A quiz is the quickest honest check of what you really know. It's easy to read a lesson and feel that everything makes sense, then find you can't remember the difference between let and const a week later. Answering questions without looking anything up shows you exactly which topics have stuck and which need another look.

Quizzes are also a form of practice in their own right. Every time you pull an answer out of memory, you make it easier to remember next time. That's why a short quiz after studying often does more for your memory than reading the same lesson twice.

What kind of questions to expect

The quizzes mix three types of question:

Multiple choice questions test concepts, such as which CSS property controls the space inside a border, or what a SQL JOIN returns.
True or false questions check common misunderstandings, the kind of thing beginners often get slightly wrong.
Code output questions show a short snippet and ask what it prints. These are the most useful of all, because they test whether you can actually read code.

Every question comes with an explanation. When you get one wrong, read the explanation before moving on. When you get one right, read it anyway; it often adds a detail the question didn't ask about.

Choosing a quiz

Each course has its own quiz page, such as the HTML quiz, the Python quiz or the SQL quiz. On a course quiz you can choose 5, 10 or 20 questions and narrow the questions to a single lesson, which is ideal right after you've finished that lesson. If you want a broader test, pick the full course and let the quiz shuffle questions from every topic.

The mixed web development quiz above pulls questions from all courses. It's a good warm-up before an interview, or a way to find out which language you've practised least.

How to use quizzes well

Take a short quiz straight after a lesson. Five questions is enough to confirm the main ideas went in.
Retake it a few days later. If your score holds, you've genuinely learned it. If it drops, revisit the lesson's examples and common mistakes.
Use keyboard shortcuts. Press the number keys to answer, which keeps you focused and makes longer quizzes quicker.
Don't chase a perfect score. A wrong answer tells you exactly where to spend your next ten minutes, which makes it more useful than a lucky right one.
Pair quizzes with practice. Quizzes check understanding, while exercises and projects build the skill of writing code. You need both.

Quizzes for interviews and exams

Many quiz questions mirror the questions asked in junior developer interviews and introductory exams: how the box model works, what == and === do differently, when to use a list or a tuple, what a primary key is. If you're preparing for either, work through the quiz for each relevant course and keep notes on anything you miss. The matching cheat sheet is a good companion for quick revision the night before.