Jupyter's default port, and the second-most-common "just give me an HTTP port" number after 8080.
Starting a Jupyter notebook or JupyterLab server opens a browser at http://127.0.0.1:8888 by default, which is why 8888 turns up on data-science laptops and GPU boxes. IANA's registration is ddi-tcp-1 (NewsEDGE server), which you will never meet. Otherwise 8888 is a generic HTTP alternate chosen by proxies, container images, and hand-rolled services. A notebook server is the case that matters: it executes arbitrary code as the user who started it.
Do not expose
A reachable Jupyter server is remote code execution by design — token or password auth is the only thing between a visitor and your shell, so keep it on loopback or behind an authenticated proxy or SSH tunnel.
$ curl -sI http://127.0.0.1:8888/Seen this on your network? Beige Box scans your Wi-Fi and shows every open port on every device — and its Ports tool links straight back here.
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Corrections or a missing port? Reply @rimrocksystems.