Every MCP server talks to its client over a transport, and in 2026 there are three names you'll meet: stdio, HTTP+SSE and Streamable HTTP. Picking the right one isn't subtle once you know what each is for — but choosing wrong (or staying on the deprecated one) is a common, avoidable source of pain. Here's the comparison that settles it.
stdio — local and simple
stdio is the transport for servers running on the same machine as the client. Your client launches the server as a child process — an npx or uvx command in the config — and they speak JSON-RPC over standard input and output. There's no network, no ports, no auth handshake, and nothing to host. That makes it the right default for personal, local servers: a filesystem server, a local database, anything where the server and the AI app live on one box. It's the simplest thing that works, and for a huge share of setups it's all you need. See MCP config file location for where these commands live.
HTTP+SSE — the deprecated remote option
The original remote transport used HTTP with Server-Sent Events: two endpoints, one holding a long-lived SSE stream open for server-to-client messages, the other taking client POSTs. It worked, but it aged badly — a persistent socket per client is expensive and fragile, a network blip drops the stream, and two SSE servers behind a load balancer produce split-brain state because session data on one is invisible to the other. It's now deprecated, and vendors are actively switching it off. If you're on it, you're on borrowed time — the full story is in SSE deprecated: migrate to Streamable HTTP.
Streamable HTTP — the modern remote transport
Streamable HTTP is the replacement and the right choice for any new remote server. It collapses the old two-endpoint design into a single MCP endpoint that handles both POST and GET, with no persistent socket to babysit. Crucially, it's built to be stateless: with the new Mcp-Method routing headers and cacheable results from the 2026-07-28 spec, a Streamable HTTP server runs behind a plain load balancer like any web service. That's what makes it scale — and why the stateless migration is the path everyone's on.
How to choose
The decision tree is short. Server and client on the same machine, single user? Use stdio — don't overthink it. Server needs to be reached over the network, by a hosted client like ChatGPT, or by many users? Use Streamable HTTP, with OAuth and proper hosting. Already running HTTP+SSE? Treat that as a migration task, not a steady state, and move before a vendor deadline forces it. The only genuinely wrong answer in 2026 is building something new on SSE.
Going further
Transports decide how your server is reached; for what to build, start with what is an MCP server and build your first MCP server in Node.js. For scaling remote deployments, read enterprise MCP gateway deployment. More in the developer-tools category.