Editing Advertising network (section)

===Based on the number of clients and traffic quality===
Ad networks can also be divided into first-tier and second-tier networks. First-tier advertising networks have a large number of their own advertisers and publishers, they have high quality traffic, and they serve ads and traffic to second-tier networks. Examples of first-tier networks include the major [[search engines]]. Second-tier advertising networks may have some of their own advertisers and publishers, but their main source of revenue comes from syndicating ads from other advertising networks.

While it is common for websites to be categorized into tiers, these can be misleading because tier 1 and tier 2 networks might perform differently based on different metrics, such as reach versus impressions.