Core libraries developed and maintained by the Elixir core team:

• Elixir (language stdlib and compiler) — https://github.com/elixir-lang/elixir
• ExUnit (testing framework) — part of Elixir stdlib (https://hexdocs.pm/ex_unit)
• Mix (build tool) — part of Elixir stdlib (https://hexdocs.pm/mix)
• IEx (interactive shell) — part of Elixir stdlib (https://hexdocs.pm/iex)
• Logger (logging) — part of Elixir stdlib (https://hexdocs.pm/logger)
• EEx (embedded Elixir templates) — part of Elixir stdlib (https://hexdocs.pm/eex)
• Code (runtime code loading/evaluation utilities) — part of Elixir stdlib (https://hexdocs.pm/code)
• OTP integration modules (e.g., GenServer wrappers, Supervisor helpers) — in stdlib (https://hexdocs.pm/elixir/GenServer.html)
• Hex (package manager, developed by the Elixir community with strong Elixir team involvement) — https://hex.pm and https://github.com/hexpm/hex
• Mix tasks and official Hex packages maintained by the team (e.g., hex, hex_core, rebar3_hex) — https://github.com/hexpm

Note: Many commonly used libraries (Phoenix, Ecto, Plug, Nerves) are developed by the broader Elixir community, not the core Elixir team. For authoritative list of core repos, see the Elixir GitHub organization: https://github.com/elixir-lang.