Zawinski’s law
Zawinski’s law holds that every computer program attempts to expand in capability until it can read email, and those programs that cannot so expand are eventually replaced by ones that can.
The law is attributed to Jamie Zawinski, an early Netscape and Mozilla developer, who made the remark in a 1990s Usenet discussion.
The law is a satirical exaggeration of a real tendency for successful software to accumulate features well beyond its original scope. Users push for new functionality that would otherwise require them to switch to an alternative program, and each feature request seems individually reasonable to the team maintaining the program. Email reading was, at the time, an emblematic example of such scope creep, turning up in all sorts of tools that had no obvious business handling mail.
The law is a comment on the phenomenon of software bloat and is closely related to Wirth’s law.