Amplitude offers multiple ways to install browser SDKs, each with different product support and version control options. This guide compares the three main installation methods.

{% callout type="tip" %}
To skip manual setup, use the [Amplitude Wizard CLI](/docs/get-started/setup-wizard-cli). It reads your codebase, proposes tracking events, and instruments the SDK automatically with your approval.
{% /callout %}

## Choose your installation method

Amplitude provides three ways to install browser SDKs:

| Method                                      | Description                                         | Version control             | Best for                                                         |
| ------------------------------------------- | --------------------------------------------------- | --------------------------- | ---------------------------------------------------------------- |
| [Unified SDK (npm)](#unified-sdk-npm)       | Single npm package with all Amplitude features      | Customer-managed            | Teams requiring reproducible builds and strict change management |
| [Unified Script (CDN)](#unified-script-cdn) | Single script tag that loads Amplitude capabilities | Amplitude-managed           | Quick setup with automatic updates and sensible defaults         |
| [GTM Template](#google-tag-manager)         | Google Tag Manager template                         | Template version-controlled | Teams using GTM for tag management                               |

### Product support by installation method

Each installation method supports a different set of Amplitude products:

| Product                                                | Unified Script (CDN) | Unified SDK (npm) | GTM Template           |
| ------------------------------------------------------ | -------------------- | ----------------- | ---------------------- |
| Analytics (`@amplitude/analytics-browser`)             | ✅ Included          | ✅ Included       | ✅ Included            |
| Session Replay                                         | ✅ Included          | ✅ Included       | ✅ Optional (checkbox) |
| Guides & Surveys                                       | ⚠️ Separate script   | ✅ Included       | ✅ Optional (checkbox) |
| Web Experiment (`@amplitude/experiment-tag`)           | ✅ Included          | ❌ Not included   | ❌ Not supported       |
| Feature Experiment (`@amplitude/experiment-js-client`) | ❌ Not included      | ✅ Included       | ❌ Not supported       |

{% callout type="note" heading="Web Experiment compared with Feature Experiment" %}

- **Web Experiment**: uses visual editing for no-code A/B testing on web pages. The Unified Script includes it automatically.
- **Feature Experiment**: uses code-based feature flags with the Experiment JavaScript SDK. The Unified npm package includes it.
{% /callout %}

## Unified SDK (npm)

The Unified SDK provides a single npm package (`@amplitude/unified`) that gives you access to Analytics, Session Replay, Feature Experiment, and Guides & Surveys through a single API. Install it with npm or yarn, and control the version in your `package.json`.

**Key characteristics:**

- Customer-managed package installation with full control over versions.
- Includes Feature Experiment (code-based feature flags), not Web Experiment (visual editor).
- To upgrade, bump the package version in your dependency file.
- Best for teams that require reproducible builds and strict change management.

{% callout type="info" heading="Individual product installation" %}
If you're concerned about bundle size and only need specific products, install them individually:

- [Analytics](/docs/sdks/analytics/browser/browser-sdk-2): for tracking user events and behavior.
- [Experiment](/docs/sdks/experiment-sdks/experiment-javascript): for running A/B tests and feature flags.
- [Session Replay](/docs/session-replay/session-replay-standalone-sdk): for capturing and replaying user sessions.
- [Guides and Surveys](/docs/guides-and-surveys/sdk): for in-product messaging and surveys.
{% /callout %}

### Install the Unified SDK

Install the dependency with npm or yarn.

{% tabs tabs="npm, yarn, AI prompt" %}
{% tab name="npm" %}

```bash
npm install @amplitude/unified
```

{% /tab %}
{% tab name="yarn" %}

```bash
yarn add @amplitude/unified
```

{% /tab %}
{% tab name="AI prompt" %}
Use the getting started prompt generator to create an installation prompt with your Amplitude API key and selected setup options.

{% get-data-flowing /%}
{% /tab %}
{% /tabs %}

### Initialize the Unified SDK

The Unified SDK provides a single initialization method that initializes all Amplitude features.

```typescript
import { initAll } from "@amplitude/unified";

initAll("AMPLITUDE_API_KEY");
```

### Access SDK features

The Unified SDK provides access to all Amplitude features through a single interface:

{% callout type="info" heading="Feature documentation" %}
For details about each product's features and APIs, refer to its documentation:

- [Analytics Browser SDK](/docs/sdks/analytics/browser/browser-sdk-2).
- [Experiment JavaScript SDK](/docs/sdks/experiment-sdks/experiment-javascript).
- [Session Replay Standalone SDK](/docs/session-replay/session-replay-standalone-sdk).
- [Guides and Surveys Web SDK](/docs/guides-and-surveys/sdk).
{% /callout %}

```typescript
import { track, identify, experiment, sessionReplay } from "@amplitude/unified";

// Track events
track("Button Clicked", { buttonName: "Sign Up" });

// Identify users
identify(new Identify().set("userType", "premium"));

// Access Experiment features
const variant = await experiment.fetch("experiment-key");

// Access Session Replay features
sessionReplay.flush();
```

### Configuration

The Unified SDK supports configuration options for all Amplitude features. Configure each product individually while sharing some common options.

```typescript
import { initAll } from "@amplitude/unified";

initAll("AMPLITUDE_API_KEY", {
  // Shared options for all SDKs (optional)
  serverZone: "US", // or 'EU'
  instanceName: "my-instance",

  // Analytics options
  analytics: {
    // Analytics configuration options
  },

  // Session Replay options
  sessionReplay: {
    // Session Replay configuration options
    sampleRate: 1, // To enable session replay
  },

  // Experiment options
  experiment: {
    // Experiment configuration options
  },

  // Guides and Surveys options
  engagement: {
    // Guides and Surveys configuration options
  },
});
```

#### Shared options

| Name           | Type             | Default             | Description                                 |
| -------------- | ---------------- | ------------------- | ------------------------------------------- |
| `serverZone`   | `'US'` or `'EU'` | `'US'`              | The server zone to use for all SDKs.        |
| `instanceName` | `string`         | `$default_instance` | A unique name for this instance of the SDK. |

#### Analytics options

The Unified Browser SDK supports all options from `@amplitude/analytics-browser`. Refer to the [Analytics Browser SDK documentation](/docs/sdks/analytics/browser/browser-sdk-2#initialize-the-sdk) for details.

#### Session Replay options

The Unified Browser SDK supports all options from `@amplitude/plugin-session-replay-browser`. Refer to the [Session Replay Plugin documentation](/docs/sdks/session-replay/session-replay-plugin#configuration) for more information. To enable Session Replay, set `config.sessionReplay.sampleRate` to a non-zero value.

Sample rate controls the rate at which Amplitude captures session replays. For example, if you set `config.sessionReplay.sampleRate` to `0.5`, Session Replay captures roughly half of all sessions.

#### Experiment options

The Unified Browser SDK supports all options from `@amplitude/plugin-experiment-browser`. Refer to the [Experiment documentation](/docs/sdks/experiment-sdks/experiment-javascript#configuration) for details.

#### Guides and Surveys options

The Unified Browser SDK supports all [Guides and Surveys options](/docs/sdks/guides-and-surveys/sdk#initialize-the-sdk). The engagement plugin initializes by default.

##### Opting out of Guides & Surveys initialization

Guides & Surveys initializes by default in `@amplitude/unified`. If you don't use Guides & Surveys and want to prevent the engagement SDK from loading, pass `skip: true` in the `engagement` block. This prevents `amplitude.engagement.*` localStorage entries on properties that don't use Guides & Surveys.

**Requirements:** Requires `@amplitude/engagement-browser` 1.0.10 or later.

```typescript
initAll("AMPLITUDE_API_KEY", {
  // ... other options
  engagement: {
    skip: true,
  },
});
```

When `skip: true`, the engagement plugin returns immediately without setting up storage, network, or any Guides & Surveys-related side effects.

To enable Guides & Surveys later, remove the `skip: true` option (or set it to `false`) and re-initialize.

## Unified script (CDN)

The Unified Script is a single script tag that loads Amplitude browser capabilities from Amplitude's CDN. Amplitude controls the versions of the underlying SDKs remotely, offering a "single line of code" experience with sensible defaults and optional remote or manual configuration.

**Key characteristics:**

- Amplitude manages SDK versions and can patch bugs or improve performance centrally without requiring a customer release.
- Includes Web Experiment (visual editor) by default.
- Session Replay and Web Experiment enable automatically with default settings.
- Guides & Surveys requires a separate script because of size concerns.

### Install the Unified Script

Add the following script tag to the `<head>` of your site:

```html
<script src="https://cdn.amplitude.com/script/AMPLITUDE_API_KEY.js"></script>
```

Replace `AMPLITUDE_API_KEY` with your project's API key.

### Initialize the Unified Script

The Unified Script enables Session Replay and Web Experiment by default. For manual configuration:

```html
<script src="https://cdn.amplitude.com/script/AMPLITUDE_API_KEY.js"></script>
<script>
  window.amplitude.init("AMPLITUDE_API_KEY", {
    defaultTracking: true,
    autocapture: true,
    fetchRemoteConfig: true,
  });
  // Enable Session Replay with custom sample rate
  window.amplitude.add(window.sessionReplay.plugin({ sampleRate: 1 }));
</script>
```

### Add Guides & Surveys to the Unified Script

Because of size concerns, Guides & Surveys requires a separate script. Add it after the Unified Script:

```html
<script src="https://cdn.amplitude.com/script/AMPLITUDE_API_KEY.js"></script>
<script src="https://cdn.amplitude.com/script/AMPLITUDE_API_KEY.engagement.js"></script>
<script>
  window.amplitude.add(window.engagement.plugin());
  window.amplitude.init("AMPLITUDE_API_KEY", {
    fetchRemoteConfig: true,
    autocapture: true,
  });
</script>
```

Refer to the [Guides and Surveys SDK documentation](/docs/guides-and-surveys/sdk) for more configuration options.

## Google Tag Manager

The [Amplitude GTM template](/docs/data/source-catalog/google-tag-manager) directly wraps the Analytics Browser 2.0 SDK (`@amplitude/analytics-browser`). It doesn't use the Unified SDK or Unified Script.

**Key characteristics:**

- Template version-controlled through GTM.
- Supports Analytics, Session Replay, and Guides & Surveys.
- Doesn't support Web Experiment or Feature Experiment.
- Session Replay and Guides & Surveys default to disabled and require manual checkbox selection.

### Enable Session Replay and Guides & Surveys in GTM

To enable these features:

1. Go to your Amplitude tag in GTM.
2. In the tag configuration, select the **Session Replay** checkbox to enable session replays.
3. Select the **Guides & Surveys** checkbox to enable in-product messaging.
4. Save and publish your changes.

Refer to the [Google Tag Manager documentation](/docs/data/source-catalog/google-tag-manager) for detailed configuration options.