Noindex Is a Scalpel. Most People Use It Like a Chainsaw.
The `noindex` meta tag tells Google: "Do not put this page in your search results." Simple.
But simple tools cause the most damage when misused.
When to Use Noindex
Thank-you pages after form submissions. Internal search results pages. Tag and category archive pages with thin content. Admin and login pages. Staging and development pages. Duplicate or near-duplicate content you cannot canonicalize.
Basically: any page that provides no value in search results.
When NOT to Use Noindex
Pages with backlinks pointing to them. You will lose that link equity.
Pages that get organic traffic. Obviously. But I have seen it happen.
Pages you have also blocked in robots.txt. If Googlebot cannot crawl the page, it cannot see the noindex tag. The page might stay indexed. This is the most common noindex mistake.
The Robots.txt + Noindex Trap
If you block a URL in robots.txt AND add a noindex tag to the page, the noindex tag will never be read because Google cannot crawl the page to see it.
Pick one or the other. Not both.
If you want to deindex a page: allow crawling, add noindex.
If you want to save crawl budget: block in robots.txt, but accept the page might stay indexed. Google's robots.txt documentation explains the difference between blocking crawling and blocking indexing.
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