witter co-founder Ev Williams revealed that Twitter generates 19 billion search queries a month, outranking Yahoo and Bing.

Speaking at the Twitter Chirp conference last week, Williams said that Twitter handles 600 million queries per day, or 19 million per month. Though this number is less than a quarter of what the market leader Google does on a monthly basis, 19 billion does out rank Yahoo and Bing, which generate 9.4 billion and 4.1 billion searches a month respectively, reports SearchEngineLand.com.

Most of Twitter’s searches happen outside Twitter, which is why it has traditionally been overlooked. The majority of Twitter searches happen through third-party API requests, largely through TweetDeck and Seesmic. Searches conducted through Bing and Google aren’t counted, as they archive Tweets and look them up in the same way they do conventional websites.

Rating services such as comScore don’t usually cover Twitter, which is why the volume of queries may come as a bit of a surprise.

With the launch of TweetUp and Promoted Tweets last week, Twitter search engine optimization (SEO) is rapidly becoming a hot topic among marketers.