Quickstart
Sim APIs power wallets and onchain apps with fast, reliable access to real-time blockchain activity and ownership data. Access data from 60+ chains with a single request. 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 generate a new API key, visit the Keys page and click the New button.

Select Sim API for the key’s purpose when creating your new API key. 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:

Explore EVM Endpoints

See all available EVM API endpoints. Learn how to fetch transaction histories, token metadata, and more detailed onchain activity.

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.