# About 

### About `custom_fields`
Read responses (`GET /customers`, `GET /customers/{customer_id}`, and the
`customer` block of every offer) return `custom_fields` keyed by the
field's display **label** — the same label you see in the Mercura admin UI
— rather than the internal column id. Columns with no active definition
are omitted. If two custom columns share a label, the one defined first
(by display order, then creation time) wins and the other's value is
dropped from the response; deduplicate colliding columns in the admin UI.
The same label-keying applies to suppliers.
The **write** path is deliberately asymmetric: on `POST /customers` send
`custom_fields` keyed by the internal column **id** (not the label). Only
reads are label-keyed.

Version: 1.79.2

## Description:

  - `About custom_fields` ()
    Read responses (`GET /customers`, `GET /customers/{customer_id}`, and the
`customer` block of every offer) return `custom_fields` keyed by the
field's display **label** — the same label you see in the Mercura admin UI
— rather than the internal column id. Columns with no active definition
are omitted. If two custom columns share a label, the one defined first
(by display order, then creation time) wins and the other's value is
dropped from the response; deduplicate colliding columns in the admin UI.
The same label-keying applies to suppliers. The **write** path is deliberately asymmetric: on `POST /customers` send
`custom_fields` keyed by the internal column **id** (not the label). Only
reads are label-keyed.