> ## Documentation Index
> Fetch the complete documentation index at: https://docs.getpara.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Manage Token Allowances

> Approve tokens, check allowances, and implement permit signatures

export const Link = ({href, label, newTab = false}) => {
  const [isHovered, setIsHovered] = useState(false);
  return <a href={href} target={newTab ? '_blank' : '_self'} rel={newTab ? 'noopener noreferrer' : undefined} className="not-prose inline-block relative text-black font-semibold cursor-pointer border-b-0 no-underline" onMouseEnter={() => setIsHovered(true)} onMouseLeave={() => setIsHovered(false)}>
      {label}
      <span className={`absolute left-0 bottom-0 w-full rounded-sm bg-gradient-to-r from-orange-600 to-purple-600 transition-all duration-300 ${isHovered ? 'h-0.5' : 'h-px'}`} />
    </a>;
};

export const Card = ({imgUrl, title, description, href, horizontal = false, newTab = false}) => {
  const [isHovered, setIsHovered] = useState(false);
  const handleClick = e => {
    e.preventDefault();
    if (newTab) {
      window.open(href, '_blank', 'noopener,noreferrer');
    } else {
      window.location.href = href;
    }
  };
  return <div className={`not-prose relative my-2 p-[1px] rounded-xl transition-all duration-300 ${isHovered ? 'bg-gradient-to-r from-[#FF4E00] to-[#874AE3]' : 'bg-gray-200'}`} onMouseEnter={() => setIsHovered(true)} onMouseLeave={() => setIsHovered(false)}>
      <a href={href} onClick={handleClick} className={`not-prose flex ${horizontal ? 'flex-row' : 'flex-col'} font-normal h-full bg-white overflow-hidden w-full cursor-pointer rounded-[11px] no-underline`}>
        {imgUrl && <div className={`relative overflow-hidden flex-shrink-0 ${horizontal ? 'w-[30%] rounded-l-[11px]' : 'w-full'}`} onClick={e => e.stopPropagation()}>
            <img src={imgUrl} alt={title} className="w-full h-full object-cover pointer-events-none select-none" draggable="false" />
            <div className="absolute inset-0 pointer-events-none" />
          </div>}
        <div className={`flex-grow px-6 py-5 ${horizontal ? 'w-[70%]' : 'w-full'} flex flex-col ${horizontal && imgUrl ? 'justify-center' : 'justify-start'}`}>
          {title && <h2 className="font-semibold text-base text-gray-800 m-0">{title}</h2>}
          {description && <div className={`font-normal text-gray-500 re leading-6 ${horizontal || !imgUrl ? 'mt-0' : 'mt-1'}`}>
              <p className="m-0 text-xs">{description}</p>
            </div>}
        </div>
      </a>
    </div>;
};

Manage ERC-20 token allowances to allow smart contracts to spend tokens on behalf of a user. This guide covers checking and setting allowances using <Link label="Ethers.js" href="https://docs.ethers.org/v6/api/contract/contract/#Contract-approve" />, <Link label="Viem" href="https://viem.sh/docs/contract/writeContract.html" />, and <Link label="Wagmi" href="https://wagmi.sh/react/hooks/useWriteContract" />.

## Prerequisites

You need Web3 libraries configured with Para authentication.

<Card title="Setup Web3 Libraries" description="Configure Ethers.js, Viem, or Wagmi with Para before proceeding" href="/v2/react/guides/web3-operations/evm/setup-libraries" />

## Manage Token Allowances

<Tabs>
  <Tab title="Ethers.js">
    ```typescript theme={null}
    import { ethers } from "ethers";

    const ERC20_ABI = [
      "function allowance(address owner, address spender) view returns (uint256)",
      "function approve(address spender, uint256 amount) returns (bool)",
    ];

    async function checkAllowance(
      provider: ethers.Provider,
      tokenAddress: string,
      owner: string,
      spender: string
    ) {
      const contract = new ethers.Contract(tokenAddress, ERC20_ABI, provider);
      const allowance = await contract.allowance(owner, spender);
      return allowance;
    }

    async function approveToken(
      signer: ethers.Signer,
      tokenAddress: string,
      spender: string,
      amount: string
    ) {
      const contract = new ethers.Contract(tokenAddress, ERC20_ABI, signer);
      const tx = await contract.approve(spender, ethers.parseEther(amount));
      await tx.wait();
      return tx;
    }
    ```
  </Tab>

  <Tab title="Viem">
    ```tsx theme={null}
    import { useParaViemClient, useParaViemWriteContract } from "@getpara/react-sdk";
    import { parseEther, http } from "viem";
    import { sepolia } from "viem/chains";

    const ERC20_ABI = [
      {
        name: "approve",
        type: "function",
        stateMutability: "nonpayable",
        inputs: [
          { name: "spender", type: "address" },
          { name: "amount", type: "uint256" },
        ],
        outputs: [{ type: "bool" }],
      },
    ] as const;

    function TokenAllowance({
      tokenAddress,
      spender,
    }: {
      tokenAddress: `0x${string}`;
      spender: `0x${string}`;
    }) {
      const { viemClient } = useParaViemClient({
        walletClientConfig: { chain: sepolia, transport: http() },
      });

      const {
        writeContractAsync,
        isPending,
        data: hash,
      } = useParaViemWriteContract(viemClient);

      return (
        <div>
          <button
            disabled={isPending}
            onClick={() =>
              writeContract({
                address: tokenAddress,
                abi: ERC20_ABI,
                functionName: "approve",
                args: [spender, parseEther("100")],
              })
            }
          >
            {isPending ? "Approving..." : "Approve 100 Tokens"}
          </button>
          {hash && <p>Transaction: {hash}</p>}
        </div>
      );
    }
    ```
  </Tab>

  <Tab title="Wagmi">
    ```typescript theme={null}
    import { useReadContract, useWriteContract } from "@getpara/react-sdk/wagmi";
    import { parseEther } from "viem";

    const ERC20_ABI = [
      {
        name: "allowance",
        type: "function",
        stateMutability: "view",
        inputs: [
          { name: "owner", type: "address" },
          { name: "spender", type: "address" },
        ],
        outputs: [{ type: "uint256" }],
      },
      {
        name: "approve",
        type: "function",
        stateMutability: "nonpayable",
        inputs: [
          { name: "spender", type: "address" },
          { name: "amount", type: "uint256" },
        ],
        outputs: [{ type: "bool" }],
      },
    ] as const;

    function TokenAllowance(
      tokenAddress: `0x${string}`,
      owner: `0x${string}`,
      spender: `0x${string}`
    ) {
      const { data: allowance } = useReadContract({
        address: tokenAddress,
        abi: ERC20_ABI,
        functionName: "allowance",
        args: [owner, spender],
      });

      const { writeContract } = useWriteContract();

      return (
        <div>
          <p>Allowance: {allowance?.toString()}</p>
          <button
            onClick={() =>
              writeContract({
                address: tokenAddress,
                abi: ERC20_ABI,
                functionName: "approve",
                args: [spender, parseEther("100")],
              })
            }
          >
            Approve 100 Tokens
          </button>
        </div>
      );
    }
    ```
  </Tab>
</Tabs>