"The installer is damaged" error— Big Sur

I was able to install Big Sur only after turning off the firmware password.

This was my problem too, I turned off the firmware password, then created a boot disk. Wiped the drives and installed Big Sur. Seemed to do the trick. This was on a 2015 MacBook Pro.

Thanks for the hint. I have a 2020 Intel Mac mini. The Big Sur installer always came up with the same message. The Corsair Vengeance DIMMs worked fine with Catalina and even the diagnostic tool didn't report any errors. After putting the original DIMMs in the Big Sur upgrade went through without a problem.

I have 35 years experience with Macintosh, I have 2 machines from 2014 on Big Sur list. iMac and mini. Mini is updated fine. iMac I have wrestled with for 2+ days , 2-3 hrs on phone with Apple. Tried everything, Reset PRAM, Safe mode, Recovery , Disk Utility. Finally erased internal drive, Command R to install a new Catalina, used Time machine to restore data. Now same problem, Installer runs for a minute (15 minutes remaining) then throws exact alert "Installation cannot proceed because the installer is damaged". Downloaded and deleted/copied Installer at least 20 times. No joy. Cannot build a startup disk either, tried 2 different USB drives, Disk can't be blessed. Open to ideas.

The same issue here... before 3 new installs on the MacBook Pro 2015, download ok, first step of install ok, reboot... dead.. no files to be found - ... no access to the harddisc (SSD)... and after multiple reinstalls, now I get installer is damaged... what a crappy upgrade is this! I think Apple want to lose apple users.... On the Catalina version, I had to find a solution for the iCloud process issue that made my processor heating up... ...

I finally found a solution. Holding the “D” key, gives a hardware diagnostic. It told of a problem with a DIMM, on a 2014 imac. Purchased a new pair of DIMMs, Big Sur went right in. I would have thought 2-3 hrs on Apple tech support might have known this.

Same issue here.

Same problem here I can’t install big sur

the error start at 15minutes remaining and am sure its not the installer thats broken because I downloaded them alot

I have tried with a bootable drive .. no joy.

I have having issues installing Big Sur on my MacBook Pro 13 2014

Try booting into recovery mode (restart your Mac while holding Cmd+R) and then restarting again - this fixed a similar issue for me.