As an account admin, you might want to have total control over some important data. Information that you don’t want anyone else to tamper with can be marked as read-only. Once a field is made read-only, only you can edit the field using your API Key.
To mark a field as read-only,
Login to Freshsales as an administrator.
Go to Admin settings > Lead/Contact/Account/Deal Module> Add Fields.
You can make a field read-only either while adding a new field(custom fields) or editing one (default and custom fields). To edit a field, click the Edit icon of the field from the custom field list.
In the Add Field/ Edit Field overlay, you can enable the Mark this field as read-only checkbox.