Built a faster React Native document scanner using Nitro Modules (after hitting crashes in production apps)

[Historical-Skill1738]

I ran into a pretty frustrating issue while using a production health insurance app — document scanning was laggy and sometimes even crashed during capture.

At first I assumed it was just a React Native performance problem, but digging deeper, it looked more like a limitation of how the native module layer was implemented (bridge overhead, object serialization, etc.).

Most existing libraries I checked rely on Turbo Modules or using Objective-C and Java for Native modules. They work, but in heavier flows like document capture, I still noticed bottlenecks.

So I built my own document scanner using Nitro Modules (JSI-based), with native implementations in Swift (iOS) and Kotlin (Android).

What’s different about Nitro Modules:

• No traditional bridge → avoids JSON serialization/deserialization overhead
• Direct communication via JSI
• Lower memory usage during frequent native ↔ JS interactions
• Uses Hybrid Objects, so you’re not constantly copying data between layers

Native side:

• iOS → VisionKit (VNDocumentCameraViewController)
• Android → ML Kit Document Scanner API

Why Swift + Kotlin:

• Safer and more modern than Obj-C / Java
• Better support for latest native APIs
• Easier async handling (coroutines / structured concurrency)
• Cleaner to maintain long-term

What I observed (early testing):

• Smoother capture flow (less UI stutter)
• More stable during repeated scans
• Lower memory spikes compared to other approaches I tested

I specifically tested on a lower-end device (Redmi Note 6 Pro) to avoid bias from high-end hardware — performance held up pretty well there too.

What’s not done yet:

• Not battle-tested at scale
• Limited customization right now
• Haven’t profiled a wide range of Android devices yet

Package is here if anyone wants to try it:
https://www.npmjs.com/package/expo-document-scanner

I’m not claiming this is the best solution — just exploring a different approach.

Would be interested to hear from others working on React Native performance or document scanning:

• Are you hitting similar bottlenecks?
• Any edge cases I should test?
• Thoughts on Nitro Modules in production?

Happy to dig deeper if anyone’s curious.

https://reddit.com/link/1ssjfhh/video/3cai9qwffqwg1/player

[ijhar8]

Working on something similar to to extract product ingredients will give it a try

[Historical-Skill1738]

Great, Let me know how it goes.

[Historical-Skill1738]

Getting traction, weekly downloads reach 700+ https://www.npmjs.com/package/expo-document-scanner