Similarweb not showing competitors' paid ads

Tried SEMRush?

As for the big data, no one can say their data are 100% accurate.
Maybe you can try Adplexity, Idvert, Adspy, etc.
They are good for FB spying. Especially Idvert(dot)com.

Do you have a subscription or are you using the free version.

Hi Covfefe,

Platforms like Facebook allow advertisers to target very specific groups of people. So, if your competitors are using campaign targeting methods outside the location, or demographics that are being used by services like Similarweb there is no way for those ads to be detected.

Similarweb, like other competitive intelligence tools, collect relatively small data samples and extrapolate from that small data set. Due to the scale and scope of the Internet it wouldn't be practical for small companies to acquire the massive data required for accurate Business Intelligence. Only Facebook, and perhaps the NSA, would have the complete dataset required to produce accurate BI reports, and that would be limited to that single platform.

These business tools typically purchase data from local ISPs and are limited to the data from the one or two ISPs that they are buying, and then extrapolate from there. It's always very incomplete, and very inaccurate. For the most part, the data is not meaningful except on the largest websites that have huge traffic.

HTH,

Don Burk

Yes, You are right many times Similarweb not showing paid results. You should try different tools like Semrush, Majestic etc.