Front-end

What a front-end developer needs to master at each stage of their career. From semantic markup to Core Web Vitals and component architecture — the concepts that come up in technical interviews and in everyday work, explained directly. Filter by level below.

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Mid-level

Web accessibility (a11y): ARIA, focus and contrast in practice

Accessibility is the front end's responsibility, not optional. ARIA in the right measure, keyboard focus, contrast and what really makes a difference.

Jun 25, 2026 Read

Junior

Semantic HTML and accessibility: the foundation that separates amateurs from professionals

Using the right tag isn't a detail: it's SEO, accessibility and maintainability. What semantic HTML is and why stacking divs for everything hurts you.

Jun 24, 2026 Read

Junior

CSS without fear: box model, flexbox and grid

Why elements have the size they have and how to position them. The box model and the two layout systems that solve 95% of cases.

Jun 22, 2026 Read

Junior

Essential JavaScript: types, scope and the DOM

The fundamentals behind every framework: types and coercion, var/let/const, closures and how JavaScript talks to the page.

Jun 20, 2026 Read

Mid-level

The event loop: how JavaScript does async without freezing

Single-threaded but non-blocking? Call stack, Web APIs, task queue and microtasks — the interview question that separates mid-level from junior.

Jun 17, 2026 Read

Mid-level

State in front-end: props, state and when to lift it up

What state is, the difference between props and state, unidirectional data flow and the famous 'lifting state up' without memorizing.

Jun 15, 2026 Read

Mid-level

Rendering and performance: reflow, repaint and the critical path

How the browser turns HTML/CSS/JS into pixels, what reflow vs repaint is and why your app lags — and what to do about it.

Jun 13, 2026 Read

Senior

Front-end architecture: componentization, design systems and monorepos

How to keep a large front end from turning into chaos: reusable components, design system, folder organization and the monorepo trade-off.

Jun 10, 2026 Read

Senior

Web performance: Core Web Vitals, lazy loading and bundle size

LCP, CLS, INP: the metrics Google measures and users feel. Code splitting, lazy loading and trimming the bundle to load fast.

Jun 8, 2026 Read

Senior

Front-end security: XSS, CSRF and CORS demystified

The three acronyms every senior front-end dev must explain: what each attack is, how the browser defends itself and what is your responsibility.

Jun 6, 2026 Read

Self-assessment: where are you?

Check what you already master. Your progress is saved in this browser only.

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Quiz: test what you learned

Four questions per level, with an explanation and the article that covers each topic. Ace a level and you can mark it in the self-assessment above.