IconVault's MAC Generator creates cryptographically random MAC addresses for lab work, testing and privacy. Generate 1 to 20 addresses at once, pick a vendor OUI from the built-in table (Apple, Cisco, Intel, Samsung, Dell, Microsoft, Google, VMware and more), or toggle the locally administered bit to produce safe test addresses that cannot collide with real hardware.

It also includes a reverse OUI lookup that identifies the vendor of any MAC address, with links out to the full OUI database. Generation uses crypto.getRandomValues and everything runs fully in your browser, nothing stored or uploaded. It is free to try (repeated use may ask for Pro).