URL Encoding: A Complete Guide for Web Developers
URLs are the foundational communication mechanism of the web. However, certain special characters within a URL—such as `&`, `?`, `#`, and `/`—have specific meanings. When you need to use these characters as data, you must **percent-encode** them correctly to avoid broken links, security vulnerabilities, and data loss across services. In this guide, we'll cover the difference between encoding query parameters and path segments and how to handle this process correctly.
APIs and Web Apps
When encoding a URL, you should differentiate between two main functions: **encodeURIComponent** and **encodeURI**. The **encodeURIComponent** function is used to encode a specific component of a URL, such as a query parameter. It encodes all special characters that could cause issues across services. **encodeURI**, on the other hand, is used to encode an entire URL and preserves characters that define the URL's structure, such as `/`, `?`, and `&`. You should never double-encode a value.
Important Tips
- Always use **
encodeURIComponent** when encoding query parameter values (e.g., `q=hello world`). - Use **
encodeURI** when encoding an entire URL, for example, when sanitizing a URL entered by a user. - If you're using **Unicode** characters, consider normalization before encoding to avoid mismatched encodings across different services.
To verify how browsers and servers interpret your URLs, you can use the URL Encoder/Decoder tool. This allows you to interactively test how different values are encoded and catch potential errors early.