Borderlands 4 Reverse Engineering Guide
1 Borderlands 4 Reverse Engineering Guide
Zero to Hero
A comprehensive guide to understanding game internals, reverse engineering techniques, and using the bl4 tooling to analyze and modify Borderlands 4.
1.1 Chapters
1.1.1 Part I: Core Concepts
| Chapter | Title | Description |
|---|---|---|
| 1 | Binary Basics | Hexadecimal, endianness, data types, and memory layout |
| 2 | Unreal Engine Architecture | UObjects, reflection system, pak files, and usmap |
| 3 | Memory Analysis | Process memory, dumps, pattern scanning, pointer chains |
1.1.2 Part II: Game Formats
| Chapter | Title | Description |
|---|---|---|
| 4 | Save File Format | Encryption, compression, YAML structure, key derivation |
| 5 | Item Serials | Base85 encoding, bit manipulation, token parsing |
| 6 | NCS Format | Nexus Config Store: compression, content format, binary section |
1.1.3 Part III: Practical Application
| Chapter | Title | Description |
|---|---|---|
| 7 | Data Extraction | Pak files, NCS parsing, memory dumps, manifest generation |
| 8 | Parts System | Part categories, compositions, licensed parts, validation |
| 9 | Using bl4 Tools | Complete CLI reference and practical workflows |
1.1.4 Appendices
| Appendix | Title | Description |
|---|---|---|
| A | SDK Class Layouts | Memory layouts for UObject, AOakCharacter, AWeapon, etc. |
| B | Weapon Parts Reference | Complete catalog of weapon parts by manufacturer |
| C | Loot System Internals | Drop pools, rarity weights, luck system |
| D | Game File Structure | Full asset tree and file organization |
1.1.5 Reference
| Title | Description | |
|---|---|---|
| Glossary | Terms, definitions, and quick reference tables |
1.2 Quick Start
New to reverse engineering? Start with Chapter 1: Binary Basics and work through sequentially.
Want to edit saves? Jump to Chapter 4: Save File Format.
Need to decode an item? See Chapter 5: Item Serials.
Interested in the NCS format? See Chapter 6: NCS Format for the complete format specification.
Just want the tool reference? Go to Chapter 9: Using bl4 Tools.
1.3 Prerequisites
Before starting, ensure you have:
- Basic programming knowledge (any language)
- Command line familiarity
- Rust toolchain installed (rustup.rs)
- The bl4 repository cloned and built
git clone https://github.com/monokrome/bl4
cd bl4
cargo build --release1.4 About This Guide
This guide accompanies the bl4 project—a Borderlands 4 save file editor and item serial decoder. It documents not just how to use the tools, but why they work, giving you the knowledge to explore further on your own.
Each chapter includes:
- Concept explanations with visual diagrams
- Practical examples you can try immediately
- Exercises to test your understanding
- Tips from real reverse engineering sessions
For the latest version of this guide, visit book.bl4.dev