Using Better Compatibility Checker to Verify a Server Before Joining

Reading the Compatibility Screen

When you connect to a modded server, Better Compatibility Checker intercepts the compatibility step and shows you a simple result: a green checkmark if your pack matches the server's, or a red X if it does not. This happens before you are fully in-game, so it is your first signal that something is off.

What to Do With the Result

A green checkmark means the modpack name and version strings match between your client config and the server's. You can proceed normally.

A red X means at least one of those two values differs. Before joining, note which pack version the server lists and compare it to the version you have installed. If they differ, grab the correct client build.

If you are unsure whether the mismatch is real, open your config file — config/bcc-common.toml on Forge or config/bcc.json on Fabric — and read the name and version entries. Compare them to what the server admin publishes. Matching text means the X is likely caused by the server lacking the mod, in which case the standard Forge check is being used instead.

Do not ignore a persistent X on a heavily modded server. Even when the server allows you to join, mismatched pack versions can cause missing blocks, broken recipes, or disconnects later.