Does the 2018 Toyota 4Runner have blind spot monitor?

Yes, a blind spot monitor is available (and typically enabled) on the base trim level of the 2018 Toyota 4Runner. It alerts You when there's a vehicle in Your blind sport, which might otherwise bypass Your attention in Your side view mirrors. You should see a BSM (blind spot monitoring) button on the dashboard, typically to the left of the steering wheel. If You press it, it'll turn the Blind Spot Monitor on, with the button itself illuminating and a pleasant chime sounding, as well as indicator lights on Your outside mirrors displaying for a few seconds as part of the system check. Now, when a vehicle is in Your blind spot area, You'll see the indicator illuminate in the relevant side view mirror.