A CFM file is a webpage that contains ColdFusion code, or CFML (ColdFusion Markup Language). It is dynamically executed by a ColdFusion web server when the page is accessed by a user. CFM files can run ColdFusion applications and scripts written in CFScript and may reference database information, generate forms, and create PDF reports on the fly.
You will most likely only encounter CFM files if you are a web developer and integrating ColdFusion functionality into your webpages. Developers typically use Adobe ColdFusion Builder for creating applications in CFML. However, they may use a variety of other CFML IDEs and editors, such as Adobe Dreamweaver, CFEclipse (plugin for Eclipse), and CFBrackets (extension for the Brackets source code editor).
CFM files can be opened and viewed with a source code editor, like Sublime Text or Visual Studio Code. The files can also be opened with a plain text editor, such as Micorost Notepad or Apple Textedit, which are bundled with Windows and macOS.
CFML is a tag-based language that features a syntax similar to HTML and XML. It includes unique tags and support for custom tags for creating dynamic web applications. All CFML tags begin with cf.
NOTE: ColdFusion was originally developed by Allaire, then later bought by Macromedia, and is now distributed by Adobe Systems after acquiring Macromedia in 2005.