# Browser JavaScript | Sentry for JavaScript
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## [Prerequisites](https://docs.sentry.io/platforms/javascript.md#prerequisites)
You need:
* A Sentry [account](https://sentry.io/signup/) and [project](https://docs.sentry.io/product/projects.md)
* Your application up and running
## [Install](https://docs.sentry.io/platforms/javascript.md#install)
Sentry captures data by using an SDK within your application's runtime.
In order to get started using the Sentry JavaScript SDK, add the following code to the top of your application, before all other scripts:
```html
```
The Loader Script allows you to configure some SDK features from the Sentry UI, without having to redeploy your application. The [Loader Script documentation](https://docs.sentry.io/platforms/javascript/install/loader.md) shows more information about how to use it.
Alternatively, you can also install the SDK via a package manager:
```bash
npm install @sentry/browser --save
```
We also support installation via [CDN bundles](https://docs.sentry.io/platforms/javascript/install/loader.md#cdn).
If you're updating your Sentry SDK to the latest version, check out our [migration guide](https://github.com/getsentry/sentry-javascript/blob/master/MIGRATION.md) to learn more about breaking changes.
If you are using our previous Browser JavaScript SDK, you can access the [legacy SDK documentation](https://docs.sentry.io/platforms/javascript/legacy-sdk.md), until further notice.
## [Configure](https://docs.sentry.io/platforms/javascript.md#configure)
Configuration should happen as early as possible in your application's lifecycle.
Error Monitoring\[ ]Logs\[ ]Session Replay\[ ]Tracing\[ ]User Feedback
Once this is done, Sentry's JavaScript SDK will capture all unhandled exceptions, transactions, and Session Replays, based on the sample rates set.
Note, that configuration differs slightly depending on how you installed the Sentry SDK. Make sure to follow the instructions in the correct tab, depending on if you installed the Sentry SDK via NPM, using the Loader Script, or via CDN.
```javascript
import * as Sentry from "@sentry/browser";
Sentry.init({
dsn: "https://examplePublicKey@o0.ingest.sentry.io/0",
// Adds request headers and IP for users, for more info visit:
// https://docs.sentry.io/platforms/javascript/configuration/options/#sendDefaultPii
sendDefaultPii: true,
// Alternatively, use `process.env.npm_package_version` for a dynamic release version
// if your build tool supports it.
release: "my-project-name@2.3.12",
integrations: [
// performance
Sentry.browserTracingIntegration(),
// performance
// session-replay
Sentry.replayIntegration(),
// session-replay
// user-feedback
Sentry.feedbackIntegration({
// Additional SDK configuration goes in here, for example:
colorScheme: "system",
}),
// user-feedback
],
// logs
// Enable logs to be sent to Sentry
enableLogs: true,
// logs
// performance
// Set tracesSampleRate to 1.0 to capture 100%
// of transactions for tracing.
// We recommend adjusting this value in production
// Learn more at
// https://docs.sentry.io/platforms/javascript/configuration/options/#traces-sample-rate
tracesSampleRate: 1.0,
// Set `tracePropagationTargets` to control for which URLs trace propagation should be enabled
tracePropagationTargets: ["localhost", /^https:\/\/yourserver\.io\/api/],
// performance
// session-replay
// Capture Replay for 10% of all sessions,
// plus for 100% of sessions with an error
// Learn more at
// https://docs.sentry.io/platforms/javascript/session-replay/configuration/#general-integration-configuration
replaysSessionSampleRate: 0.1,
replaysOnErrorSampleRate: 1.0,
// session-replay
});
```
## [Add Readable Stack Traces to Errors](https://docs.sentry.io/platforms/javascript.md#add-readable-stack-traces-to-errors)
Depending on how you've set up your project, the stack traces in your Sentry errors probably won't look like your actual code.
To fix this, upload your source maps to Sentry. The easiest way to do this is by using the Sentry Wizard:
```bash
npx @sentry/wizard@latest -i sourcemaps
```
The wizard will guide you through the following steps:
* Logging into Sentry and selecting a project
* Installing the necessary Sentry packages
* Configuring your build tool to generate and upload source maps
* Configuring your CI to upload source maps
For more information on source maps or for more options to upload them, head over to our [Source Maps](https://docs.sentry.io/platforms/javascript/sourcemaps.md) documentation.
## [Verify](https://docs.sentry.io/platforms/javascript.md#verify)
This snippet includes an intentional error, so you can test that everything is working as soon as you set it up.
```javascript
setTimeout(() => {
throw new Error("Sentry Test Error");
});
```
Errors triggered from within Browser DevTools are sandboxed and won't trigger an error handler. Place the snippet directly in your code instead.
Learn more about manually capturing an error or message in our [Usage documentation](https://docs.sentry.io/platforms/javascript/usage.md).
To view and resolve the recorded error, log into [sentry.io](https://sentry.io) and select your project. Clicking on the error's title will open a page where you can see detailed information and mark it as resolved.