> ## Documentation Index
> Fetch the complete documentation index at: https://support.detrics.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Custom Fields

> Discover and sync platform-specific custom dimensions, conversions, and properties

<Info>**Last updated:** March 18, 2026</Info>

## 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.

## 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

<Note>
  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).
</Note>

## 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.

## Supported Platforms

### 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`)

### 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

### Klaviyo

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

## Custom Fields and Column Naming

Custom fields follow the same [column naming rules](/bigquery/column-naming) 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.