Overview

URL Encoding Course

Understand percent-encoding, query strings, and the difference between encodeURI and encodeURIComponent.

This course explains percent-encoding (URL encoding)—how text becomes safe inside URLs, query strings, and path segments. The focus is the encoding model (bytes, reserved characters, decoding rules), not a step-by-step manual for any single website.

Who this course is for

  • Backend and frontend developers who build links, APIs, or redirects
  • Anyone debugging “broken” URLs with spaces, emojis, or & inside values
  • Engineers comparing encodeURI, encodeURIComponent, and form submissions

What you will learn

  1. Why URLs treat some characters as special and how encoding fixes that
  2. How %XX maps to bytes (including UTF-8 for non-ASCII text)
  3. When to use encodeURI versus encodeURIComponent in JavaScript
  4. How query strings (?a=1&b=2) are formed and parsed safely
  5. Why + and %20 interact differently in query strings and HTML forms

How to use this course

Use the table of contents to move between lessons. Read the overview first, then follow the lessons in order—each one assumes the previous ideas.

If you want to experiment after a lesson, the related URL encoder/decoder tool is optional; the goal here is to understand the rules, not memorise one UI.

Start lesson 1