SWF, or Small Web Format, is a file format used for multimedia, vector graphics, and ActionScript. Originally developed by Macromedia and later acquired by Adobe, SWF files are commonly used for animations, interactive content, and web applications. They can be embedded in web pages and are designed to be lightweight and efficient for online use. SWF files are typically created using Adobe Flash or similar software, allowing developers to create rich internet applications. However, with the decline of Flash support in modern web browsers, the use of SWF has significantly decreased, leading to a shift towards other technologies like HTML5 for web-based animations and interactivity.