No. There is no notification, and no viewer log. The Meta Ad Library, Google's Ads Transparency Center and TikTok's Creative Center are published transparency tools. None of them tell an advertiser who has looked at their ads.
This is the single most common worry people have before they start competitor research, so it is worth being precise about what an advertiser can and cannot see.
What an advertiser actually sees
An advertiser sees aggregate delivery data for their own campaigns: impressions, reach, clicks, spend, and the demographic breakdown of the accounts their ads reached. All of that describes people who were served the ad in a feed.
Viewing an ad inside a public ad library is a completely separate action. You are looking at a transparency database, not being served the ad. It does not enter their campaign reporting, because it was never a delivery event.
The one place you can leave a trace
If you click through to a competitor's landing page, you become an ordinary website visitor. Their analytics will record a session, and if they run retargeting you may start seeing their ads yourself. That is not identification. You appear as anonymous traffic like any other visitor, and it does not tell them a competitor is researching them.
If you would rather avoid even that, open landing pages in a private window. It changes nothing about what you can learn.
Why the libraries exist at all
Meta launched its Ad Library after the 2016 election cycle, under pressure for political-advertising transparency. Commercial ads came along with it. That history explains both the anonymity and the odd gaps in what gets published, including the fact that spend is published only for political advertisers.
The practical takeaway: competitor ad research carries no disclosure risk. The constraint worth planning around is not being seen, it is that non-political ads vanish from the library the moment they stop running.