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Last updated: March 18, 2026

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What Are Custom Fields?

Most platforms offer a standard set of metrics and dimensions that every account has access to (e.g., spend, impressions, campaign_name). But some platforms also support custom fields — user-defined metrics or dimensions specific to individual accounts. Examples of custom fields:
  • Google Analytics 4 — Custom dimensions and custom metrics you’ve defined in your GA4 property
  • Meta Ads — Custom conversions, custom events, and offline event sets
  • Klaviyo — Custom conversion metrics tied to your flows and campaigns
  • HubSpot — Custom properties defined on your contacts, companies, deals, and other CRM objects
Detrics can discover these fields per account and sync them alongside standard fields in your BigQuery tables.

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How Custom Field Discovery Works

  1. When editing a table, click Load Custom Fields in the field picker
  2. Select an account from the dropdown — custom fields are discovered per account since each account may have different custom fields
  3. Detrics queries the platform API to discover available custom fields
  4. Custom fields appear in the field picker alongside standard fields, marked with a special badge
  5. Select the custom fields you want to include in your table
The account you select for discovery is only used to find available fields — it doesn’t affect which accounts the transfer syncs. When the transfer runs, Detrics syncs all selected accounts (or all accounts, depending on your setting).

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Multi-Account Handling

When a transfer syncs multiple accounts, some accounts may have custom fields that others don’t. Detrics handles this gracefully:
  • If Account A has custom dimension user_segment but Account B doesn’t, the column still exists in BigQuery
  • Rows from Account A will have values for user_segment
  • Rows from Account B will have NULL for that column
  • BigQuery handles sparse columns natively — no performance impact
This means you don’t need to worry about field compatibility across accounts. Include whatever custom fields you need, and Detrics will populate them where available.

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Supported Platforms

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Google Analytics 4

GA4 supports custom dimensions and custom metrics that you define in your property settings. These appear in Detrics with their configured parameter name. Custom dimensions commonly used:
  • User-scoped dimensions (e.g., user_type, membership_level)
  • Event-scoped dimensions (e.g., content_category, product_brand)
Custom metrics commonly used:
  • Event count metrics (e.g., custom_purchase_value, video_completions)

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Meta Ads

Meta Ads supports custom conversions that track specific actions on your website or app. These appear as additional conversion metrics in the field picker. Examples:
  • Custom conversion events mapped to specific pixel events
  • Offline conversion sets

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Klaviyo

Klaviyo supports custom conversion metrics tied to your flows and campaigns. These track specific revenue or engagement actions.

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Custom Fields and Column Naming

Custom fields follow the same column naming rules as standard fields. Field names are normalized to snake_case in BigQuery. For example, a GA4 custom dimension called UserSegment becomes user_segment in your BigQuery table.