Quick definition · 2 min Coding term
Port
A port is the numbered “door” on your computer (the 3000 in localhost:3000) that a running app uses to talk to your browser.
Think of it like
Apartment numbers in one building. The building is your computer; the port number says which app to knock on.
Example
You will see ports in preview links, and sometimes a “port already in use” error, which just means another app is using that door.
Why it matters
Ports show up in every local preview link and in confusing errors, with no explanation of what they are.
Where you’ll see it
localhost linksyour dev server
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