How to Set Up Netplay for Online Retro Multiplayer

RetroArch’s netplay is built on the same rollback mechanism covered in rollback netcode, letting two (or more, for supported cores) players connect over the internet or a local network and play a session together. This walks through hosting a session and connecting to one.

Step 1: confirm both players are using matching cores and content

This is the single most common reason netplay connections fail before ever reaching an actual network problem: netplay requires both sides to run the same core (ideally the same version) and, in most cases, the same game file. Confirm this explicitly before troubleshooting anything else:

Information → Core Information → [note the exact core name/version]
Information → Database → [or check file properties for the exact
                            ROM/ISO being loaded]

A mismatched core version can connect and then desync partway through a session — annoying enough that it’s worth confirming both sides matches upfront rather than discovering it mid-game.

Step 2: host a session

Load your content first, then:
Main Menu → Netplay → Host → Start Hosting

Hosting after content is already loaded (rather than before) ensures the exact game state at session start matches what netplay expects to synchronize from.

Step 3: configure port forwarding if hosting over the internet (not a local network)

Settings → Network → check "Netplay TCP Port" (default 55435)
Router configuration: forward that TCP port to the hosting machine's
                       local IP address

This step is unnecessary for players on the same local network, but required for internet play unless using a relay/matchmaking option that avoids direct connections (see Step 5).

Step 4: connect as the joining player

Main Menu → Netplay → Connect to Netplay Host → [enter the host's
             IP address and port]

The joining player also needs the exact same content file and core loaded, matching what the host confirmed in Step 1.

Step 5: use a relay server if port forwarding isn’t practical

Settings → Network → Use Relay Server: ON

A relay server routes traffic between both players without either side needing to open an inbound port — trading a small amount of added latency (traffic now takes an extra hop through the relay) for avoiding router configuration entirely. This is a reasonable default for players not comfortable configuring port forwarding.

Step 6: adjust input delay if the connection is inconsistent

Settings → Network → Netplay Input Latency Frames

RetroArch’s netplay uses the same rollback approach described in rollback netcode to hide latency automatically, but on a poor connection with frequent large corrections, adding a small amount of fixed input delay here can trade a bit of the rollback effect for a steadier, more predictable feel.

Step 7: verify synchronization before playing seriously

Watch the netplay status indicator for a few seconds after connecting, confirming both sides show as synchronized rather than stalled — a session that fails to fully synchronize will show clear, immediate signs (frozen input, a persistent “connecting” state) rather than working normally and failing later.

Why the core/content match matters more than the network setup

Port forwarding and relay servers get most of the troubleshooting attention because they’re the unfamiliar part, but a mismatched core version or a different ROM revision between host and joiner causes far more real-world netplay failures — and produces confusing symptoms (a connection that succeeds but immediately desyncs) that look like a network problem even though the network itself is working exactly as configured.