> ## 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.

# Constant field

> A computed field that writes the same fixed value to every record.

<Info>
  The Constant field always resolves to one fixed value you configure. Every record gets the same value, and submitters never type it.
</Info>

Constant is a **computed** field. Its value is system-generated from the setting you configure, the field is always required, and it does not appear as an input a submitter can fill in.

## When to use it

Reach for Constant when the same value belongs on every record:

* A fixed label such as a source-system name, a channel, or a version tag.
* A constant segment inside a [Concatenation](/reference/fields/concatenation) field, so you do not retype it on every submission.
* A marker that tells records produced under one model apart from another.

<Warning>
  Do not use Constant when the value differs between records. Use a [Dropdown](/reference/fields/dropdown) for a controlled set of choices, or [Text](/reference/fields/text) for free input.
</Warning>

## How it works

Every record gets the configured `value`, identical across all of them. Because the value is generated for you, the field is not shown as an input in the submission form.

## Settings reference

| Setting | Required | Default | Description                               |
| ------- | -------- | ------- | ----------------------------------------- |
| `value` | Yes      | None    | The fixed string written to every record. |

## Example

A `channel` field on a Campaigns taxonomy, used to fold a fixed UTM value into a tagged URL:

```yaml theme={null}
name: channel
type: constant
settings:
  value: "newsletter"
```

Every campaign record created while this model is published gets `channel = newsletter`. A [Tagged URL](/reference/fields/tagged-url) field can then read this value into its `utm_medium` parameter without anyone retyping it.

## Gotchas

* **Changing `value` does not backfill.** Existing records keep the value they had when they were approved. Editing the setting and publishing again affects only new submissions.
* **It is the same on every record.** That is the point. If you need variation, this is not the right field type.
* **It is read-only.** The value is generated for you and there is nothing to edit in the submission form.

## Related

* [Fields](/reference/fields)
* [Concatenation field](/reference/fields/concatenation): combine a constant with other field values.
* [Tagged URL field](/reference/fields/tagged-url): feed a constant into a query parameter.
* [Other computed fields](/recipes/other-computed-fields)