noopener
noopener is a link attribute, rel="noopener", that stops a page opened in a new tab from controlling the page that opened it.
noopener is a value you add to a link, rel="noopener", so that the page it opens in a new tab can't reach back and control your page. It's a security setting for links with target="_blank", the ones that open in a new tab or window.
It has nothing to do with rankings. Search engines don't treat a noopener link any differently from any other link.
What it protects against
When a link opens a new tab, the new page used to get a handle on the page that opened it. A malicious page could use that handle to swap your tab for a fake login page while the visitor was looking at the new tab. When they came back, they'd see what looked like your site asking them to sign in again.
noopener cuts that handle. Mozilla's page on noopener explains the details. Current browsers now treat links with target="_blank" as noopener by default, but many sites and content management systems still add it to be safe with older ones.
For example, Kestrel Roasters' blog links to a coffee supplier's site in a new tab:
<a href="https://supplier.example" target="_blank" rel="noopener">our green bean supplier</a>If the supplier's site were ever hacked, it couldn't redirect Kestrel's tab behind the reader's back.
Should a marketer care?
Mostly no. If your CMS adds noopener automatically, it's doing its job. You'll often see it next to noreferrer, which is the one with a marketing side effect: it hides where a visit came from, so your analytics can't tell which site sent it.
noopener doesn't affect AI search either. AI platforms' bots read the page and the link, and the attribute changes nothing about how they treat either.