Fg-optional-mp-files.bin | Browser |

Do not confuse fg-optional-mp-files.bin with any system-critical binary. It is purely a runtime performance aid. fg-optional-mp-files.bin is not malware. It is not a hidden log file spying on you. And it is not a broken relic of an old install. It is a well-intentioned cache that makes FlightGear’s multiplayer experience smooth—until it grows too large or corrupts.

If you have spent any time navigating the depths of your FlightGear installation directory or its associated cache folders, you may have stumbled upon a peculiar file named fg-optional-mp-files.bin . At first glance, it looks like a binary ghost—neither an executable nor a standard scenery file. For many users, this file becomes a source of confusion, especially when it grows to several gigabytes or appears to cause crashes. fg-optional-mp-files.bin

This article provides a deep dive into what fg-optional-mp-files.bin is, why FlightGear creates it, whether you can delete it, and how to troubleshoot common issues related to it. fg-optional-mp-files.bin is a binary cache file used by FlightGear’s Multiplayer (MP) system . Specifically, it is part of the fgcom (FlightGear Communications) module or the multiplayer aircraft model downloading system. Do not confuse fg-optional-mp-files

| File | Purpose | Can delete? | |------|---------|--------------| | fg-optional-mp-files.bin | Multiplayer aircraft models (3D & textures) | Yes | | terrasync_cache/ | World scenery (terrain, buildings, airports) | Yes (but will redownload) | | fgcom_voice.db | Voice chat audio recordings | Yes (loses voice history) | | .fgfsrc or autosave.xml | User preferences and joystick bindings | No (loss of settings) | It is not a hidden log file spying on you