---
title: GA4 + Google Ads (gtag.js)
description: Send data to Google Analytics 4 and Google Ads with automatic Consent Mode v2 support.
lastModified: 2026-02-10

icon: google-analytics
---
Google Tag (`gtag.js`) is Google's unified tracking script for sending data to Google Analytics 4 (GA4), Google Ads, and Floodlight. It measures user behavior, tracks conversions, and powers Google's advertising ecosystem.

c15t initializes Google Tag with Consent Mode v2 defaults set to denied and automatically updates the consent state when users make choices. You don't need to configure Google Consent Mode yourself.

> ℹ️ **Info:**
> Use GTM if your team needs centralized tag management in the GTM UI. Use gtag.js if you only need GA4/Google Ads directly in code. Don't run both for the same destination unless intentional, or you may duplicate events.

**Choosing the right category:**

* Use `category: 'measurement'` for analytics-only tracking (GA4 events)
* Use `category: 'marketing'` for advertising and conversion tracking (Google Ads)

## Adding GA4 + Google Ads to c15t

> ℹ️ **Info:**
> See the integration overview for how to pass scripts to your framework (JavaScript, React, or Next.js).

```ts
import { gtag } from '@c15t/scripts/google-tag';

gtag({
  id: 'G-XXXXXXXXXX',
  category: 'measurement', // or 'marketing'
})
```

## Types

### GtagOptions

|Property|Type|Description|Default|Required|
|:--|:--|:--|:--|:--:|
|id|string|Your gtag id|-|✅ Required|
|category|AllConsentNames|The consent category to use for the gtag script. This is typically marketing (Ads & Floodlight) or measurement (Analytics)|-|✅ Required|
|consentMapping|Record\<string, string\[]> \|undefined|Custom mapping from c15t consent categories to Google Consent Mode v2 types. Overrides the default mapping when provided.|\`\`\`ts \{ necessary: \['security\_storage'], functionality: \['functionality\_storage'], measurement: \['analytics\_storage'], marketing: \['ad\_storage', 'ad\_user\_data', 'ad\_personalization'], experience: \['personalization\_storage'], } \`\`\`|Optional|
|script|Script \|undefined|Deprecated script-level overrides preserved for backwards compatibility. Prefer manifest-backed options instead of this generic override bag.|-|Optional|

### Script

|Property|Type|Description|Default|Required|
|:--|:--|:--|:--|:--:|
|id|string|Unique identifier for the script|-|✅ Required|
|src|string \|undefined|URL of the script to load|-|Optional|
|textContent|string \|undefined|Inline JavaScript code to execute|-|Optional|
|category|HasCondition\<AllConsentNames>|Consent category or condition required to load this script|-|✅ Required|
|callbackOnly|boolean \|undefined|Whether this is a callback-only script that doesn't need to load an external resource. When true, no script tag will be added to the DOM, only callbacks will be executed.|false|Optional|
|persistAfterConsentRevoked|boolean \|undefined|Whether the script should persist after consent is revoked.|false|Optional|
|alwaysLoad|boolean \|undefined|Whether the script should always load regardless of consent state. This is useful for scripts like Google Tag Manager or PostHog that manage their own consent state internally. The script will load immediately and never be unloaded based on consent changes. Note: When using this option, you are responsible for ensuring the script itself respects user consent preferences through its own consent management.|false|Optional|
|fetchPriority|"high" \|"low" \|"auto" \|undefined|Priority hint for browser resource loading|-|Optional|
|attributes|Record\<string, string> \|undefined|Additional attributes to add to the script element|-|Optional|
|async|boolean \|undefined|Whether to use async loading|-|Optional|
|defer|boolean \|undefined|Whether to defer script loading|-|Optional|
|nonce|string \|undefined|Content Security Policy nonce|-|Optional|
|anonymizeId|boolean \|undefined|Whether to use an anonymized ID for the script element, this helps ensure the script is not blocked by ad blockers|true|Optional|
|target|"head" \|"body" \|undefined|Where to inject the script element in the DOM. Options: \`'head'\`: Scripts are appended to \`\<head>\` (default); \`'body'\`: Scripts are appended to \`\<body>\`|'head'|Optional|
|onBeforeLoad|Object \|undefined|Callback executed before the script is loaded|-|Optional|
|onLoad|Object \|undefined|Callback executed when the script loads successfully|-|Optional|
|onError|Object \|undefined|Callback executed if the script fails to load|-|Optional|
|onConsentChange|Object \|undefined|Callback executed whenever the consent store is changed. This callback only applies to scripts already loaded.|-|Optional|
|vendorId|string \|number \|undefined|IAB TCF vendor ID - links script to a registered vendor. When in IAB mode, the script will only load if this vendor has consent. Takes precedence over \`category\` when in IAB mode. Use custom vendor IDs (string or number) to gate non-IAB vendors too.|-|Optional|
|iabPurposes|number\[] \|undefined|IAB TCF purpose IDs this script requires consent for. When in IAB mode and no vendorId is set, the script will only load if ALL specified purposes have consent.|-|Optional|
|iabLegIntPurposes|number\[] \|undefined|IAB TCF legitimate interest purpose IDs. These purposes can operate under legitimate interest instead of consent. The script loads if all iabPurposes have consent OR all iabLegIntPurposes have legitimate interest established.|-|Optional|
|iabSpecialFeatures|number\[] \|undefined|IAB TCF special feature IDs this script requires. Options: 1: Use precise geolocation data; 2: Actively scan device characteristics for identification|-|Optional|

#### `onBeforeLoad`

Callback executed before the script is loaded

|Property|Type|Description|Default|Required|
|:--|:--|:--|:--|:--:|
|id|string|The original script ID|-|✅ Required|
|elementId|string|The actual DOM element ID used (anonymized if enabled)|-|✅ Required|
|hasConsent|boolean|Has consent|-|✅ Required|
|consents|ConsentState|The current consent state|-|✅ Required|
|element|HTMLScriptElement \|undefined|The script element (for load/error callbacks) Will be undefined for callback-only scripts|-|Optional|
|error|Error \|undefined|Error information (for error callbacks)|-|Optional|

#### `onLoad`

Callback executed when the script loads successfully

|Property|Type|Description|Default|Required|
|:--|:--|:--|:--|:--:|
|id|string|The original script ID|-|✅ Required|
|elementId|string|The actual DOM element ID used (anonymized if enabled)|-|✅ Required|
|hasConsent|boolean|Has consent|-|✅ Required|
|consents|ConsentState|The current consent state|-|✅ Required|
|element|HTMLScriptElement \|undefined|The script element (for load/error callbacks) Will be undefined for callback-only scripts|-|Optional|
|error|Error \|undefined|Error information (for error callbacks)|-|Optional|

#### `onError`

Callback executed if the script fails to load

|Property|Type|Description|Default|Required|
|:--|:--|:--|:--|:--:|
|id|string|The original script ID|-|✅ Required|
|elementId|string|The actual DOM element ID used (anonymized if enabled)|-|✅ Required|
|hasConsent|boolean|Has consent|-|✅ Required|
|consents|ConsentState|The current consent state|-|✅ Required|
|element|HTMLScriptElement \|undefined|The script element (for load/error callbacks) Will be undefined for callback-only scripts|-|Optional|
|error|Error \|undefined|Error information (for error callbacks)|-|Optional|

#### `onConsentChange`

Callback executed whenever the consent store is changed. This callback only applies to scripts already loaded.

|Property|Type|Description|Default|Required|
|:--|:--|:--|:--|:--:|
|id|string|The original script ID|-|✅ Required|
|elementId|string|The actual DOM element ID used (anonymized if enabled)|-|✅ Required|
|hasConsent|boolean|Has consent|-|✅ Required|
|consents|ConsentState|The current consent state|-|✅ Required|
|element|HTMLScriptElement \|undefined|The script element (for load/error callbacks) Will be undefined for callback-only scripts|-|Optional|
|error|Error \|undefined|Error information (for error callbacks)|-|Optional|