1. FRONTEND MENTOR

Solve real-world HTML, CSS, and Javascript challenges, whilst working with professional design.

Link: frontendmentor.io

2. TREEHOUSE

Treehouse is a great platform to help you learn certain languages like Javascript or even backend languages like PHP. You can use their in-demand courses which have a wide variety of quizzes and challenges or go through the track which has a guided curriculum to teach you something specific.

Link: teamtreehouse.com

3. CSSBattle

This one is specific to CSS, but its gamification system is a great way to track your progress and continue learning, they even give away some merchandise at the end of some battles, which is always a great motivator.

Link: cssbattle.dev

4. CODEPEN CHALLENGES

The great thing CodePen challenges is that they provide prompts for nearly a variety of languages and technology. HTML, CSS, JavaScript, Flutter, you name it. What's even better is that you get to share your solution with everyone who participated in the challenges, and give, and receive feedback on your solution.

Link: codepen.io/challenges

5. JAVASCRIPT 30

A 30-day vanilla JS coding challenge by Wes Bos. You get to build clocks, drum kits, and so much more just using Javascript. It's also free, so there's no excuse to not sign up and get started right away!

Link: javascript30.com

6. CODEWELL

If you want to level up your HTML, CSS, and JavaScript skills, Codewell offers real-world Figma templates that you can use to improve. You can even share your solution and receive feedback on either the website or on the growing Stack community.

Link: codewell.cc

Inspiration (twitter.com/imAlfaiz/status/155544098949746..)