Are social media websites like Facebook, Twitter, etc. are SaaS? Are search engines like Yahoo, Google, etc. are SaaS? Messaging applications like WhatsApp, Facebook messenger etc are SaaS? And how?
“SaaS” has, like “Cloud”, become a term that no longer really reflects its current meaning. Time marches on and while “SaaS” used to be a term that differentiated web software from downloaded or on-prem business software, that on-prem/download world has shrunk almost to irrelevance. Thus, the term’s meaning has marched on with time.
Of course Facebook, Twitter, etc. are software-as-a-service, provided over the internet.
But the definition / line for “SaaS” is applications whose business model is primarily a subscription fee for software.
Similarly, ecommerce companies are generally not “SaaS”. They do have primarily a subscription model (unlike Facebook or Twitter) but the fee is for physical goods.
There are companies a bit in the middle that may feel consumer-y like Slack, but while the free version of Slack has incredible traction, Slack’s business model is clearly in its ARR and the fees its charges for the paid versions.