You might have seen web pages named something like index.html or about.htm. Both of these are HTML files that web browsers use to display web pages to users. But what’s the difference between the .html and .htm file extensions?

Back in the day—before Windows 95—older DOS-based operating systems followed something called the 8.3 filename format. That meant a file name could only be up to 8 characters long, with a 3-character extension. Because of this, .htm was used for HTML documents.

However, once Windows 95 came along, that limitation was removed. From then on, people gradually started using .html more frequently. Today, .html has become the standard extension in most web development projects.

That said, .htm files still work perfectly well. Modern web browsers and servers recognize both extensions equally. Even when it comes to search engine optimization (SEO), there’s no real difference—search engines can index both .html and .htm pages just the same.

In today’s collaborative and often large-scale development environments, consistency and clarity in file naming are really important. That’s why most developers now prefer using the .html extension—it helps keep things clean, consistent, and easier to manage.