# Frontend Development & UI Engineering

> Frontend development services: React interfaces engineered for accessibility, performance, and interaction, built as a design system in code. By Sentient Arc.

The layer users actually touch, engineered: React interfaces with real accessibility, performance budgets, and interaction quality, built as a design system in code.

## Users judge the render, not the repo
Nobody sees your architecture. They see the first paint, the layout that jumps, the button that lags, the flow that breaks on a real phone. The frontend is the entire product as far as the user is concerned.

And it is the easiest layer to fake and the hardest to get right: a screenshot looks finished while the accessibility, the performance budget, and the awkward states that decide real use go quietly unbuilt.

## Design systems in code, shipped to a budget
We build the interface as a system, not a pile of screens: reusable components, real tokens, and every loading, empty, and error state treated as a first-class part of the work.

Performance and accessibility are budgets we hold, not hopes: Core Web Vitals, keyboard and screen-reader paths, and interaction latency measured on real devices, not just a fast laptop.

## What we build
- **Component systems**: Reusable, tokenized component libraries that keep a growing product visually and behaviorally consistent.
- **Interaction & state**: Loading, empty, error, and edge states built as real UI, so the product holds up outside the happy path.
- **Performance engineering**: Core Web Vitals, bundle budgets, and render tuning, so the interface stays fast as features accrue.
- **Accessibility**: Keyboard, screen-reader, and contrast paths built in, so the product is usable by everyone and passes audit.

## Stack
- **Framework:** React, Next.js, TypeScript
- **Styling:** Tailwind CSS, CSS-in-JS, Design tokens
- **Quality:** Core Web Vitals, Accessibility (WCAG), Motion

## FAQ
**What do your frontend development services cover?**

The browser layer end to end: component systems, interaction and edge states, performance engineering, and accessibility, built as a design system in code rather than one-off screens.

**How is frontend engineering different from UI/UX design?**

Design decides what the interface should be; frontend engineering builds it to survive real data, real devices, and real load. We do both, but they are distinct disciplines with distinct deliverables.

**Can you build against our existing design system or Figma files?**

Yes. We implement to an existing system or Figma source of truth, and where none exists we build the component library and tokens as part of the work.

**Do you fix performance and accessibility on an existing frontend?**

Often, yes. A Core Web Vitals and accessibility audit usually finds the few changes that move the numbers, and we implement them rather than just handing over a report.

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Canonical page: https://www.sentientarc.com/capabilities/frontend-development