Apple released the combo updater for macOS High Sierra 10.13.4 on Friday. The combo updater is a 2.49GB download and contains everything in the macOS Sierra 10.13.4 released on Thursday, along with all the updates since High Sierra’s inaugural 10.13.0 release back in the fall.
Apple also released the incremental updater for macOS High Sierra 10.13.4 on Friday. This one clocks in at 2.38GB, just 110MB less than the full combo updater. This incremental updater will only update a Mac from 10.13.3 to 10.13.4, whereas the combo will update from anything running any prior build of High Sierra.
Apple is recommending that all users update to 10.13.4, and we’re recommending that if you’re going to manually download and apply the update, you do so with the combo. If you updated through the Mac App Store already–and assuming everything is running fine for you–you do not need either of these downloads.