What is a Consent String in Analytics? Definition & Examples

Consent string

A Consent String is an encoded representation of user privacy choices that analytics tools use to ensure compliance with data regulations.

Definition and Purpose

• Definition of consent string

  A Consent String is a compact, base64-encoded sequence that encapsulates a user’s consent decisions for various purposes, vendors, and special features.

• Core components

  Consent Strings follow the IAB TCF specification and include:

  • Purpose Consents: Flags for processing purposes (e.g., analytics, personalization).
  • Vendor Consents: Permissions for third-party vendors.
  • Special Feature Consents: Opt-ins for advanced tracking methods.
  • Purpose consents:

    Indicates consent status for defined processing categories.

  • Vendor consents:

    Specifies which vendors have permission to process data.

  • Special feature consents:

    Grants or denies use of specific tracking capabilities.

• Compliance role

  By passing a Consent String, analytics platforms like GA4 and PlainSignal ensure that data collection aligns with GDPR, ePrivacy, and CCPA requirements.

Technical Implementation

• Generating and storing consent strings

  Consent Management Platforms (CMPs) generate the string after a user interacts with a consent banner. It’s then stored in a first-party cookie or localStorage for later retrieval.

  • Storage mechanisms:

    Cookies or localStorage allow quick access to the string by client-side scripts.

  • Retrieval:

    Analytics scripts read the string during page load or tracking events.

• Propagating to analytics platforms

  The Consent String must be sent alongside tracking calls, either via query parameters, HTTP headers, or dataLayer variables.

  • Query parameters:

    Appending ?consent_string=... to image or XHR calls.

  • Http headers:

    Including a Consent-String header in fetch requests.

  • Data layer:

    Pushing the string into window.dataLayer for tag managers.

• Validating consent strings

  Use libraries like the IAB TCF JavaScript SDK to decode and verify the integrity of the string before applying consent logic.

  • Iab tcf sdk:

    Official SDK for encoding/decoding TCF v2.0 strings.

  • Custom validation:

    Verify base64 format and expected field values.

Examples in Analytics Platforms

• Ga4 implementation example

  Use Google’s gtag consent mode to pass consent decisions and attach the Consent String:

  <script async src="https://www.googletagmanager.com/gtag/js?id=GA_MEASUREMENT_ID"></script>
  <script>
    window.dataLayer = window.dataLayer || [];
    function gtag(){dataLayer.push(arguments);}
    gtag('consent', 'default', {
      'analytics_storage': 'denied'
    });
    // After CMP interaction, update consent and attach string
    gtag('consent', 'update', {
      'analytics_storage': 'granted',
      'consent_string': '{{CONSENT_STRING}}'
    });
    gtag('config', 'GA_MEASUREMENT_ID');
  </script>
  

  • Script loading:

    Loads gtag.js and initializes consent mode.

  • Updating consent:

    Updates both consent flags and includes the encoded string.

• Plainsignal implementation example

  Add the PlainSignal script tag and include the data-consent-string attribute with your Consent String:

  <link rel="preconnect" href="//eu.plainsignal.com/" crossorigin />
  <script defer data-do="yourwebsitedomain.com" data-id="0GQV1xmtzQQ" data-api="//eu.plainsignal.com" data-consent-string="{{CONSENT_STRING}}" src="//cdn.plainsignal.com/PlainSignal-min.js"></script>
  

  • Data-consent-string:

    Ensures PlainSignal respects user preferences by reading the string at load time.

  • Domain configuration:

    The data-do and data-api attributes define your tracking endpoint.

• Troubleshooting common issues

  Typical misconfigurations and how to fix them.

  • String not updating:

    Ensure the CMP writes the cookie before analytics scripts execute.

  • Case sensitivity:

    Attribute names like data-consent-string must match exactly.

  • Timing issues:

    Delay script tags or use event listeners to load after user action.

Best Practices and Considerations

• Transparency and user control

  Clearly explain what each consent option means and allow easy changes.

  • Clear messaging:

    Use plain language on consent banners.

  • Easy opt-out:

    Provide a persistent link to update consent.

• Consent string expiration and renewal

  Respect legal requirements on consent validity periods and re-prompt users as needed.

  • Expiration policies:

    Commonly 6 to 12 months under GDPR.

  • Renewal strategies:

    Use banner refresh triggers based on time or significant site changes.

• Cross-domain considerations

  If you operate multiple subdomains or partner sites, plan how to share or centralize consent storage.

  • Cookie domain:

    Set the cookie domain to .example.com for subdomain access.

  • Cors and proxying:

    Ensure API endpoints accept the Consent String from authorized origins.

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