Back in May, at the height of Facebook’s Cambridge Analytica privacy scandal, the company made a timely announcement: Facebook users would soon be able to clear the browsing history connected to their Facebook profile, meaning that the company would no longer link users to the apps and websites they visited off of the social network.

The product, called “Clear History,” got a lot of attention. Not only is browsing data important — Facebook uses it to target people with advertising — but CEO Mark Zuckerberg announced Clear History himself during Facebook’s annual developer conference. Clear History was an olive branch meant to show everyone how serious Facebook is about privacy.

“This is an example of the kind of control we think you should have,” Zuckerberg wrote in a post. “It’s something privacy advocates have been asking for — and we will work with them to make sure we get it right.”

As it turns out, clearing your browser history was harder to implement than Facebook expected. It’s been more than seven months since Zuckerberg’s announcement and Facebook hasn’t mentioned Clear History since.

Facebook’s Chief Privacy Officer Erin Egan said at that time that it would take “a few months” to build. Now Facebook tells Recode it won’t be ready for several more months.

Product delays aren’t uncommon in the tech world, but Clear History was announced to show users how serious Facebook was taking their privacy. Now it may be a whole year between that announcement and product testing.

“It’s taking longer than we initially had thought,” admitted David Baser, the head of Facebook’s newly created privacy product team, in a recent interview with Recode. “We did underestimate how long [this] would take.” Baser said Facebook will “deliver the product for testing by spring of 2019.”

Baser chalked up the delay to two technical challenges, both of which are related to how Facebook stores user data on its servers.

1. Facebook data is not always stored in the same way it is collected. When Facebook collects web browsing data, for example, that data set includes multiple parts, like your personal identifying information, the website you visited and the timestamp for when the data was collected.

Sometimes those pieces of data are separated and stored in different parts of Facebook’s system. Finding them all so that they can be cleared, especially once they’ve been separated, has been a challenge, Baser said.

2. Facebook currently stores browsing data by date and time, not by which user it belongs to. That means there was no easy way within Facebook’s system to see all the browsing data linked to an individual user. Facebook had to build a new system that stored browsing data categorized at the user level. “That was not very simple, actually, in practice for us to build,” Baser said. It’s an important element, though, because in order for users to go in and clear that data, they need to be able to find it.

Facebook collects vast amounts of user data and has been criticized for years for not being clear enough about what it collects and why. That criticism came to a head in 2018, when users and regulators started to seriously question the company’s data practices, and CEO Mark Zuckerberg was summoned to Washington to explain it all before Congress.

Facebook claimed repeatedly that data and user privacy is a top priority. It’s why Baser’s team even exists. The group, which focuses exclusively on privacy products, was just created in May during a company-wide restructuring.

But things haven’t gone well for Facebook since then. The company announced a massive security hack in September, plus a number of software bugs with privacy implications, including one on Friday that may have exposed users’ private photos to app developers. It took Facebook more than three weeks to announce the breach publicly after alerting authorities. Not coincidentally, Baser says one of the focuses for his team is coming up with a faster and clearer way of alerting users of privacy mishaps.

Explaining Clear History to users will likely be its own challenge. There’s a reason that Clear History isn’t called “Delete History”: Using the feature will disassociate browsing data that Facebook collects from your specific account but it won’t be erased from Facebook’s servers completely, Baser said. Instead it’s just “de-identified,” which means it’s stored by Facebook but no longer tied to the user who created it.

Why can’t Facebook just stop collecting your browsing history entirely? Well, it could, but a large part of Facebook’s business depends on collecting this kind of browsing data, so it would cripple a big revenue stream. Facebook is an ad company, and that means it needs to know which sites users visit so it can properly charge advertisers, Baser said. Facebook might charge an advertiser each time it drives a visit to that advertiser’s website, for example.

“We can’t actually stop data collection,” Baser said. “But what we can do is strip away the identifier that would let us know whose it was.”

Which is all to say that Clear History should mean that you won’t see those sometimes creepy ads on Facebook about products you’ve looked at on other websites. It won’t mean, however, that Facebook has stopped watching you while you browse the web.

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