The archive also doesn’t show which categories of users the ad was aimed at, such as people with a certain political affiliation. The Internet Research Agency, a Russian outfit linked to the Kremlin, used Facebook’s platform to target its divisive messages to audiences interested in topics like patriotism, illegal immigration and Bernie Sanders. The archive also doesn’t show you how many times Facebook users interacted with an ad, by sharing, liking or commenting on it.

Rob Leathern, Facebook’s director of project management, said it was more important for Facebook to provide demographic details about the audiences that saw political ads than to show ad-targeting information. Facebook has recently eliminated many audience targeting categories , like “Young, black and professional” and “Indigenous people of the Americas, ” and said this month that it planned to eliminate more. Facebook said it planned to issue a report with aggregate facts and figures such as which advertisers spent the most on political ads.

The Google archive does not show political ads for candidates in state elections or ads on political issues.

The search giant lets advertisers, including political campaigns, target ads based on consumers’ keyword searches on Google. But the archive does not disclose the keywords that campaigns may have used to target a particular political ad. You also can’t see a demographic breakdown by gender and age of the audience who actually saw the ad.

Google said it was considering extending the archive to include ads for candidates running for state offices. In a report in August, the company listed the six top search terms that campaigns used to target political ads during the previous week. These included “ACLU,” the civil liberties group, and “Rick Scott,” the governor of Florida who is running for Senate.

The Twitter archive currently has the biggest limitations. For state or local political ads on Twitter, you can see only current ads — and those don’t include demographic audience data or spending data.

If you don’t know, or can’t locate, the Twitter handle of the campaign you are looking for, you won’t be able to search for its ads. In addition, the company doesn’t show certain ad-targeting categories — like sports interests — that a campaign may use have used to target an ad.