What just happened? A website that helped San Francisco residents avoid parking tickets has been effectively killed off by the city, just hours after it went live and was in the process of going viral. Find My Parking Cops stopped working after the San Francisco Municipal Transportation Agency (SFMTA) changed the government site where the tool was scraping its data, blocking its access to the information.

Find My Parking Cops, which imitates Apple's Find My Friends app in both name and design, let users see the locations of parking enforcement officials on a map in near real-time.

The website identified each officer on duty by their initials and showed where they were – based on the last citation they made. There's even a leaderboard showing which officers racked up the most money in fines: the top enforcer was on more than $20,000 before the app was affected.

The system worked by grabbing information from the SFMTA website, which anyone can use to search for a citation number and see a copy, including details about the vehicle that was cited, where the incident occurred, and the reason.

Creator Riley Walz says he got the idea for the site after one of his roommates received a parking ticket. "I actually don't have a car," he said. "But my friends do and I know that parking tickets are kind of notorious in this city."

Walz noticed the nine-digit identification number on the ticket and started searching for patterns. The software engineer said he figured out that ticket citation numbers are predictable, "which means I can effectively scrape them."

Walz went into more detail about the pattern on his blog: "add 11, except add 4 if the last digit is 6. So no ticket can end in 7, 8, or 9. So the ticket after 984,946,606 is actually 984,946,610, and after that is 984,946,621." He suspects that this bizarre pattern is the result of software limitations used by parking control officers.

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The website's leaderboard made for interesting reading. The top five officers had all handed out tickets totaling more than $15,000, while the top Officer 0336 had generated $20,150 for the city from 192 tickets – and this is all in one day. But considering officials handed out more than a million tickets amounting to over $100 million last year, the figures aren't too surprising.

Sadly for San Francisco residents, the SFMTA changed its website hours after Find My Parking Cops went live, removing parking citations from public view.

"In rare lightning speed, the SF government changed their site within hours of this site going live. I can't get data from it anymore," the app now reads.

"We made sure that all access to citation data was via authorized routes," an SFMTA spokesperson said in a statement. "When our staff's safety, and personal information of people who have received parking citations, is at risk, we must act on that swiftly."

In the few hours it was working, the site attracted over 50,000 views, indicating just how popular it would have been.

Masthead: Wayan Vota