Google’s John Mueller said on Twitter that cookie banners are fine as long as you do not replace the content of yourw eb pages with an insterstitial:
Cookie banners are fine. The thing to avoid is replacing your page's content with an interstitial – then we just won't be able to index the content at all.
— ? John ? (@JohnMu) January 16, 2020
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Check your website with the website audit tool in SEOprofiler. If your cookie banner prevents search engines from indexing your web pages, the website audit tool will inform you: