The Nexus is a series of Android smartphones and tablets produced by Google in co-operation with some phone-making companies. The purpose of the Nexus phones and tablets is to offer a "pure Android experience", in which the phones or tablets come free of carrier or manufacturer modifications and with an unlockable bootloader to allow for further development and end-user modification. Nexus phones and tablets were once considered the "flagship" Android devices. The Nexus line was later replaced with the Google Pixel.