Key difference: HTML stands for HyperText Markup Language. It is a well known mark up language used to develop web pages. It has been around for a long time and is commonly used in webpage design. .htm and .html are two ways to save a HTML file. Both are essentially the same thing. There is actually no difference between .htm and .html, except for the number of characters used.

HTML stands for HyperText Markup Language. It is a well known mark up language used to develop web pages. It has been around for a long time and is commonly used in webpage design. XML or Extensible Markup Language defines a set of rules for encoding documents in a format that can be read by both, human and computer.

HTML is written using HTML elements, which consist of tags, primarily and opening tag and a closing tag. The data between these tags is usually the content. The main objective of HTML is to allow web browsers to interpret and display the content written between the tags. The tags are designed to describe the page content. HTML comes with predefined tags. They allow one to insert images, text, videos, forms and other pieces of content together into a cohesive webpage.

Elements of HTML are the basic building blocks of all websites. HTML allows images and objects to be embedded in the webpage. It can also be used to create interactive forms. HTML also provides the means to create structured documents. It does this by denoting structural semantics for text such as headings, paragraphs, lists, links, quotes and other items. However these days, web pages are rarely designed using only HTML. HTML allows for the programmer to embed scripts written in languages such as JavaScript, which many often do. This changes the look and behavior of the HTML web pages.

.htm and .html are two ways to save a HTML file. Both are essentially the same thing. There is actually no difference between .htm and .html, except for the number of characters used.

The reason for the different file extensions dates back to the early versions of Windows. The original file extension for the HTML file was ‘.html’; however in Windows all files required a three letter file extension. So, the file extension was shortened to ‘.htm’. However, Macintosh was not limited to three letter file extensions, so Mac users used ‘.html’. Eventually, with upgrades Windows also began to accept ‘.html’. However, many users were already used to ‘.htm’, so both the three letter file extension and the four letter extension began to be commonly used, and still is. However, there are cases where some servers program their default directory to support only .html files. Hence, .htm files are not supported on those servers.

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