Closed
Description
The only way I could get ESP8266FS.jar working on windows was to put the esptool and mkspiffs executables in the root of the esp8266 tools folder.
The path in question being {runtime.platform.path}/tools/ which resolves to C:\Program Files (x86)\Arduino\hardware\esp8266com\esp8266\tools
After doing this, the Arduino IDE upload function worked without errors.
I'm not sure if this is an issue with ESP8266FS.jar or the IDE.