Comment by ivan_gammel

> Technically you don't have to be an employed developer to become a senior developer.

Outside of a sufficiently large organization „seniority“ of a developer doesn‘t make any practical sense. So, technically you can assign yourself any label, but that would be weird thing to do.

A freelancer is measured by portfolio, a computer scientist in academia by publications, an OSS contributor by the volume and impact of contributions. In either case, it‘s proportional to the effort spent on learning and building.

Anyway, regardless of employment status the measure of your professionalism is not defined by only something you can learn from the books. Experience matters a lot: it‘s nearly impossible to succeed in stakeholder management or presentation of your solutions by reading anything. You need practice and feedback. Senior engineers aren‘t those who excel in writing code: fresh CS graduates are supposed to know algorithms better. Senior engineers can contribute at full scale of SDLC themselves and support others. That is much easier to achieve in a professional environment rather than working on amateur projects.