stdio transport
stdio transport is the most common way Claude Code talks to an MCP server: the server is launched as a local subprocess, and messages pass over its standard input and output streams instead of a network socket. There is no port to open and nothing to expose to the network.
Why it matters
Because the server only exists as long as the subprocess runs, and only Claude Code's own process can write to its stdin, stdio servers are naturally local-only. The alternative, an HTTP-based transport, is used for servers that run on a remote machine.
Does stdio mean it only works in a terminal?
No, it refers to how the two processes exchange messages internally, not to how you interact with anything.
Is stdio slower than a network connection?
No, it is a local pipe, so it is typically faster than a network round trip.
Related
Looking for a different way to manage your keys? See the best Claude Code API key manager alternatives, or browse every term in the glossary.