The first rung on a ladder the industry never formally standardised — every company draws the line between “junior” and “mid-level” slightly differently.
A junior developer is usually 1–3 years into their career, competent in one or two languages, and working on well-scoped tasks with code review and guidance from more senior engineers — the period where the job is mostly about building fluency rather than owning outcomes. There’s no accrediting body or formal certification behind the title; it’s an informal convention that varies company to company, sometimes formalised into numbered “IC” (individual contributor) levels at larger tech firms.
Worth flagging plainly: no peer-reviewed literature defines this term — it’s industry convention, sourced from practitioner and HR-industry writing rather than academic study, and that’s a fine, honest place for a term like this to sit.