React Native Patch Updates — Delta & File-Level Diffing Explained Guide
Patch updates represent a fundamental shift in how React Native apps receive over-the-air updates. Instead of downloading entire bundles, patch updates use delta and file-level diffing to ship only what changed—resulting in updates that are 90-98% smaller and 10-20× faster.
This guide explains how patch updates work, why they matter, the technical architecture behind differential updates, and why legacy solutions like CodePush cannot support this technology.
This guide is for teams asking things like: How do patch updates work technically? Why can't CodePush support patches? What's the difference between delta and file-level diffing? How much smaller are patch updates? Can we achieve 90-98% size reduction?
What You'll Learn
- • What patch updates are and how they differ from full bundles
- • Why patch updates matter for mobile apps
- • How patch updates work (step-by-step technical process)
- • Types of patch updates (delta, file-level, asset patching)
- • Performance benchmarks and size comparisons
- • Why CodePush cannot support patch updates
- • Best practices and security considerations
- • CI/CD integration for automated patch generation
Introduction — What Are Patch Updates?
Patch updates are differential updates that contain only the changed files or bytes between two versions of your React Native app. Unlike full bundle updates that replace the entire JavaScript bundle, patch updates use binary diffing algorithms to generate minimal patches containing only what changed.
Full Bundle Updates
- Downloads entire bundle (2-5 MB typical)
- Replaces all JavaScript code
- Slow downloads on slower connections
- High bandwidth usage
- Used by CodePush and traditional OTA systems
Patch Updates
- Downloads only changed content (50-500 KB typical)
- Merges changes with existing bundle
- Fast downloads even on slow connections
- 90-98% smaller than full bundles
- Available in modern OTA systems like React Native Stallion
Example: If you fix a bug in a single component (changing 50 lines of code), a full bundle update would require downloading the entire 20 MB bundle. A patch update would only download the 50 changed lines, resulting in a 400 KB patch—98% smaller.
Why Patch Updates Matter in Mobile Apps
Bandwidth Efficiency
Mobile users often have limited data plans or slower connections. Patch updates dramatically reduce bandwidth usage, making updates feasible even on cellular networks. For apps with millions of users, this translates to significant cost savings and better user experience.
Faster Startup Time
Smaller patches download and install faster, reducing the time users wait for updates. Updates that previously took 30-60 seconds now complete in 1-2 seconds, improving app startup time and user satisfaction.
App Reliability
Faster updates mean critical bug fixes reach users immediately. When a production issue is discovered, patch updates enable instant hotfixes without waiting for app store approval or forcing users to download large bundles.
How Patch Updates Work (Step-by-Step)
Hashing
The system generates cryptographic hashes (SHA-256) for each file in both the old and new bundles. These hashes identify which files have changed, been added, or removed.
Comparing Diffs
Binary diff algorithms compare the old and new bundles at the file level. Changed files are identified, and only the modified bytes are extracted. Unchanged files are excluded from the patch.
Building Patch Bundles
The system creates a patch bundle containing only changed files, metadata (version info, file mappings), and instructions for merging. The patch is compressed and signed for security.
Downloading Patch
The app downloads the patch from the OTA service. Since patches are 90-98% smaller than full bundles, downloads complete in seconds instead of minutes.
Merging on Device
The app verifies the patch integrity, then merges the patch with the existing bundle. Changed files are replaced, new files are added, and deleted files are removed. The merged bundle is validated before use.
Types of Patch Updates
Delta Patch
Binary-level diffs that identify changed bytes within files. Most efficient for small code changes, reducing update size by up to 99% for minor modifications.
File-Level Diff Patch
Identifies entire files that changed and includes only those files in the patch. More efficient than full bundles but less granular than delta patches. Ideal for component-level changes.
Asset Patching
Updates images, fonts, and other assets independently of JavaScript code. Changed assets are replaced, while unchanged assets remain untouched.
Monolith vs Modular Patching
Monolith: Single bundle patching (traditional approach). Modular: Patches individual modules or chunks separately, enabling even more granular updates for large applications.
Patch Updates vs Full Bundle Updates
| Aspect | Full Bundle Updates | Patch Updates |
|---|---|---|
| Update Size | 2-5 MB | 50-500 KB (90-98% smaller) |
| Download Time | 30-60 seconds | 1-2 seconds |
| Bandwidth Usage | High | Minimal |
| User Experience | Noticeable wait time | Instant, seamless |
| Adoption Rate | Lower (users wait for Wi-Fi) | Higher (instant adoption) |
| Technology | Full bundle replacement | Binary diffing, file-level patching |
Patch Update Architecture
The patch update flow involves multiple components working together:
Patch Updates in React Native
Metro Bundler Integration
Metro bundler creates the JavaScript bundle that serves as the source for patch generation. The bundler's output structure (modules, chunks, assets) determines how patches are generated and applied.
React Native Asset System
React Native's asset system (images, fonts, etc.) is patchable independently of JavaScript code. Changed assets can be updated without touching JavaScript bundles, further reducing patch sizes.
JavaScript Bundle Structure
Modern React Native bundles are structured as modules and chunks. Patch updates can target individual modules, enabling granular updates that only touch changed components or features.
Why CodePush Cannot Do Patch Updates
CodePush was built before patch update technology became standard. Its architecture has fundamental limitations that prevent patch support:
Legacy Architecture
CodePush was designed for full bundle replacement only. Its core architecture doesn't include diffing algorithms or patch generation capabilities.
No Binary Diffing
CodePush lacks the binary diffing technology required to compare bundles and generate patches. It can only serve complete bundles.
No Merging Logic
CodePush doesn't have the merging logic needed to apply patches to existing bundles. It only supports full bundle replacement.
Maintenance Status
CodePush is effectively unmaintained, so even if patch support were technically feasible, it won't be added. The hosted service has been shut down, and development has stopped.
Performance Benchmarks
Real-world performance data showing the dramatic difference patch updates make:
| Change Type | Full Bundle Size | Patch Size | Reduction |
|---|---|---|---|
| Small Bug Fix (50 lines) | 20 MB | 50 KB | 99.75% smaller |
| Component Update | 20 MB | 150 KB | 99.25% smaller |
| Feature Addition | 20 MB | 800 KB | 96% smaller |
| Large Refactor | 20 MB | 2 MB | 90% smaller |
Best Practices for Patch Updates
Security & Integrity
Hashing
Patches are hashed using SHA-256. The app verifies patch hashes before merging to ensure integrity and detect corruption or tampering.
Signing
Patches are cryptographically signed using RSA or ECDSA keys. Signature verification ensures patches come from trusted sources and haven't been modified in transit.
Integrity Checks
After merging, the resulting bundle is validated. If validation fails, the patch is rejected and the app continues using the previous version, with automatic rollback if configured.
CI/CD Integration
Automate patch generation and upload in your CI/CD pipeline:
# GitHub Actions Example
- name: Build bundle
run: npx react-native bundle --platform android
- name: Upload bundle
run: npx stallion publish-bundle \
--upload-path=org/project/bucket \
--platform=android
# Patch is automatically generated
# when promoting the releaseModern OTA systems automatically generate patches when you upload a new bundle version. The system compares the new bundle with the previous version and creates a patch automatically—no additional configuration required.
Tools That Support Patch Updates
React Native Stallion
React Native Stallion is the only React Native OTA tool that offers real delta patching and file-level diffing. It provides:
- Automatic patch generation (90-98% size reduction)
- File-level differential updates
- Binary diffing algorithms
- Automatic merging and validation
- Comprehensive patch analytics
- Zero configuration required
Note: There is literally no other React Native tool offering real delta patching. CodePush, Expo Updates, and other OTA solutions only support full bundle updates.
What happens to cost when your app scales
Here's the math: You've got a React Native app with 700k active users. Your bundle is 16MB. With full bundle updates, every release means 700k users downloading 16MB each—that's 11.2TB per release. If you ship 5 updates per month, you're looking at 56TB monthly CDN traffic.
Patch updates change that completely. Instead of 16MB, you're shipping maybe 350KB. Same 700k users, but now it's 245GB instead of 11.2TB. That's 98% less bandwidth. The real win is user experience—users on slower connections actually get the update instead of timing out.
The infrastructure cost drops too. If you're self-hosting, your CDN bill goes way down. If you're using a hosted service, patch updates mean lower per-gigabyte costs. More importantly, your infrastructure can handle the load without scaling issues, even during peak release times.
Conclusion
Patch updates represent the future of React Native OTA updates. By shipping only what changed, patch updates deliver updates that are 90-98% smaller, 10-20× faster, and dramatically improve user experience.
While legacy solutions like CodePush cannot support patch updates due to architectural limitations, modern OTA systems like React Native Stallion provide automatic patch generation, file-level diffing, and seamless integration with existing workflows.
If you're looking to reduce update sizes, improve adoption rates, and deliver faster updates to your users, patch updates are essential. React Native Stallion is the only platform offering this technology for React Native apps today.
Read the Complete Guide
For detailed implementation guides, early access information, and real-world examples, check out our comprehensive blog post:
Patch Updates for React Native — Modern CodePush Alternative with 95% Smaller OTA UpdatesReady to Experience Patch Updates?
Start using React Native Stallion today and experience updates that are 90-98% smaller and 10-20× faster than traditional OTA solutions.
Related Resources
Frequently Asked Questions
How do patch updates work technically?
Patch updates use delta and file-level diffing to compare the old bundle with the new one. Only changed files are included in the patch. The SDK downloads the patch, verifies it, and applies it to the existing bundle on the device.
Why can't CodePush support patches?
CodePush's architecture stores bundles as opaque blobs. It doesn't have the ability to diff bundles or generate patches. It can only deliver full bundles. Modern OTA systems need to understand bundle structure to generate patches.
What's the difference between delta and file-level diffing?
Delta diffing compares byte-level changes within files. File-level diffing compares entire files and only includes changed files in the patch. Most patch systems use a combination—file-level for efficiency, delta for files that changed.
How much smaller are patch updates?
Typically 90-98% smaller than full bundles. A 15MB bundle might become a 200-500KB patch depending on what changed. Small bug fixes are often under 100KB. Large feature additions might be 1-2MB, still much smaller than the full bundle.
What happens if an OTA update crashes the app?
React Native Stallion has automatic rollback that detects crashes and reverts to the previous working version. If the app crashes on startup, it won't get stuck—the SDK rolls back automatically before users notice.
Are patch updates secure?
Yes, if implemented correctly. React Native Stallion signs patches cryptographically and verifies integrity before applying them. The patch generation and application process is tamper-proof.