In decentralized finance (DeFi), managing token permissions is a crucial step before executing trades, swaps, or interacting with smart contracts. One of the most common actions users and developers perform is checking a token’s approval allowance — essentially verifying how much a third-party address (like a DEX or trading protocol) is authorized to spend on behalf of a user.
While some platforms previously offered direct API endpoints to retrieve this data, OKX DEX has discontinued its built-in allowance query interface. As a result, developers and users must now rely on independent, blockchain-level methods to check token allowances effectively.
This guide walks you through a reliable, code-level approach to retrieve token approval limits on the Ethereum network using standard Web3 tools like web3.js. Whether you're building a wallet integration, trading bot, or DeFi dashboard, understanding this process is essential for secure and transparent user interactions.
Understanding Token Allowance in DeFi
Before diving into the technical implementation, let’s clarify what token allowance means in practice.
When you interact with decentralized exchanges (DEXs), lending protocols, or yield farms, you often need to "approve" a contract to access your tokens. This approval doesn’t transfer ownership — instead, it sets a spending limit for a specific address (the spender). The allowance is the amount the spender can withdraw from your wallet without further confirmation.
For example:
- You want to trade 10 USDT on a DEX.
- First, you approve the DEX’s router contract to spend up to 10 USDT from your balance.
- That approval creates an allowance entry in the token’s smart contract.
- Later, the DEX can pull funds up to that limit when you execute a trade.
👉 Learn how to securely manage your token approvals and track spending permissions across chains.
Why Manual Allowance Checks Are Necessary
Since OKX no longer provides a native API endpoint to query these allowances, developers must retrieve the data directly from the Ethereum blockchain. This ensures transparency and avoids dependency on intermediary services that may become outdated or unreliable.
By querying the blockchain directly:
- You get real-time, accurate allowance values.
- You maintain control over data sources.
- You reduce reliance on centralized APIs that could introduce latency or downtime.
The good news? This process is straightforward using widely adopted libraries such as web3.js.
Step-by-Step Guide: Querying Allowance on Ethereum
Here’s how to programmatically check a token’s approval allowance using JavaScript and web3.js.
1. Connect to an Ethereum Node
To interact with the blockchain, you need access to an Ethereum node. You can use:
- Public RPC endpoints (e.g., Infura, Alchemy, or Chainstack)
- Self-hosted nodes
- Free-tier services for development
const { Web3 } = require('web3');
// Replace with your actual node URL
const web3 = new Web3('https://mainnet.infura.io/v3/YOUR_INFURA_PROJECT_ID');Ensure your endpoint supports eth_call requests, which are required to read contract data.
2. Get the Token Contract Instance
Each ERC-20 token lives at a specific address and exposes functions via its ABI (Application Binary Interface). You’ll need:
- Token contract address (e.g., USDT:
0xdAC17F958D2ee523a2206206994597C13D831ec7) - Minimal ABI containing the
allowancefunction
const tokenAddress = '0xdAC17F958D2ee523a2206206994597C13D831ec7'; // Example: USDT
const tokenABI = [
{
constant: true,
inputs: [
{ name: '_owner', type: 'address' },
{ name: '_spender', type: 'address' }
],
name: 'allowance',
outputs: [{ name: '', type: 'uint256' }],
payable: false,
stateMutability: 'view',
type: 'function'
}
];
const tokenContract = new web3.eth.Contract(tokenABI, tokenAddress);You only need the allowance function in the ABI — no need to include full contract definitions unless required for other operations.
3. Query the Allowance
Now call the allowance(owner, spender) method to retrieve the current approved amount.
async function getAllowance(ownerAddress, spenderAddress) {
try {
const allowance = await tokenContract.methods.allowance(ownerAddress, spenderAddress).call();
console.log(`Allowance: ${web3.utils.fromWei(allowance, 'ether')} tokens`);
return allowance;
} catch (error) {
console.error('Failed to query allowance:', error);
}
}
// Example usage
const ownerAddress = '0xYourWalletAddress';
const spenderAddress = '0x40aa958dd87fc8305b97f2ba922cddca374bcd7f'; // OKX DEX approval address
getAllowance(ownerAddress, spenderAddress);💡 Tip: Use web3.utils.fromWei() to convert the returned value from wei to human-readable units (e.g., from 1e18 to 1 ETH or 1 USDT).4. Find the Correct Spender Address
The spender address is the contract authorized to spend your tokens. For OKX DEX integrations, refer to their official documentation for the correct dexTokenApproveAddress per chain.
👉 Access real-time contract addresses and integrate secure approval workflows in your dApp.
Core Keywords for SEO and Developer Search Intent
To ensure visibility among developers and Web3 builders searching for solutions, this guide naturally integrates key terms such as:
- token approval allowance
- check ERC-20 allowance
- web3.js allowance query
- DEX token authorization
- Ethereum smart contract interaction
- wallet approval tracking
- blockchain permission check
- API for token spending limit
These keywords align with high-intent searches related to DeFi security, smart contract debugging, and wallet integrations.
Frequently Asked Questions (FAQ)
Q: Why did OKX remove the allowance query API?
A: OKX has streamlined its DEX API offerings and now encourages developers to interact directly with blockchain data for greater accuracy and decentralization. This shift aligns with industry best practices for transparency and reliability.
Q: Can I use ethers.js instead of web3.js?
A: Yes. While this example uses web3.js, you can achieve the same result with ethers.js using similar logic. Both libraries support calling read-only methods like allowance() from ERC-20 contracts.
Q: Is querying allowance safe? Does it cost gas?
A: Yes, it's completely safe. The allowance() function is a view method — it reads data without modifying state and does not cost any gas. It’s executed locally via an eth_call.
Q: What if I get zero allowance even after approving?
A: Double-check:
- The correct token address
- The correct spender address
- The network (mainnet vs. testnet)
- Whether the transaction was confirmed
You can verify past approvals using block explorers like Etherscan.
Q: How can I revoke an existing allowance?
A: You can set the allowance back to zero by calling the approve(spender, 0) function on the token contract. This is recommended before re-approving large amounts for security.
Final Thoughts
Although OKX no longer offers a direct API for checking token allowances, the ability to query this data directly from the blockchain empowers developers with more control and resilience. By leveraging tools like web3.js, you can build robust, secure applications that help users manage their DeFi permissions transparently.
Whether you're monitoring trading limits, auditing wallet security, or integrating with decentralized protocols, understanding how to retrieve token approval allowances is a foundational skill in Web3 development.