# Changing a field name

https://www.sanity.io/learn/course/handling-schema-changes-confidently/changing-a-field-name.md

Rename fields by first deprecating existing ones and marking them read only

Open an event document. There you will find the “Event Type” field that describes if the event is “In-person” or “Virtual.” When you go to the “Inspect” menu (`ctrl+opt+i/ctrl+alt+i`), you see that it’s encoded 

```json
{
  // ...other fields
  eventType: "in-person"
}
```

Let’s pretend that you have received feedback from your developer colleagues that it’s a bit confusing to have both a **document type** called `event` and a **field type** called `eventType` (they're correct by the way, who modeled this schema?)

When implementing this data in an application, you also get a somewhat inelegant pattern: `event.eventType`. 

Naming is hard.

We want to change this field to be called “Event Format” instead, that is a `format` attribute in the JSON data so that you can get the value with `event.format` where this field content is used.

## Change management

Now, you will not only change this field as data for developers, but you are changing it for content creators as well. Usually, if it’s early in the project, and there aren’t a lot of documents yet, you can get away with just changing the `name` property of the field and manually backfilling the content. 

But let’s pretend that this is a more mature project, where you have an application in production that consumes and depends on this data, and you (or someone on your team) don’t want to spend time manually going through every document to copy-paste content between the old and the new field.

In this case, changing the field name requires the following steps:

* Adding a new field with the new name
* Deprecating the old field
* Adapting a query to support the new field name and fallback on the old
* Create a content migration to move the content

## Add the new field

Begin with adding the new field; you can copy-paste the `eventFormat` field definition, and change the name.

1. **Update** the `event` document schema type to include the new `format` field

```typescript:apps/studio/schemaTypes/eventType.ts
defineField({
  name: 'format',
  type: 'string',
  options: {
    list: ['in-person', 'virtual'],
    layout: 'radio',
  },
}),
```

You should now have two identical fields with different names and labels:

![Missing alt text](https://cdn.sanity.io/images/3do82whm/next/552d1c2f4eb5d256cee08b74263c0bf284363619-602x294.png)

## Deprecate the current field

Now, you can **deprecate** the “Event type” field and add a guide for the content creator. You can also set it to “read-only” to prevent content creators from using it.

1. **Update** the `eventType` field to include config for `deprecated` and set to `readOnly`

```typescript:schemaTypes/eventType.ts
defineField({
  name: 'eventType',
  type: 'string',
  deprecated: {
    reason: 'Use the "Event format" field instead.'
  },
  readOnly: true,
  options: {
    list: ['in-person', 'virtual'],
    layout: 'radio',
  },
}),
```

Save the change and confirm that the document form now looks like this:

![Missing alt text](https://cdn.sanity.io/images/3do82whm/next/4904d5820b47e3521a92b414f6cba4e5d1acd2d4-2000x1068.png)

This prevents authors from making any further changes to this field in the Studio, or any new documents with this value.

Let's update our front end to consume the new field, once it has values.