# Overview

The Decentraland scene runtime is the sandboxed execution environment where a [scene](https://github.com/decentraland/docs/blob/main/content/entity-types/scenes.md) runs its main script.

Each scene runs inside its own isolated runtime. Within it, it has access to certain [global objects](https://github.com/decentraland/docs/blob/main/contributor/globals.md) and can import [modules](https://github.com/decentraland/docs/blob/main/contributor/modules.md) from the runtime library.

{% @mermaid/diagram content="flowchart TB
subgraph WorldExplorer\["World Explorer"]
subgraph Runtime1\["Runtime 1"]
Scene1\["Scene"]
end

```
    subgraph Runtime2["Runtime 2"]
        Scene2["Scene"]
    end
    
    subgraph Runtime3["Runtime 3"]
        Scene3["Scene"]
    end
    
    Scene1 --> Library["Runtime Module Library"]
    Scene2 --> Library
    Scene3 --> Library
end" %}
```

By importing modules from the runtime library, scenes have access a wide array of functionality, including:

* Create entities and control their behavior
* Interact with the player
* Communicate with other players
* Inspect the state of the world
* Connect to external services
* Make web3 payments

In practice, scenes bundle the [Decentraland SDK](https://github.com/decentraland/docs/blob/main/contributor/creator/sdk7/getting-started/sdk-101.md) with their code, which encapsulates the RPC-style interface of the runtime library and provides a nicer and more comfortable API.

{% hint style="info" %}
Note that the SDK is *not* part of the Decentraland protocol, only the lower-level interfaces are. Scenes can decide whether to bundle the SDK or use alternative libraries.
{% endhint %}

### Global Objects

Inside the sandboxed environment, [scenes](https://github.com/decentraland/docs/blob/main/content/entity-types/scenes.md) assume certain objects and functions are globally available. Some are standard ES2020 objects (like `Date` or `Math`), and others are injected by the runtime to implement functionality such as requiring modules, logging messages and scheduling callbacks.

Se [globals](https://github.com/decentraland/docs/blob/main/contributor/globals.md) for more details.

### Modules

The [`require`](https://github.com/decentraland/docs/blob/main/contributor/globals.md#module) global function can import modules provided by the [runtime library](https://github.com/decentraland/docs/blob/main/contributor/execution.md). These modules allow selectively importing utilities such as the ECS or Communications systems.

See the runtime modules section for a comprehensive list.

### Execution

The runtime requires that scenes implement a specific set of methods, and guarantees they will be called according to certain rules.

See [execution](https://github.com/decentraland/docs/blob/main/contributor/execution.md) for more on this.

### Permissions

Sensitive functionality, such as making HTTP requests to 3rd party services, is restricted by the runtime unless certain permissions are requested by the [scene](https://github.com/decentraland/docs/blob/main/content/entity-types/scenes.md), and granted by the player.

See [permissions](https://github.com/decentraland/docs/blob/main/contributor/permissions.md) to learn more.