bl4

Features

• Decrypt and encrypt .sav files using Steam ID
• Interactive editing via $EDITOR
• Query and modify save data (level, currencies, XP, etc.)
• Decode item serial numbers (weapons, equipment, etc.)
• Hash-based backup system
• Optional Steam ID configuration
• WebAssembly support for JavaScript/TypeScript
• Rust library with CLI wrapper

Installation

cargo install bl4-cli

From source:

git clone https://github.com/monokrome/bl4.git
cd bl4
cargo build --release -p bl4-cli

Binary location: target/release/bl4

JavaScript/TypeScript (NPM):

npm install bl4

Usage

Configuration

bl4 configure --steam-id 76561197960521364
bl4 configure --show

Steam ID is required for encryption/decryption. Find it in your Steam account page.

Editing

bl4 edit -i 1.sav
bl4 edit -i 1.sav -s 76561197960521364  # Override configured Steam ID

Querying

bl4 get -i 1.sav
bl4 get -i 1.sav --level
bl4 get -i 1.sav --money
bl4 get -i 1.sav --info
bl4 get -i 1.sav "state.currencies.cash"
bl4 get -i 1.sav "state.experience[0].level"

Modifying

bl4 set -i 1.sav "state.experience[0].level" 50
bl4 set -i 1.sav "state.currencies.cash" 999999
bl4 set -i 1.sav "state.currencies.eridium" 50000
bl4 set -i 1.sav --raw "state.some_field" "{complex: yaml, structure: [1, 2, 3]}"

Automatic backups enabled by default (--backup flag).

Decryption

bl4 decrypt -i 1.sav -o save.yaml
bl4 decrypt -i 1.sav > save.yaml

Encryption

bl4 encrypt -i save.yaml -o 1.sav
cat save.yaml | bl4 encrypt > 1.sav

Inspection

bl4 inspect -i 1.sav
bl4 inspect -i 1.sav --full

Item Serial Decoding

bl4 decode '@Ugr$ZCm/&tH!t{KgK/Shxu>k'
bl4 decode '@Uge8jxm/)@{!gQaYMipv(G&-b*Z~_' --verbose

Decodes BL4 item serial numbers to show:

• Item type (weapon, equipment, utility, etc.)
• Raw decoded bytes
• Parsed tokens (VarInt, VarBit, Part structures)
• Extracted fields (manufacturer, rarity, level when available)

Backup System

Hash-based tracking with .sav.bak and .sav.bak.json metadata:

• First edit creates backup
• Subsequent edits preserve original
• File replacement triggers new backup

Library Usage

[dependencies]
bl4 = "0.1"

use bl4::{decrypt_sav, encrypt_sav, SaveFile};
use std::fs;

let encrypted = fs::read("1.sav")?;
let yaml_data = decrypt_sav(&encrypted, "76561197960521364")?;
let mut save = SaveFile::from_yaml(&yaml_data)?;

println!("Character: {:?}", save.get_character_name());
println!("Cash: {:?}", save.get_cash());

save.set_cash(999999)?;
save.set_character_name("NewName")?;

let modified_yaml = save.to_yaml()?;
let encrypted = encrypt_sav(&modified_yaml, "76561197960521364")?;
fs::write("1.sav", encrypted)?;

Documentation: https://docs.rs/bl4

JavaScript/TypeScript

Browser:

import init, { SaveFile, decryptSav, encryptSav } from './pkg/bl4.js';

await init();

const encrypted = new Uint8Array(await file.arrayBuffer());
const yaml = decryptSav(encrypted, '76561197960521364');
const save = new SaveFile(yaml);

save.setCash(999999);
const modified = save.toYaml();
const encryptedNew = encryptSav(modified, '76561197960521364');

Node.js:

const { SaveFile, decryptSav, encryptSav } = require('./pkg/bl4.js');
const fs = require('fs');

const encrypted = fs.readFileSync('1.sav');
const yaml = decryptSav(encrypted, '76561197960521364');
const save = new SaveFile(yaml);

save.setCash(999999);
fs.writeFileSync('1.sav', encryptSav(save.toYaml(), '76561197960521364'));

TypeScript definitions included automatically.

Development

Tests

cargo test

WASM Build

cd crates/bl4
./build-wasm.sh

Generates bindings and TypeScript definitions in pkg/.

Save File Format

1. AES-256-ECB encryption (Steam ID-derived key via XOR with BASE_KEY)
2. Zlib compression
3. YAML data

.sav -> decrypt (AES-256-ECB) -> decompress (zlib) -> YAML

Contributing

Areas for contribution:

• Item serial decoding
• Save structure documentation
• GUI development
• Platform testing
• Additional convenience methods

Releases

1. Update versions in Cargo.toml files
2. Commit and tag: git tag v0.1.0 && git push origin v0.1.0
3. GitHub Actions handles publishing to crates.io, NPM, and binary releases

Disclaimer

This repository contains unofficial tools. Borderlands and all related trademarks are property of Gearbox Software and 2K. This project is not affiliated with or endorsed by Gearbox Software or 2K.

Use at your own risk.

License

BSD-2-Clause

lib.rs:

bl4

Borderlands 4 save editor library - encryption, decryption, and parsing.

This library provides functionality to:

• Decrypt and encrypt Borderlands 4 .sav files
• Parse decrypted YAML save data
• Decode item serials (weapons, equipment, etc.)
• Modify save data (level, currency, inventory, etc.)

Example

use std::fs;

let encrypted = fs::read("1.sav")?;
let steam_id = "76561197960521364";

// Decrypt and parse save file
let yaml_data = bl4::decrypt_sav(&encrypted, steam_id)?;
let mut save = bl4::SaveFile::from_yaml(&yaml_data)?;

// Query and modify save data
println!("Character: {:?}", save.get_character_name());
println!("Cash: {:?}", save.get_cash());

save.set_cash(999999)?;
save.set_character_name("NewName")?;

// Re-encrypt and save
let modified_yaml = save.to_yaml()?;
let encrypted = bl4::encrypt_sav(&modified_yaml, steam_id)?;
fs::write("1.sav", encrypted)?;