The FCC voted unanimously today to require cable, satellite and radio stations to upload their political files online. Cable systems with fewer than 1,000 subscribers are exempt from the rule. This is another victory for transparency, following a 2014 rule that required broadcast television stations to upload their records of political ad buys online.

These political files contain valuable information about the ads, such as how much they cost and when they ran. Having the political ad files online is important: In some cases they provide the only public information available on groups that are thinly disguised as nonprofit “social welfare” organizations but are, in fact, major campaign players.

Until now, these providers only had to make files physically available to view — if you wanted to know who bought an ad on a radio, satellite or cable station, you would have to go to the provider’s headquarters and ask to see the file on paper. This was also the case for broadcast TV stations until 2014, something Sunlight and our allies fought to achieve.

Our tool Political Ad Sleuth allows anyone to search and sort these political files for valuable information — like who is buying ads, which firms are doing it for them, and how much they’re spending on it — and we’re aiming to integrate these new filings into the tool once they become available. Experts predict to see around $1.5 billion spent on cable TV ads in 2016, so the new requirements will shine some light on a huge, previously dark area of political spending. We expect to see some interesting things in these filings, too: As The Hill noted, radio has “historically been a place for more of the unsavory political campaign tactics,” so this new rule will allow us more insight into who is buying some of the nastier ads of the campaign.

There’s still a lot of work to be done on transparency for political ads, though. Online ads are still very difficult to track, particularly those run by dark money groups, and the FCC still doesn’t require political files to be machine readable or even use a standardized format, which would make searching the files a lot easier. But today’s ruling is a significant step towards transparency for political ads, providing vital information about who’s seeking to influence our elections.