# Scopes | Sentry for React Native

When an event is captured and sent to Sentry, SDKs will merge that event data with extra information from the current scope. SDKs will typically automatically manage the scopes for you in the framework integrations and you don't need to think about them. However, you should know what a scope is and how you can use it to your advantage.

## [What's a Scope?](https://docs.sentry.io/.md#whats-a-scope)

Scopes hold useful information that gets sent along with the event. For instance, [contexts](https://docs.sentry.io/context.md) and [breadcrumbs](https://docs.sentry.io/breadcrumbs.md) are stored on the scope. When a scope is forked, it inherits all data from its parent scope.

The default SDK integrations will fork scopes intelligently. For instance, web framework integrations will fork scopes around your routes or request handlers.

## [How Scopes Work](https://docs.sentry.io/.md#how-scopes-work)

Scopes are basically stacks of data that are attached to events. When an event is captured, the SDK will merge the data from the active scopes into the event. This allows you to attach data to events that is relevant to the context in which the event was captured.

A scope is generally valid inside of a callback or an execution context. This means that multiple parts of your application may have different scopes active at the same time. For instance, a web server might handle multiple requests at the same time, and each request may have different scope data to apply to its events.

## [Different Kinds of Scopes](https://docs.sentry.io/.md#different-kinds-of-scopes)

The Sentry SDK has three different kinds of scopes:

* [Global scope](https://docs.sentry.io/.md#global-scope)
* [Isolation scope](https://docs.sentry.io/.md#isolation-scope)
* [Current scope](https://docs.sentry.io/.md#current-scope)

### [Global Scope](https://docs.sentry.io/.md#global-scope)

The global scope is applied to *all* events, no matter where they originate. You can use it to store data that should apply to all events, such as environmental information.

You can access the global scope via `Sentry.getGlobalScope()`.

Note, that the global scope can only be used to write data, not to capture events. Events can only be captured on the current scope (for example, `getCurrentScope().captureException()` and similar APIs).

### [Isolation Scope](https://docs.sentry.io/.md#isolation-scope)

The isolation scope is used to isolate events from each other. For example, each request in a web server might get its own isolation scope, so that events from one request don't interfere with events from another. In most cases, you'll want to put data that should be applied to your events on the isolation scope. This is why all `Sentry.setXXX` methods, like `Sentry.setTag()` will write data onto the currently active isolation scope. A classic example of data that belongs on the isolation scope is user data, where each request may have a different user, so you'd want to make sure that the user is set on the isolation scope.

You can access the isolation scope via `Sentry.getIsolationScope()`, but usually you'll just use the `Sentry.setXXX` methods to set data on the currently active isolation scope:

```javascript
Sentry.setTag("my-tag", "my value");
// Is identical to:
Sentry.getIsolationScope().setTag("my-tag", "my value");
```

Note, that the isolation scope can only be used to write data, not to capture events. Events can only be captured on the current scope (for example, `getCurrentScope().captureException()` and similar APIs).

### [Current Scope](https://docs.sentry.io/.md#current-scope)

Current scope is the local scope that's currently active. Unlike the rarely-forked isolation scope, the current scope may be forked more frequently and under the hood. It can be used to store data that should only be applied to specific events. In most cases, you shouldn't access this scope directly, but use `Sentry.withScope` to create a new scope that's only active for a specific part of your code:

```javascript
Sentry.withScope((scope) => {
  // scope is the current scope inside of this callback!
  scope.setTag("my-tag", "my value");
  // this tag will only be applied to events captured inside of this callback
  // the following event will have the tag:
  Sentry.captureException(new Error("my error"));
});
// this event will not have the tag:
Sentry.captureException(new Error("my other error"));
```

You can access the current scope via `Sentry.getCurrentScope()`, but you should use `Sentry.withScope()` to interact with local scopes in most cases instead.

## [How Scope Data is Applied to Events](https://docs.sentry.io/.md#how-scope-data-is-applied-to-events)

Before an event (like an error or transaction) is sent to Sentry, the currently active scopes are applied to it.

The global scope is applied first, followed by the isolation scope, and finally the current scope. This means that any data set on the current scope will take precedence over data set on the isolation and global scopes:

```javascript
Sentry.getGlobalScope().setExtras({
  shared: "global",
  global: "data",
});
Sentry.getIsolationScope().setExtras({
  shared: "isolation",
  isolation: "data",
});
Sentry.getCurrentScope().setExtras({
  shared: "current",
  current: "data",
});

Sentry.captureException(new Error("my error"));
// --> Will have the following extra:
// { shared: 'current', global: 'data', isolation: 'data', current: 'data' }
```

## [Configuring the Scope](https://docs.sentry.io/.md#configuring-the-scope)

There are two main ways to interact with the scope. You can access the current scope via `Sentry.getCurrentScope()` and use setters on the resulting scope, or you can use global methods like `Sentry.setTag()` directly, which will set on the respective scope under the hood (this will be the isolation scope).

You'll first need to import the SDK, as usual:

```javascript
import * as Sentry from "@sentry/browser";
```

You can, for instance, add custom tags or inform Sentry about the currently authenticated user.

```javascript
/// Usually, you don't want to write on the current scope, so use with care!
const scope = Sentry.getCurrentScope();
scope.setTag("my-tag", "my value");
scope.setUser({
  id: 42,
  email: "john.doe@example.com",
});

// Or use the global methods (which will set data on the isolation scope):
Sentry.setTag("my-tag", "my value");
Sentry.setUser({
  id: 42,
  email: "john.doe@example.com",
});
```

To learn what useful information can be associated with scopes see [context](https://docs.sentry.io/context.md), [tags](https://docs.sentry.io/tags.md), [users](https://docs.sentry.io/identify-user.md) and [breadcrumbs](https://docs.sentry.io/breadcrumbs.md).

## [Using `withScope`](https://docs.sentry.io/.md#using-withscope)

In the following example we use `withScope` to attach a `level` and a `tag` to only one specific error:

```javascript
Sentry.withScope(function (scope) {
  scope.setTag("my-tag", "my value");
  scope.setLevel("warning");
  // will be tagged with my-tag="my value"
  Sentry.captureException(new Error("my error"));
});

// will not be tagged with my-tag
Sentry.captureException(new Error("my other error"));
```

The scope inside the `withScope()` callback is only valid inside of the callback. Once the callback ends, the scope will be removed and will no longer apply. The inner scope is only applied to events that are captured inside of the callback. `withScope()` will clone (or fork) the current scope, so the current scope won't be modified. This allows you to more easily isolate pieces of context information to specific locations in your code or even call `clear` to briefly remove all context information.
