noun
social networking site
A website or service for building social networks; often abbreviated as SNS (ソーシャル・ネットワーキング・サービス).
新しい交流サイトに登録した。
I signed up for a new social networking site.
SNS is the common abbreviation for 'social networking service' and is used more broadly than 交流サイト, which specifically emphasizes the site aspect.
Compound of 交流 (こうりゅう, 'exchange; interaction') and サイト ('site'), a direct translation of 'social networking site'.