An URL encoder is a tool or utility that converts special characters in a URL into a format that can be transmitted over the Internet. URLs can only be sent over the Internet using the ASCII character set, so characters like spaces, punctuation, and non-ASCII characters must be encoded to avoid confusion and ensure proper data transmission.

For example, spaces are replaced with %20, and special characters like #, &, and ? are represented by their respective percent-encoded values. This ensures that the URL remains intact and behaves as expected when accessed by browsers and web servers.

URL encoding is often used in web development when constructing query strings, submitting form data, or embedding URLs within HTML or JavaScript code. It helps prevent issues related to invalid characters and ensures compatibility across different web technologies.

In summary, a URL encoder plays a crucial role in making URLs safe and functional for web communication by transforming potentially problematic characters into a standard format.