What senior frontend engineers actually do

A senior frontend engineer's day looks different from mid-level work. You're still writing code—lots of it—but you're also making architectural decisions that shape how a team ships features for months. You might spend a morning building a new component system in React, then shift to reviewing a junior engineer's pull request on performance optimization, then partner with design on why a particular interaction pattern won't work on mobile.

The core responsibility is owning the user-facing layer. That means translating product specs and design mockups into fast, accessible interfaces that users actually enjoy. But "owning" goes deeper than execution. You set the standards: which testing patterns the team follows, how the codebase handles state, what accessibility compliance looks like, how the frontend talks to the backend. You're the person who says "we're moving to Next.js for server-side rendering" or "we need a performance budget of 3 seconds for first contentful paint."

Mentorship is non-negotiable at this level. You're expected to grow the engineers around you. That means code review that teaches, not just approves. It means pairing with mid-level engineers on complex problems. It means being the person who can explain *why* a pattern matters, not just that it does.

The technical foundation

React and TypeScript are table stakes. Most postings expect deep fluency with React—hooks, component composition, state management patterns. TypeScript isn't optional; it's how teams prevent entire classes of bugs before they ship. You should be comfortable moving between class and functional components, understanding when to reach for context versus a state management library, and knowing the performance implications of your choices.

Next.js has become the de facto standard for React teams building full-featured products. You need to understand server-side rendering, static generation, API routes, and how to structure a codebase that scales. If you're not using Next.js, you're likely working with a similar framework (Remix, Astro) that solves the same problems.

CSS is not a afterthought skill. At the senior level, you understand CSS-in-JS tradeoffs, can debug layout issues without DevTools, and know when to reach for utility-first frameworks like Tailwind versus component-scoped styles. You're comfortable with responsive design, understand the cascade, and can optimize for bundle size.

Web performance is where seniority shows. You know how to profile a React app, identify bottlenecks, and ship faster experiences. That means understanding lazy loading, code splitting, image optimization, and how browser rendering works. You can explain why a re-render happened and how to prevent unnecessary ones. You know the difference between Time to Interactive and Largest Contentful Paint, and why both matter.

Accessibility isn't a feature you bolt on at the end. Senior engineers build it in from the start. That means semantic HTML, ARIA attributes used correctly, keyboard navigation, screen reader testing, and color contrast. It's not just compliance; it's about building products that work for everyone.

Testing is a multiplier on your impact. You write tests that catch real bugs, not just hit coverage targets. You understand the testing pyramid—unit tests for logic, integration tests for user flows, end-to-end tests for critical paths. You know when to mock and when not to. You can mentor others on what's worth testing and what isn't.

Hiring demand and compensation

There are 36 active postings for senior frontend engineers across 25 companies right now. That's a healthy, competitive market. Companies are actively hiring, which means you have leverage in negotiation and choice in where you land. The spread across 25 different companies—not concentrated in a few mega-employers—suggests the role is in demand across the industry, not just at FAANG.

Median compensation sits at $140k annually. That's the midpoint; some roles pay less, some significantly more, depending on company stage, location, and equity structure. At this level, total compensation usually includes equity or bonus, so the cash figure alone doesn't tell the full story. A Series B startup might offer $130k cash plus meaningful options; a larger company might offer $150k+ with a smaller equity grant.

How to get hired

Companies hiring for this role want to see a portfolio. GitHub repos matter, but so does a personal site or case study showing how you think about problems. Walk through a real project: what was the performance baseline, what did you change, what was the impact? How did you approach accessibility? What tradeoffs did you make and why?

In interviews, expect system design questions. You might be asked to architect a new feature from scratch—how would you structure the codebase, handle state, optimize performance, ensure accessibility? You'll likely do a take-home project or live coding session. The best candidates show their thinking, ask clarifying questions, and make intentional tradeoffs rather than reaching for the fanciest solution.

Be ready to talk about mentorship. How have you grown other engineers? What patterns have you introduced to a codebase? How do you approach code review? Senior roles are about multiplying impact through others, and companies want to see evidence of that.

Know the company's product and tech stack before you interview. If they're using Next.js and you've shipped a Next.js app, say so. If they care about accessibility and you've led accessibility audits, mention it. Specificity signals genuine interest.

What to look for in a role

The best senior frontend roles have a few things in common. First, you're not the only senior engineer on the team. You need peers to learn from and debate with. Second, the company actually cares about frontend. If the backend team makes all the architectural decisions and frontend is just implementing, you won't have the autonomy the role promises. Third, there's a real product—something users interact with daily—not an internal tool or a side project.

Ask about the codebase. How old is it? What's the test coverage like? How often do they refactor? A codebase that's been through multiple rewrites is a red flag; a team that's thoughtful about technical debt is a green one.

Ask about mentorship and growth. How many junior engineers are on the team? What's the promotion path? Do they invest in learning time? Senior roles should include time to level up the people around you, not just ship features.