[Update 2/17/2014: Based on developer feedback, we have moved the date of this change back to March 3, 2014.]

We're making a change to how the contentBid setting works in “Display Network Only” campaigns. Here's some background on the change and how it might affect you.

Currently, if you have a campaign that targets only the Display Network, then you can use a CpcBid at the adgroup level to specify a default bid and a display network bid override for content networks. In the past, we've allowed users to specify a contentBid in a "Display Network Only" campaign type, even though contentBid is useful only for "Search & Display Networks" campaign type. This allowed users to switch between "Search & Display Networks" and “Display Network only” campaign types without modifying their bids.

Since display campaigns have become so much more specialized over time, we've recently removed support for switching “Display Network only” campaigns to other campaign types. This makes contentBid setting obsolete for “Display Network only” campaigns, so we are removing the ability to set contentBid for “Display Network only” campaigns in AdWords API. The default bid value will be used for serving your ads on Google Display Network.

What this means for you

If you do not set contentBid at the adgroup level for a “Display Network only” campaign, this change will not affect you.

Starting on February 18th, 2014, if you set contentBid for a “Display Network only” campaign, then you will start receiving a ReadOnlyError.READ_ONLY error for all versions of the API. You can use the fieldPath of the ApiError object to identify the operation triggering the error.

To avoid getting errors, you should:
  • modify your code to set the default adgroup bid instead of contentBid
  • clear out the contentBid field to make sure that AdWords will start using the default adgroup bid when serving your ads
  • if you store campaigns in a local data store, re-sync your data store with AdWords to pick up the updated default bid values
If you're still using contentBid to set ad group display bids in “Display Network only” campaigns within a few days of February 18th, 2014, we plan to do a one-time migration of those bids to become your ad group default bid. This migration is intended to ensure your ads serve with the correct bid; you must still make sure your code is able to handle ad group bids on the Display Network properly.

If you have any questions about this change or the AdWords API in general, you can post them on our developer forum. You can also follow our Google+ page for updates about the AdWords API.