Sailthru Horizon
316 websites

Sailthru Horizon is free to use

http://getstarted.sailthru.com/

Third, enter your full Horizon subdomain, i.e. horizon.yourdomain.com, under the "Horizon Subdomain" field in your Sailthru account settings.

VS

Think Realtime
10,155 websites

Think Realtime costs money

http://www.thinkrealtime.com/

The worlds most advanced real time advertising. Industry leaders work with Think Realtime.

Market Share by Top Websites

1 Think Realtime is leading in Top 1M Sites and The Entire Web.

2 Sailthru Horizon is leading in Top 10K Sites and Top 100K Sites.

Websites Categories

1 Sailthru Horizon has better usage coverage in more websites categories. Including News & Media, Food & Drink, Arts & Entertainment, Travel & Tourism and 17 other categories.

2 Think Realtime is leading in Vehicles.

Geography

1 Think Realtime is leading in most countries, including United States, Canada, Philippines, India and 47 other countries.

2 Sailthru Horizon is leading in Hungary, Italy, Taiwan, Switzerland and 3 other countries.