Certain embodiments provide systems and methods to perform in-line translation of message content according to FIX protocol variants in a trading system. An example method includes receiving, at a computing device, a message formatted according to a FIX protocol, the message including message content and a message wrapper, the message wrapper providing session and delivery information for the message to a target. The example method includes performing in-line translation of the message content of the received message to adjust the message content according to a predefined set of rules without affecting the message wrapper (with the possible exception of the message size) and message routing session. The example method includes facilitating routing of the message to the target based on the message wrapper.