How to get rid of .html in Magento URLs

Magento adds .html to category and product URLs by default. If you want to remove it, go to Backend – System – Config – Catalog – SEO tab, then delete .html from Product URL and Category URL suffixes.

Now, go to System – Index Management and reindex all data, plus clear your cache.

You can find more useful Magento tips at https://blog.amasty.com/how-to-fix-common-magento-issues/