The older Raspberry Pi's (Pi 1, Pi 2 and Pi Zero) couldn't boot from a USB-device, but the [Raspberry Pi 3 has support for it][1]. The Pi and Pi 2 have semi-support for it ([using an SD-card with a single bootfile][2]). The Pi Zero W is a remake of their older boards but it's newer than the Pi 3.

Is the Raspberry Pi Zero W fully compatible with the new bootcode? Can the Raspberry Pi Zero W boot from USB without using an SD card?

[1]: https://www.raspberrypi.org/blog/pi-3-booting-part-i-usb-mass-storage-boot/
[2]: https://github.com/raspberrypi/documentation/tree/master/hardware/raspberrypi/bootmodes#special-bootcodebin-only-boot-mode