Not entirely sure what you mean.
A browser is normally a piece of software running on a piece of hardware, and normally interacts with the internet (per say) with lots (most, all...?) of its communications and traffic more so from the perspective of IP addresses or even domain URLs, at an application layer.
A MAC address is more traditionally considered as tied to a piece of hardware like a network interface or wifi card in a PC, or in the case of a mobile device its wifi transmitter/receiver component, and for hardware communications at a data link layer.
Maybe you're talking about a browser that has the ability to interact with your device's hardware, to temporarily change or mask your device's MAC address for the purpose of then when the browser goes out and does its communications to the internet (per say) at the higher layer?
For most modern Android mobile versions there's already the ability to set your device to randomize it's MAC address, settable via the advance settings for each wifi network your device joins, regardless of whatever browser or apps are on the device.