When i visit my plain url of website its working but in end when i add .html its also working but making dublicate errors and affecting seo how to fix it

[nathanmartin]

@Aliff34 This is standard Netlify behavior:

Netlify pretty urls won't strip .html extension

There is no way to prevent us from serving the .html URL if someone types it in. The idea is, you don’t publish that URL, nobody finds it, and thus you have no duplicate content problems. The Pretty URL’s feature just REWRITES your html and js and css to link to /file instead of /file.html. We’ll still serve both, with or without the feature enabled.

A solution is to specify the canonical url:

How to remove duplicate URL from Google Search? (indexed all *.html urls by accident)

You should have a canonical URL on each of your pages. Read here: 網址標準化和標準標記 | Google 搜尋中心  |  說明文件  |  Google Developers. Then, even if Google sees duplicate pages, it won’t be a problem. As for what you can do for now is, try to remove the duplicate pages from Search Console.

Another option would be Edge Functions:

Disabled Pretty URLS but .html-less links continue to work and be indexed by search engines

You can use Edge Functions to handle this: but not with simple _redirects.