AppNexus
1,380,787 websites

AppNexus offers both free and paid options

http://www.appnexus.com

AppNexus is the most advanced platform for buying real-time online advertising. AppNexus's clients include the largest ad networks and online advertisers. AppNexus offers a proprietary gateway to premier ad exchanges and ad inventory aggreg...

VS

OpenX
1,474,014 websites

OpenX costs money

http://openx.com

OpenX is one of the world's leading providers of digital and mobile advertising technology, enabling businesses to manage and maximize their ad revenue. OpenX products, including OpenX Enterprise, OpenX Market and OpenX Lift provide a compr...

Market Share by Top Websites

1 OpenX is leading in The Entire Web.

2 AppNexus is leading in Top 10K Sites, Top 100K Sites and Top 1M Sites.

Websites Categories

1 OpenX has better usage coverage in more websites categories. Including Arts & Entertainment, Science & Education, Computers Electronics & Technology, Games and 11 other categories.

2 AppNexus is leading in Travel & Tourism, Health, Vehicles, Lifestyle and 5 other categories.

Geography

1 OpenX is leading in most countries, including Japan, Russia, Taiwan, Italy and 81 other countries.

2 AppNexus is leading in United States, France, United Kingdom, Germany and 71 other countries.