The Memorial Hall polling station in the village of Bishop's Itchington, Warwickshire, as voters go to the polls in the general election.

On Dec. 10, just two days before the United Kingdom went to the polls, some 74,000 political advertisements vanished from Facebook’s Ad Library, a website that serves as an archive of political and issue ads run on the platform. For a while, what the company described as a “bug” wiped 40% of all political Facebook ads in the UK from the public record.

Facebook has said it will not fact-check political ads or restrict the ability for campaigns to target people. Instead, it said it will provide transparency with tools like the Ad Library, the Ad Library report, and the Ad Library API, so the public, researchers, and journalists can monitor how elections play out on the platform. But that only works to the degree that those tools operate properly. It was only the news media’s reporting that brought the issue out into the open.

“The fact that they could have an outage like this that went up to the day before an election, and they didn’t really publicly communicate,” Laura Edelson, a computer scientist at NYU whose work involves using the API, told BuzzFeed News, “that’s just not how you treat a security system. That’s what this is — this is a security system for elections.”

A Facebook spokesperson defended the site’s conduct, telling BuzzFeed News, “We are committed to making sure our transparency tools work, especially around elections. As soon as we became aware of a bug in the lead-up to the UK election, our teams worked around the clock to fix it and communicated publicly about our progress until it was fixed.”

In the wake of the failure during the UK elections, Facebook said it had launched a review of how to prevent these issues, as well as how to communicate them more clearly.

But the events of Dec. 10 are not the first time Facebook’s Ad Library has failed since its launch in May 2018. The API, which is supposed to give researchers greater access to data than the library website, went live in March 2019 and ran into trouble within weeks of the European Parliament election in May. Researchers have been documenting a myriad of issues ever since.

The platform also drew the ire of researchers when it failed to deliver the data it promised as part of a partnership with the nonprofit Social Science Research Council and Social Science One, a for-profit initiative run by researchers — a project that was funded by several large US foundations. Facebook said it remains committed to providing data to researchers, but the SSRC and funders have begun withdrawing from the project due to the company’s delays.

In December, the cochairs of Social Science One’s European advisory committee released a public letter expressing frustration with the lack of data and “eternal delays.”

“This is not an acceptable situation for scientific knowledge. It is not an acceptable situation for our societies,” they wrote, highlighting the need for Facebook data in order to investigate the true impact of the platform on society.

The Ad Library API is the most powerful tool available to monitor political ad spending on Facebook. But it too has been a constant source of frustration for researchers. The API delivers data about all social issue, election, and political ads in the system in a way that makes it possible for researchers and journalists to run in-depth analysis on hundreds of thousands of ads at the same time.

Of all the transparency tools made available by the big social media platforms, Facebook’s ads API offers the most comprehensive view of political ads — when it’s working properly.

Edelson said there are “regular delays of up to a full day between when ads start running and when they show up in the archive.”