iliakan/mime-types

When a web server sends a file to a browser, it includes a small label called a "content-type" that tells the browser what kind of file it is. This label determines whether the browser displays an image, plays a video, or formats text. The mime-types library is a tool for JavaScript developers that automatically figures out the correct label for any given file based on its name or extension. The library works by cross-referencing a file's extension, like .html or .json, against a built-in dictionary of known file types. It provides a few straightforward commands: a developer can ask it what label goes with a .json file, ask it to generate a complete, ready-to-use header for a markdown file, or even work backwards by asking what file extension corresponds to a specific content label. If a file extension isn't recognized, the tool simply returns "false" instead of guessing, which helps developers avoid accidentally sending the wrong information. This tool is designed for web developers who are building servers or applications that serve files to users. For example, if a user uploads a profile picture to a website, the developer uses this library to ensure the server correctly identifies that file as an image and sends it to the browser with the right instructions. It is particularly useful for anyone working with web frameworks like Express, as it handles the background plumbing required to serve documents, images, and other media seamlessly. A notable design choice is that this project is meant to be a simple, direct utility. Unlike some similar tools that might guess a file type or provide a generic fallback when they encounter an unknown extension, this one deliberately does not. It prefers to tell the developer "I don't know" so the developer can consciously decide how to handle the mystery file. It also allows teams to easily add their own custom file types if they are working with specialized formats.