How to show image filename instead of "Untitled" in Sanity gallery array?

Good news—you can definitely show the filename! The key is placing the preview configuration on the image object itself, not on the array field.

When you add custom fields to an image type in an array, Sanity stops showing the default filename preview. You need to explicitly tell it what to display by adding a preview configuration. Here's how:

{
  name: 'gallery',
  type: 'array',
  of: [
    {
      type: 'image',
      fields: [
        {
          name: 'alt',
          type: 'string',
          title: 'Alt Text'
        }
      ],
      preview: {
        select: {
          title: 'asset.originalFilename',
          media: 'asset'
        }
      }
    }
  ]
}

The important bits:

• title: 'asset.originalFilename' - This pulls the original filename from the image asset
• media: 'asset' - This keeps the image thumbnail visible in the list

The asset object is automatically populated when you upload an image and includes read-only properties like originalFilename, url, size, etc. You don't need to create any additional fields—just reference asset.originalFilename in your preview select.

If you want to get fancier, you can use a prepare function to customize the display even further, but for showing filenames, the simple select approach above should work perfectly.