There is some overlap between when you would want to use a custom field versus a tag so it can at times be unclear which you should use.
Custom fields are better suited to capture permanent data relative to a contact that is not easily changed. For example, you would use a custom field to capture a contact's name, phone number, birthdate, and more. Custom fields also have the advantage of creating personalization tags so that you can insert the data the custom field stores into your campaigns.
Tags, on the other hand are generally used for data that can quickly change. You can easily filter your list by tags so it's a great segmentation option but you can't insert the data like you can with a custom field.
To make it more clear when you'd want to use tags versus custom fields, here are some examples:
- You'd use a tag to indicate someone is an Instagram user, but you'd want to use a custom field to store their Instagram handle. That way you can create a segment of Instagram users and you could use the custom field to insert their handle into campaigns.
- You'd use a tag to indicate someone is a customer, but you'd use a custom field to store their order number.
- You'd use a tag to indicate someone downloaded a white paper, but you'd use a custom field to store the date of the download.
It should be noted that both tags and custom fields can be used as conditions when creating segments, advanced searches, "if/else" automation forks, automation goal conditions, and more when using the floating segment builder. In addition both tags and custom fields can be used as automation start triggers.