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Address Format#

X Layer is an EVM-compatible blockchain network that supports two address formats: Standard EVM Address Format and XKO Prefix Address Format.

Supported Address Formats#

Standard EVM Address Format#

Format: 0x + 40 hexadecimal characters
Example: 0x70586BeEB7b7Aa2e7966DF9c8493C6CbFd75C625
Features:
- Complies with EIP-55 checksum standard (mixed case)
- Fully compatible with all Ethereum tools and wallets

XKO Prefix Address Format#

Format: XKO + 40 hexadecimal characters
Example: XKO70586BeEB7b7Aa2e7966DF9c8493C6CbFd75C625
Features:
- X Layer proprietary address format
- Case-insensitive prefix (XKO, xko, Xko all valid)
- Preserves EIP-55 checksum casing
- Easy identification of X Layer ecosystem addresses

Address Equivalence#

The same account can be represented in both formats, pointing to the same on-chain account:

Standard EVM:  0x70586BeEB7b7Aa2e7966DF9c8493C6CbFd75C625
XKO address:   XKO70586BeEB7b7Aa2e7966DF9c8493C6CbFd75C625
               xko70586beeb7b7aa2e7966df9c8493c6cbfd75c625  ✓ Valid
               Xko70586beeb7b7aa2e7966df9c8493c6cbfd75c625  ✓ Valid

Invalid format examples:

XKO0x70586BeEB7b7Aa2e7966DF9c8493C6CbFd75C625  ✗ Cannot have both XKO and 0x

XKO Prefix Address Design#

XKO address is essentially an alternative representation of a standard EVM address:

Address Core: 40 hexadecimal characters (same as EVM address)
Prefix Replacement: XKO replaces 0x prefix
Checksum Preservation: Maintains Keccak-256 hash-based case checksum
On-Chain Storage: Stored as standard 20-byte address on-chain

SDK Integration Guide#

X Layer provides multi-language SDKs for address format conversion, supporting:

JavaScript
TypeScript
Python
Go
Rust
Java

Core APIs#

All SDKs provide two core functions:

Function	Purpose	Input	Output
`toEvmAddress`	Convert to standard EVM address	`0x...` / `XKO...` / bare address	`0x` + 40 chars (EIP-55 checksum)
`fromEvmAddress`	Convert to XKO address	`0x...` / bare address	`XKO` + 40 chars (preserves checksum)

Some SDKs also provide utility functions:

Function	Purpose	Available In
`isXlayerAddress`	Check if address is XKO format	Java

JavaScript SDK#

Installation:

npm install js-sha3

Usage Example:

const { toEvmAddress, fromEvmAddress } = require('./multiAddress.js');

// XKO to standard EVM address
const evmAddr = toEvmAddress('XKO70586beeb7b7aa2e7966df9c8493c6cbfd75c625');
console.log(evmAddr);
// Output: 0x70586BeEB7b7Aa2e7966DF9c8493C6CbFd75C625

// Standard EVM to XKO address
const xkoAddr = fromEvmAddress('0x70586BeEB7b7Aa2e7966DF9c8493C6CbFd75C625');
console.log(xkoAddr);
// Output: XKO70586BeEB7b7Aa2e7966DF9c8493C6CbFd75C625

// Supports multiple input formats
toEvmAddress('0x70586beeb7b7aa2e7966df9c8493c6cbfd75c625');  // ✓
toEvmAddress('70586beeb7b7aa2e7966df9c8493c6cbfd75c625');    // ✓
toEvmAddress('XKO70586beeb7b7aa2e7966df9c8493c6cbfd75c625'); // ✓

Error Handling:

try {
  toEvmAddress('invalid');
} catch (error) {
  console.error(error.message);
  // Output: Invalid address length: expected 40 hex chars, got 7
}

TypeScript SDK#

Installation:

npm install js-sha3

Usage Example:

import { toEvmAddress, fromEvmAddress } from './multiAddress';

// Type-safe address conversion
const evmAddr: string = toEvmAddress('XKO70586beeb7b7aa2e7966df9c8493c6cbfd75c625');
const xkoAddr: string = fromEvmAddress('0x70586BeEB7b7Aa2e7966DF9c8493C6CbFd75C625');

// Type checking
toEvmAddress(123); // TypeScript compile error

Python SDK#

Installation:

pip install eth-utils

Usage Example:

from multi_address import to_evm_address, from_evm_address

# XKO to EVM
evm_addr = to_evm_address('XKO70586beeb7b7aa2e7966df9c8493c6cbfd75c625')
print(evm_addr)
# Output: 0x70586BeEB7b7Aa2e7966DF9c8493C6CbFd75C625

# EVM to XKO
xko_addr = from_evm_address('0x70586BeEB7b7Aa2e7966DF9c8493C6CbFd75C625')
print(xko_addr)
# Output: XKO70586BeEB7b7Aa2e7966DF9c8493C6CbFd75C625

# Error handling
try:
    to_evm_address('invalid')
except ValueError as e:
    print(e)
    # Output: Invalid address length: expected 40 hex chars, got 7

Go SDK#

Installation:

go get golang.org/x/crypto/sha3

Usage Example:

package main

import (
    "fmt"
    "log"

    address "your-module/multi_address"
)

func main() {
    // XKO to EVM
    evmAddr, err := address.ToEvmAddress("XKO70586beeb7b7aa2e7966df9c8493c6cbfd75c625")
    if err != nil {
        log.Fatal(err)
    }
    fmt.Println(evmAddr)
    // Output: 0x70586BeEB7b7Aa2e7966DF9c8493C6CbFd75C625

    // EVM to XKO
    xkoAddr, err := address.FromEvmAddress("0x70586BeEB7b7Aa2e7966DF9c8493C6CbFd75C625")
    if err != nil {
        log.Fatal(err)
    }
    fmt.Println(xkoAddr)
    // Output: XKO70586BeEB7b7Aa2e7966DF9c8493C6CbFd75C625
}

Rust SDK#

Add Dependency (Cargo.toml):

[dependencies]
multi_address = { path = "path/to/address/rust" }

Usage Example:

use multi_address::{to_evm_address, from_evm_address};

fn main() {
    // XKO to EVM
    match to_evm_address("XKO70586beeb7b7aa2e7966df9c8493c6cbfd75c625") {
        Ok(evm_addr) => println!("{}", evm_addr),
        // Output: 0x70586BeEB7b7Aa2e7966DF9c8493C6CbFd75C625
        Err(e) => eprintln!("Error: {}", e),
    }

    // EVM to XKO
    match from_evm_address("0x70586BeEB7b7Aa2e7966DF9c8493C6CbFd75C625") {
        Ok(xko_addr) => println!("{}", xko_addr),
        // Output: XKO70586BeEB7b7Aa2e7966DF9c8493C6CbFd75C625
        Err(e) => eprintln!("Error: {}", e),
    }
}

Java SDK#

Maven Dependency:

<dependency>
  <groupId>com.okcoin</groupId>
  <artifactId>xlayer-sdk</artifactId>
  <version>0.2.1</version>
</dependency>

Usage Example:

import com.okcoin.MultiAddress;

public class Example {
    public static void main(String[] args) {
        // XKO to EVM
        String evmAddr = MultiAddress.toEvmAddress("XKO70586beeb7b7aa2e7966df9c8493c6cbfd75c625");
        System.out.println(evmAddr);
        // Output: 0x70586BeEB7b7Aa2e7966DF9c8493C6CbFd75C625

        // EVM to XKO
        String xkoAddr = MultiAddress.fromEvmAddress("0x70586BeEB7b7Aa2e7966DF9c8493C6CbFd75C625");
        System.out.println(xkoAddr);
        // Output: XKO70586BeEB7b7Aa2e7966DF9c8493C6CbFd75C625

        // Check if XKO address
        boolean isXko = MultiAddress.isXlayerAddress("XKO70586BeEB7b7Aa2e7966DF9c8493C6CbFd75C625");
        System.out.println(isXko); // true

        boolean isNotXko = MultiAddress.isXlayerAddress("0x70586BeEB7b7Aa2e7966DF9c8493C6CbFd75C625");
        System.out.println(isNotXko); // false

        // Error handling
        try {
            MultiAddress.toEvmAddress("invalid");
        } catch (IllegalArgumentException e) {
            System.err.println(e.getMessage());
            // Output: Invalid address length: expected 40 hex chars, got 7
        }
    }
}

Security Considerations#

Important: XKO addresses are only for off-chain interactions (UI display, etc.)

In transaction RLP encoding:

❌ Cannot use XKO format addresses
✅ Must use standard 20-byte address format
The chain automatically rejects transactions containing XKO format addresses

SDKs handle this conversion automatically, but if manually constructing transactions, use the standard format.

Frequently Asked Questions (FAQ)#

Q1: What's the difference between XKO and EVM addresses?#

A: They are completely equivalent on-chain, differing only in prefix. XKO addresses use XKO prefix, while EVM addresses use 0x prefix.

Q2: Can I use XKO addresses directly in transactions?#

A: No. When constructing RLP-encoded transactions, you must use the standard 20-byte address. XKO format is only for off-chain interactions (RPC queries, UI display).