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

# Fields

> Fields are the columns of a governance model. Each has one immutable type that decides whether you enter its value or the system computes it.

A field is one piece of campaign metadata in a governance model, such as Campaign Name, Source, or Short URL. Think of fields as the columns of your taxonomy: you define each field once, then place it into one or more taxonomies, where it becomes a column people fill in.

Every field has a **type**, chosen when you create the field. The type decides how the value is captured, which settings you can configure, and whether the field is entered by a person or computed by Terminus Hub. The type cannot be changed after the field is created, so pick it deliberately.

<Info>
  Fields split into two groups. **Entered** fields are filled in by whoever makes a submission. **Computed** fields are generated by Terminus Hub from other fields or from system rules, so submitters never type their value directly.
</Info>

## Field type matrix

There are 12 field types. Four are entered, eight are computed.

| Type                                             | Entered or computed | What it is for                                 |
| ------------------------------------------------ | ------------------- | ---------------------------------------------- |
| [Text](/reference/fields/text)                   | Entered             | Free text: campaign names, codes, descriptions |
| [URL](/reference/fields/url)                     | Entered             | A web address, the base for link fields        |
| [Date](/reference/fields/date)                   | Entered             | A calendar date in a format you choose         |
| [Dropdown](/reference/fields/dropdown)           | Entered             | A choice from a picklist                       |
| [Concatenation](/reference/fields/concatenation) | Computed            | Joins the values of other fields               |
| [Tagged URL](/reference/fields/tagged-url)       | Computed            | A base URL plus query parameters               |
| [Short URL](/reference/fields/short-url)         | Entered or computed | A short link over a destination URL            |
| [QR code](/reference/fields/qr-code)             | Computed            | A QR code from another field                   |
| [Auto number](/reference/fields/auto-number)     | Computed            | A sequential number per field                  |
| [Random](/reference/fields/random)               | Computed            | A random string                                |
| [Constant](/reference/fields/constant)           | Computed            | A fixed value, the same on every record        |
| [Terminus ID](/reference/fields/terminus-id)     | Computed            | A unique identifier per record                 |

Short URL is listed as both because its slug can be auto generated (computed) or typed by a submitter (entered), depending on its slug mode. See the [Short URL](/reference/fields/short-url) page.

## Browse the field types

<CardGroup cols={2}>
  <Card title="Text" icon="text-cursor-input" href="/reference/fields/text">
    Free text with optional length, character, and case rules.
  </Card>

  <Card title="URL" icon="link" href="/reference/fields/url">
    A web address; the base for Tagged URL and Short URL.
  </Card>

  <Card title="Date" icon="calendar" href="/reference/fields/date">
    A calendar date rendered in a format you control.
  </Card>

  <Card title="Dropdown" icon="list" href="/reference/fields/dropdown">
    A choice from a picklist, with optional cascading.
  </Card>

  <Card title="Concatenation" icon="combine" href="/reference/fields/concatenation">
    Joins other fields together with a separator.
  </Card>

  <Card title="Tagged URL" icon="tags" href="/reference/fields/tagged-url">
    A base URL with query parameters appended.
  </Card>

  <Card title="Short URL" icon="scissors" href="/reference/fields/short-url">
    A short redirect link over a destination URL.
  </Card>

  <Card title="QR code" icon="qr-code" href="/reference/fields/qr-code">
    A QR code generated from another field.
  </Card>

  <Card title="Auto number" icon="hash" href="/reference/fields/auto-number">
    Sequential numbers, padded to a fixed width.
  </Card>

  <Card title="Random" icon="shuffle" href="/reference/fields/random">
    A random string of a length you set.
  </Card>

  <Card title="Constant" icon="lock" href="/reference/fields/constant">
    A fixed value, identical on every record.
  </Card>

  <Card title="Terminus ID" icon="fingerprint" href="/reference/fields/terminus-id">
    A unique identifier generated per record.
  </Card>
</CardGroup>

## Settings shared by every field

Beyond the type-specific settings, each field carries a small set of shared attributes:

* **Name.** The display name. Required, and unique within the governance model.
* **Description.** Help text shown to submitters under the field.
* **Required.** A submission with this field blank cannot be approved. Computed fields are always required, and the toggle is locked.
* **Hidden.** Only computed fields can be hidden. A hidden computed field still generates its value, but does not appear in the submission form.
* **Prefix and suffix.** Literal text wrapped around the value. Not available on URL, Tagged URL, Short URL, QR code, or Terminus ID fields.

## Reusing a field across taxonomies

A field is defined once and then referenced into a taxonomy, where it gets a position (its column order). A taxonomy can override a field's `required` and `hidden` flags, but only in the stricter direction: it can promote a field to required or hidden, never relax a field that the definition already marks required or hidden. For dropdown fields, a taxonomy can also filter which picklist options are offered.

See [field reference overrides](/reference/field-reference-overrides) for the override rules and option filtering.

## Cross-field references stay in one model

When a field references another field (Concatenation, Tagged URL, Short URL, QR code, or a cascading Dropdown), the referenced field must live in the same governance model. A reference to a field in another model is rejected. A field that is referenced by a taxonomy cannot be deleted until you remove it from those taxonomies.

## Related

* [Concepts: the data model](/concepts/data-model)
* [Concepts: the submission pipeline](/concepts/submission-pipeline)
* [Picklists reference](/reference/picklists)
* [Field reference overrides](/reference/field-reference-overrides)