It may work for a while but eventually you'll probably see a decrease in earnings as competition suffers. I did it a few times over the summer, a couple weeks at a time, and ctr did improve for that time but cpc gradually dropped off and I had to stir things up again to bring it back up.

I've tested it over and over and it varies (my sites are seasonal and the summertime travel image ads do well with me) but at the end of the day (and after millions of impressions) what works best for me is to set it to text and images and just Google do what it will.

I could never see how some claim a benefit from text only ads as they surely reducing the bid competition.

I only go text only if there is danger of G serving a display ad that looks like something else on the page (eg an affiliate ad).

I run text ads only for both the sites I manage. After extensive testing, text ads only works best for me. Now that may be a function of my page design - who knows. I'm also in such competitive consumer industries that there are so many advertisers that not being opted into all ad types never showed proof of leaving money on the table by going text only. Every sites is different and over the last 4+ years there have been some months when all ad types resulted in better earnings. But that was the exception.

A few months ago G suggested I do an experiment to test text only ads on one channel on my site. I did, and text only beat text/image by a WIDE margin. So I set that channel to text only. Then I tried it on another channel, and got same results, so I set that channel to text only. Then I tried a third channel, and got the same results.

These three channels earn the most for me, and always have.

But over the years I've tried text only vs text/image a number of times and it seems to go back and forth as to which is the highest earning setting, so who knows what the future will bring.

Right now I'm liking the money the way it is. If that changes, so will the settings. It's so easy to change these settings now that's it's not a big deal.

On a smaller channel where I have two ad spots on a page I set one to text only and one to image only to avoid duplicates ads showing, works for me.

I accept what you say - I just cant follow the logic

I just cant follow the logic

I can't either,

but I can follow the money :)

denisl - wait...are you saying AdSense is logical? Maybe 2+ years ago - now it's all tinkering and you can't run real tests even if you wanted to.

Well....yes. Its just that their aims may not always what we would like.

But if they say that there is more competition for the ad if you enable display ads together with text (in the same way that some sizes enable more competition) I don't see how you can get a better return from text only.

You can get a better ROI from text only for multiple reasons. But the most common is that my CTR with text only is 2-3x higher than with all ad types. And for me, having all ad types does not increase the cpc anywhere near 2-3x so basic math proves for my sites that text only is the best ROI for me. Few things in life are guaranteed - being opted into all ad types is by no means a guarantee of best earnings. Do your own testing - don't just believe what Google wants you to do. There are do many reasons Google wants all publishers to opt into all ad types but that's a whole other topic.