为什么我们使用.html代替.htm?

why do we use .html instead of .htm？

DOS was a massive operating system for PCs for a long time and it had a three-character limit on file extensions.

All HTML documents should have filenames that end with the extension .html unless the files reside on a DOS system, in which case they should have the extension .htm

DOS操作系统上文件后缀限制为3个字符，所以才会使用.htm的后缀，排除系统限制，所有的HTML文件应该使用.html的后缀名

参考：Why do we use .html instead of .htm? | CSS-Tricks