React Foundation

used by 50m+ developers

100+ Enterprise Clients

Bring your next engineering challenge.

Work with engineers behind widely used open-source tools. We build and scale products across platforms, and help your teams deliver more with AI.

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Trusted by 100+ Enterprise clients

Expert Engineering

Build and scale React Native apps.

For over a decade, enterprise teams have trusted us with React and React Native products. Our senior engineers work with AI agents on new builds, complex migrations, and native engineering.

Feature Development

End-to-End Product Development

Architecture & Performance

Migrations & Upgrades

Enterprise Infrastructure

Team Training

Agentic Delivery

Turn AI into better software delivery.

From redesigning development workflows to building custom agents, testing their output, and choosing the right models, we turn AI into a practical part of product delivery.

AI SDLC Advisory

AI-Driven QA & Testing

Custom Agents

Custom & Private Models

From Startups to Fortune 500.

Faster message sending time

Expensify case study

React Foundation

Founding Member

300+ commits to React Native

Contributing since 2016

Case study

50M+

OSS downloads per month

100+

Enterprise clients

67K+

GitHub stars

Teamworks needed Module Federation, we helped make it real

Michael Song

Head of Platform

The trainers are always very helpful and supportive. It really makes a difference!

Artem Musiienko

Staff Eng

If you're looking for skilled and trusted React Native developers, Callstack is definitely the way to go.

Tom Occhino

Director of Engineering

Not only does Callstack have tremendously talented engineers, but I know they care about the success of the project as much as I do.

TC Davis

Product

The team at Callstack are the most experienced engineers in the React Native community.

Nader Dabit

Senior Developer Advocate

Their ability to deliver, and follow through, is unparalleled in the React Native ecosystem.

Matt Hargett

Principal Software Engineer

I recommend them as a trusted tech partner for running complex projects.

Jin Chung

Co-Founder, CTO

Their engineers proved to be a crucial part of our mobile app relaunch project.

Brian Aznar

Engineering Director

We had been struggling with React Native application performance until we met Callstack.

Huỳnh Chí Hùng

Associate Director

I appreciate their attention to detail, flexible approach and a high degree of expertise.

Glen Moriarty

Founder and CEO

min

From change to mini-app release

Teamworks case study

Case studies

See what experts and agents ship together.

Migrations & Upgrades

Architecture & Performance

Modernizing a Crypto Trading Platform With React Native and Self-Hosted OTA

increase in RN pages across the tracked page set

Custom Agents

AI-Driven QA & Testing

Architecture & Performance

Building an Agentic SDLC for a Web Launch in Under One Month

estimated delivery acceleration

AI-Driven QA & Testing

Engineering AI Loops for a Cross-Platform Design System

60+

components mapped with full Code Connect coverage

End-to-End Product Development

Enterprise Infrastructure

Accelerating Teamworks' Mobile Delivery With Re.Pack and Module Federation

min from code change to mini-app release

End-to-End Product Development

Feature Development

React Universe App: Networking Evolved With Liquid Glass

63%

adoption rate; majority of attendees registered in the app

Architecture & Performance

Migrations & Upgrades

AI-Driven QA & Testing

Migrating Questrade Edge Mobile to a Faster, More Scalable Architecture

33%

fewer re-renders across most features

Migrations & Upgrades

Enterprise Infrastructure

Migrating a Legacy React Native App to Expo for Faster Builds and Simplified Releases

faster builds after replacing Jenkins with EAS

Enterprise Infrastructure

Architecture & Performance

Building Scalable Observability for a High-Growth React Native App

3→1

analytics systems unified into a single interface

Team Training

Migrations & Upgrades

Architecture & Performance

Training HelloFresh Engineers to Build Production Apps With React Native

2.8x

increase in knowledge over 8 weeks (25% → 71% assessment scores)

Feature Development

End-to-End Product Development

Building a browser-based React Native playground for Expo

Migrations & Upgrades

End-to-End Product Development

Enterprise Infrastructure

Migrating iOS and Android Apps to React Native for AutoZone

growth in mobile user base during the migration period

Architecture & Performance

End-to-End Product Development

Optimizing Android TV Startup for Global Streaming Platform

faster startup time on FireTV and FireHD devices

End-to-End Product Development

Enterprise Infrastructure

Architecture & Performance

Launching a High-Performance React Native App on Samsung TV

platforms under one RN codebase: tvOS, FireTV, Tizen, LG, Vizio

Feature Development

Architecture & Performance

Migrating AutoZone’s Storefront to Next.js for Better Performance and SEO

SEO rank, recovering from 3-9

Architecture & Performance

AI-Driven QA & Testing

Enterprise Infrastructure

Enhancing Application's Performance for Expensify

faster message sending time

Architecture & Performance

End-to-End Product Development

Improving Chat Performance and Creating a Custom UI Library for Dream11

78%

bundle size reduction (from 50 MB to 11 MB)

Architecture & Performance

Feature Development

Creating React Native SDK Wrapper for Rive

100k

weekly downloads on npm

End-to-End Product Development

Feature Development

Team Training

Enhancing Performance of Momo's Super App With Re.Pack

Migrations & Upgrades

Feature Development

End-to-End Product Development

Modernizing 7Cup's React Native Codebase and Adding Platform Features

130%

increase in users post-upgrade

End-to-End Product Development

Feature Development

Launching White-Label Super App for Zephyr Cloud With Re.Pack

Clients

Trusted by enterprise teams at scale.

Teamworks needed Module Federation, we helped make it real

Michael Song

Head of Platform

We had been struggling with React Native application performance until we met Callstack.

Huỳnh Chí Hùng

Associate Director

The trainers are always very helpful and supportive. It really makes a difference!

Artem Musiienko

Staff Eng

Not only does Callstack have tremendously talented engineers, but I know they care about the success of the project as much as I do.

TC Davis

Product

I appreciate their attention to detail, flexible approach and a high degree of expertise.

Glen Moriarty

Founder and CEO

I recommend them as a trusted tech partner for running complex projects.

Jin Chung

Co-Founder, CTO

Their engineers proved to be a crucial part of our mobile app relaunch project.

Brian Aznar

Engineering Director

EXPERT ENGINEERING · AGENTIC DELIVERY

Put our expertise to work.

Our engineers can join your team, take on a defined project, or help you adopt agents across development, testing, and release. Tell us what you're working on.

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Insights

Worth your time, by engineers.

Article

6/8/2026

React Native Wrapped 2025: A Month-by-Month Recap of The Year

The first edition of React Native Wrapped looks back at the year RN turned 10 and the ecosystem doubled down on the New Architecture. It provides a month-by-month record of 2025, covering major framework releases, the Legacy Architecture freeze, React 19 integration, and notable developments across tooling, performance, styling, native modules, Expo, and platform adoption.

Event

11/17/2026

Efficient On-Device LLMs in React Native Done Right

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Podcast

9/7/2026

Running AI in the Browser With Transformers.js

Webinar

7/21/2026

Behavior Review for AI-Native Delivery

Article

9/17/2026

Exploring Jev for AI-Driven QA with agent-device

Explore Insights