no fee—and Browder intends to keep it free.

“Parking tickets are a sort of tax on the vulnerable,” says Browder, who gives the example of older people in the UK using scratch-off permits improperly, and getting fined as a result. “It’s so wrong that the government is taxing the group they should be protecting.”

The next stop for DoNotPay is Seattle, where Browder hopes to launch it in early September. Between now and then, Browder is working on a chatbot of sorts for refugees entering the UK, especially addressing potential changes to the system following the Brexit vote. Browder says he hopes it will help refugees get information about their eligibility to seek asylum, but unlike the parking tickets program it will not get involved in the legal process because of the higher stakes involved in getting an application wrong.

Another program on DoNotPay’s landing page allows people to document the fact that they’ve reported their HIV-positive status to potential sexual partners, using text messaging. “I have lots of friends who are HIV-positive, and they’re find navigating around complex disclosure process difficult,” said Browder. Often, people are not aware of the proper way to comply with HIV disclosure laws. By helping people prove that they did the proper disclosure, Browder says he is “preventing innocent people with HIV ending up in prison.”

Browder created DoNotPay after receiving several parking tickets in London. Ironically, Browder’s been so busy working on DoNotPay that he’s somehow ended up with… a parking ticket. Perhaps he’ll use his own service to challenge it.