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Quickstart
Sim is a real-time blockchain data API by Dune. It gives developers instant access to wallet balances, token metadata, transaction history, and onchain activity across 60+ EVM chains and Solana — all through a single API key, with no indexer setup required. With webhook subscriptions, you can also push data directly to your app in real time. This guide will help you make your first API call to retrieve multichain token balances for an address.

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Authentication

Sim APIs use API keys to authenticate requests. You can create and manage your API keys in your Sim Dashboard.
To authenticate, include your API key in the X-Sim-Api-Key header for every request. 
curl --request GET \
  --header "X-Sim-Api-Key: YOUR_API_KEY"
All API requests must be made over HTTPS. Calls made over plain HTTP will fail. API requests without authentication will also fail.
Your API keys carry many privileges, so be sure to keep them secure. Do not share your secret API keys in public places like GitHub, client-side code, and so on.

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Your First Request

Let’s make your first request. We’ll retrieve token balances for 0xd8da6bf26964af9d7eed9e03e53415d37aa96045 (Vitalik’s wallet) across multiple EVM chains using the Balances API. Here’s how to make the API call: 
curl -X GET "https://api.sim.dune.com/v1/evm/balances/0xd8da6bf26964af9d7eed9e03e53415d37aa96045" \
     -H "X-Sim-Api-Key: YOUR_API_KEY"
Replace YOUR_API_KEY with your actual API key from the Sim Dashboard.
The API will return a JSON response containing an array of balances. Each object in the array represents a token balance for the specified address on one of the chains, including various details.
Response (JSON)
{
  "balances": [
    {
      "address": "native",
      "amount": "605371497350928252303",
      "chain": "ethereum",
      "decimals": 18,
      "price_usd": 3042.816964922323,
      "symbol": "ETH",
      "value_usd": 1842034.6622198338
    }
  ],
  "next_offset": "dKMBWDLqM7vlyn5OMEXsLWp0nI4AAAABA5JLazNO7x4poVGqUwsgxgqvvIg",
  "request_time": "2023-11-07T05:31:56Z",
  "response_time": "2023-11-07T05:31:56Z",
  "wallet_address": "0xd8da6bf26964af9d7eed9e03e53415d37aa96045"
}
With a single API request you get normalized, realtime data with enriched metadata and pricing.

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Next Steps

After making your first API call to Sim APIs, you’ll either see the JSON response shown above (success!) or you might encounter an error. If you received an error, check out our Error Handling Guide for troubleshooting tips and best practices. If your call was successful, you’ve seen how easily you can retrieve comprehensive, multichain data. But this is just the beginning of what’s possible. Are you ready to learn more? Here are a few paths you can explore:

Get Real-Time Notifications

Set up webhook subscriptions to receive instant notifications for balance changes, activity, and transactions — no polling required.

Explore EVM Endpoints

Access balances, activity, transactions, NFTs, and more across 60+ Ethereum and EVM-compatible chains.

Explore Solana Endpoints

Get real-time balances and transactions on Solana and Eclipse.

Build Real App Features

Follow our practical guides to build fully-functional features like token portfolio displays, real-time activity feeds, and more for your onchain apps.

Build with AI

Speed up your development using Sim APIs with our LLM-friendly resources.