Is there any way to set a default value in a document field?

Yes! Sanity provides two main ways to set default values in document fields:

1. Field-Level Initial Values (Simple Defaults)

For straightforward default values, you can use the initialValue property directly in your schema field definition:

defineField({
  name: 'approved',
  type: 'boolean',
  initialValue: true
})

This works great for static defaults that should apply to all new documents of that type.

2. Initial Value Templates (Dynamic Defaults)

For more complex scenarios, Sanity has a powerful Initial Value Templates feature that lets you:

• Set dynamic values based on context
• Create multiple creation options for the same document type
• Access current user information
• Fetch data from APIs or existing documents
• Pass parameters from the creation flow

Here's an example that sets the author field to the current user:

// sanity.config.ts
export default defineConfig({
  document: {
    newDocumentOptions: (prev, context) => {
      return [
        ...prev,
        {
          id: 'article-with-author',
          title: 'New Article',
          schemaType: 'article',
          value: async (params, context) => {
            const {currentUser} = context
            return {
              author: {
                _type: 'reference',
                _ref: currentUser.id
              },
              publishedAt: new Date().toISOString()
            }
          }
        }
      ]
    }
  }
})

Initial Value Templates are especially useful for parent-child relationships, where you want to automatically set a reference to a parent document when creating a child from a specific context.

The main difference: use initialValue for simple static defaults, and Initial Value Templates when you need dynamic values, user context, or multiple creation options for the same document type.