Asset Changes - Explained

The beauty of simulation is that we can use any from address!

Let's simulate a transaction using the Asset Changes API and explain the results.

We will swap 1 USDC for UNI using Uniswap V2 as our example.

curl --location --request POST 'https://eth-mainnet.g.alchemy.com/v2/YOUR_KEY' \
--header 'Content-Type: application/json' \
--data-raw '{
   "jsonrpc": "2.0",
   "method": "alchemy_simulateAssetChanges",
   "id": 1,
   "params": [
      {
          "from": "0x07Eee3bfdfA311f6f06D419C8cCcA08a6EfDD162",
          "to": "0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D",
          "value": "0x0",
          "data": "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"
      }
   ]
}'

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": {
    "changes": [
      {
        "assetType": "ERC20",
        "changeType": "TRANSFER",
        "from": "0x07eee3bfdfa311f6f06d419c8ccca08a6efdd162",
        "to": "0xebfb684dd2b01e698ca6c14f10e4f289934a54d6",
        "rawAmount": "1000000",
        "contractAddress": "0xa0b86991c6218b36c1d19d4a2e9eb0ce3606eb48",
        "tokenId": null,
        "decimals": 6,
        "symbol": "USDC",
        "name": "USD Coin",
        "logo": "https://alchemyapi-res.cloudinary.com/image/upload/v1764179958/docs/api-reference/alchemy-transact/transaction-simulation/3408.png",
        "amount": "1"
      },
      {
        "assetType": "ERC20",
        "changeType": "TRANSFER",
        "from": "0xebfb684dd2b01e698ca6c14f10e4f289934a54d6",
        "to": "0x07eee3bfdfa311f6f06d419c8ccca08a6efdd162",
        "rawAmount": "186275962091465171",
        "contractAddress": "0x1f9840a85d5af5bf1d1762f925bdaddc4201f984",
        "tokenId": null,
        "decimals": 18,
        "symbol": "UNI",
        "name": "Uniswap",
        "logo": "https://alchemyapi-res.cloudinary.com/image/upload/v1764180255/docs/tutorials/transactions/transaction-simulation/7083.png",
        "amount": "0.186275962091465171"
      }
    ],
    "error": null
  }
}

User address - 0x07eee3bfdfa311f6f06d419c8ccca08a6efdd162 USDC contract - 0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48 USDC / UNI pool - 0xEBFb684dD2b01E698ca6c14F10e4f289934a54D6 Uniswap RouterV2 - 0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D UNI contract - 0x1f9840a85d5af5bf1d1762f925bdaddc4201f984

User (from) sends 1 USDC (contractAddress) to the Uniswap USDC / UNI pool (to).

{
  "assetType": "ERC20",
  "changeType": "TRANSFER",
  "from": "0x07eee3bfdfa311f6f06d419c8ccca08a6efdd162",
  "to": "0xebfb684dd2b01e698ca6c14f10e4f289934a54d6",
  "contractAddress": "0xa0b86991c6218b36c1d19d4a2e9eb0ce3606eb48",
  "symbol": "USDC",
  "amount": "1"
	...
},

The USDC / UNI pool (from) sends 0.186 UNI (contractAddress) to the user (to).

{
  "assetType": "ERC20",
  "changeType": "TRANSFER",
  "from": "0xebfb684dd2b01e698ca6c14f10e4f289934a54d6",
  "to": "0x07eee3bfdfa311f6f06d419c8ccca08a6efdd162",
  "contractAddress": "0x1f9840a85d5af5bf1d1762f925bdaddc4201f984",
  "symbol": "UNI",
  "amount": "0.186275962091465171"
	...
}

1 USDC was swapped for 0.186 UNI 🎉