Google Publisher Tag
545,414 websites

Google Publisher Tag is free to use

https://support.google.com/dfp_premium/topic/28788?hl=en&ref_topic=28149

Google Publisher Tag (GPT) is an ad tagging library with which you can dynamically build ad requests. GPT takes key details from you such as ad unit name, ad size, and custom targeting, builds the request, and displays the ad on web pages o...

VS

Kargo
149,099 websites

Kargo offers both free and paid options

http://www.kargo.com/

Mobile first high tech ad publisher.

Market Share by Top Websites

1 Google Publisher Tag is leading in Top 10K Sites, Top 100K Sites, Top 1M Sites and The Entire Web.

2 In terms of market share, Kargo is clearly lagging behind, losing to Google Publisher Tag in all segments.

Websites Categories

1 Google Publisher Tag has better usage coverage in more websites categories. Including Arts & Entertainment, Computers Electronics & Technology, Games, News & Media and 20 other categories.

2 Kargo hasn't got a lead over Google Publisher Tag in any websites category.

Geography

1 Google Publisher Tag is leading in most countries, including United States, Japan, Taiwan, France and 160 other countries.

2 Kargo is leading in Virgin Islands, U.S. and French Guiana.