Build modern web apps that scale across platforms
We help product teams build high-performance web applications with React—designed to evolve, extend, and support cross-platform expansion. Start with the web, scale to anything.
Why React is still the best way to build for the web
React powers today’s most ambitious web products. It’s flexible, fast, and supported by an ecosystem that keeps moving forward—ideal for building once and scaling over time.
Battle-tested performance
React powers the world’s top web apps—optimized rendering, smart diffing, and smooth UI are baked in.
Battle-tested performance
React powers the world’s top web apps—optimized rendering, smart diffing, and smooth UI are baked in.
Cross-platform ready
Build once with React, then bring your product to native, desktop, or embedded environments when you're ready.
Cross-platform ready
Build once with React, then bring your product to native, desktop, or embedded environments when you're ready.
Flexible for the future
From MVP to multi-platform scale, React supports product evolution without framework rewrites or rigid opinions.
Flexible for the future
From MVP to multi-platform scale, React supports product evolution without framework rewrites or rigid opinions.
Building high-performance storefront for AutoZone with Next.js
AutoZone sought to boost their web app’s performance and SEO. We migrated their custom server-side rendering setup to Next.js, improving performance metrics and simplifying development.
200%
Better application performance
5x
Faster refresh time in development
Web app that meets today’s standards—and tomorrow’s platforms
Built to grow, not just work. From code quality to team handoff, every layer is designed to scale across platforms and teams.
Production-ready foundations
Typed code, scalable file structure, and best-practice setup using modern React tooling.
High-performance
Optimized load time, rendering, and interactivity—your app feels fast everywhere.
Designed for platform expansion
Codebase built to evolve—ready to extend to native, desktop, or any other surface.
Top-notch CI/CD
CI/CD, staging environments, preview links, and testing—built in from day one.
Component system
Reusable UI architecture, design tokens, and structure that makes it easy to grow or redesign later.
Owned by your team
Built with handoff in mind—clear structure, documentation, and naming conventions so your team can take full ownership.
Build modern web apps—or take them further
Build a new web application
Design and deliver modern React apps—from internal dashboards to user-facing SPAs and full-stack products. Built with scalable architecture, modular components, and CI/CD from day one.
Modernize existing web application
Refactor aging apps for performance, maintainability, and compatibility with modern workflows. Transition to frameworks like Next.js without pausing delivery.
Add a new platform to your stack
Take your codebase cross-platform—adapting it to run natively with React Native or on desktop with Electron, while maintaining a shared architecture.
Why leading companies work with Callstack
Meta Official Partners
We are official Meta partner for React Native, co-organizers of React Conf and hosts of React Universe Conf.
Working at scale
We know how to make React Native work at enterprise scale, both technically and organizationally.
React Native Core Contributors
We don’t just use React Native to build cross-platform apps, we help shape it for millions of developers.
Team at scale
We’re a team of 200+ engineers ready to start fast and scale with your needs.
Enterprise-friendly
We hold ISO certifications and follow strict security standards to make onboarding smooth and compliant.
Wide range of services
As a partner for your full application lifecycle, we offer a full range of services around React and React Native.
FAQs
Building a web app isn’t just about writing code—it’s about making the right decisions early, so your product is fast, scalable, and future-ready. Here’s what teams usually ask us before we start.
We build modern web applications that are fast, scalable, and easy to evolve—ranging from B2B platforms to customer-facing products and internal tools.
React gives us the flexibility to build high-performance apps that are maintainable over time. It's supported by a strong ecosystem and works well across different devices and environments.
We use techniques like server-side rendering, lazy loading, and performance profiling to ensure fast load times. SEO is built into the architecture, not added as an afterthought.
Your app will be built in a way that makes it easy to extend to native mobile, desktop, or even embedded platforms—using the same core code and structure.
Yes. We adapt to your stack and workflows. Our focus is on setting you up with clear structure and documentation so your team can take over easily.
Absolutely. We can create a design system from scratch or expand what you have, using token-based components and scalable architecture.
We can usually begin within a few days. Our process is flexible and designed for fast onboarding.
Need a partner to build or scale your web app?
We help teams design and deliver high-performance web apps with a strong foundation—built to evolve across platforms, teams, and user needs.
