# Authentication

The Market Data API uses a **Bearer Token** for authentication. The token is required for almost every request. Your token should have been e-mailed to you when you first signed up for an account. If you do not have a token or have lost your sign-up email, request a new token from the [Market Data Dashboard](https://www.marketdata.app/dashboard/).

There are three ways to set your token when using the Java SDK:

1. Set it from an environment variable _(recommended for production)_
2. Load it from a `.env` file _(recommended for local development)_
3. Pass it directly when creating the [client](https://www.marketdata.app/docs/sdk/java/client)

On startup, the SDK looks for the `MARKETDATA_TOKEN` environment variable. If found, it uses that token for all requests. The SDK also loads a `.env` file automatically from the working directory if one is present.

> [!TIP]
> When your code is running in a production environment, we recommend using an environment variable to ensure your token is not stored with your code. This is the most secure way to set your token.

## How To Set Up The Environment Variable

### Set The Environment Variable In The Console

### Mac / Linux

This command sets the environment variable for the current session only. If you open a new terminal or restart your computer, it will not persist.

```bash
export MARKETDATA_TOKEN="your_api_token"
```

#### Make The Variable Persistent

Add the `export` line to your shell's profile script (`~/.zshrc`, `~/.bashrc`, `~/.bash_profile`, etc.), then restart your terminal or run `source ~/.zshrc` (adjusting for your shell).

### Windows

`setx` sets the variable permanently, but it is not available in the current Command Prompt session — open a new one after running it.

```bash
setx MARKETDATA_TOKEN "your_api_token"
```

### Using a .env File

The SDK automatically loads a `.env` file from your working directory at startup. Create a file named `.env` in your project root:

```env title=".env"
MARKETDATA_TOKEN=your_api_token
```

> [!WARNING]
> Add `.env` to your `.gitignore` so the token is not committed to source control.

### Make A Test Request

Verify your authentication is working by making a test request against `SPY` (or any symbol that requires authentication). Do **not** use `AAPL` to test authentication — `AAPL` is a free test symbol and returns data even when you are not authenticated.

### Java

```java
import com.marketdata.sdk.MarketDataClient;
import com.marketdata.sdk.stocks.StockQuoteRequest;
import com.marketdata.sdk.exception.AuthenticationError;

// No need to pass a token here — the SDK reads MARKETDATA_TOKEN automatically.
try (MarketDataClient client = new MarketDataClient()) {
  var quote = client.stocks().quote(StockQuoteRequest.of("SPY")).values().get(0);
  System.out.println(quote.symbol() + " last=" + quote.last());
} catch (AuthenticationError e) {
  System.out.println("Authentication failed: " + e.getMessage());
}
```

### Kotlin

```kotlin
import com.marketdata.sdk.MarketDataClient
import com.marketdata.sdk.stocks.StockQuoteRequest
import com.marketdata.sdk.exception.AuthenticationError

MarketDataClient().use { client ->
    try {
        val quote = client.stocks().quote(StockQuoteRequest.of("SPY")).values()[0]
        println("${quote.symbol()} last=${quote.last()}")
    } catch (e: AuthenticationError) {
        println("Authentication failed: ${e.message}")
    }
}
```

## Passing the Token Directly

If you prefer to pass the token explicitly (not recommended for production code), use the four-argument constructor `(apiKey, baseUrl, apiVersion, validateOnStartup)`. Pass `null` for any slot you want resolved from the cascade or left at its default.

### Java

```java
import com.marketdata.sdk.MarketDataClient;

try (MarketDataClient client =
         new MarketDataClient("your_token_here", null, null, true)) {
  // ... make requests
}
```

### Kotlin

```kotlin
import com.marketdata.sdk.MarketDataClient

MarketDataClient("your_token_here", null, null, true).use { client ->
    // ... make requests
}
```

> [!NOTE]
> **Demo mode**
>
> If no token is found anywhere in the cascade, the SDK runs in **demo mode** — startup validation is skipped and you can call the free, public endpoints (such as `AAPL` quotes and `utilities().status()`).

## Next Steps

After successful authentication, read the overview of how the [client](https://www.marketdata.app/docs/sdk/java/client) works, then configure [Settings](https://www.marketdata.app/docs/sdk/java/settings) to customize output format, date format, and other universal parameters.