Big Sur Installer: "An error occurred loading the update."

As @ a brody has outlined Empty Space for Big Sur is required and Apple has mentioned it very clearly.

Excerpt verbatim " f upgrading from macOS Sierra or later, macOS Big Sur requires 35.5GB of available storage to upgrade. If upgrading from an earlier release, macOS Big Sur requires up to 44.5GB of available storage. To upgrade from OS X Mountain Lion, first upgrade to OS X El Capitan, then upgrade to macOS Big Sur."

Now, if anyone has AntiVirus, Optimizers , Disk Cleanup etc installed - there will be many issues to be resolved before attempting the Upgrade

I am trying to install my MacBook Pro (13-inch, 2018, Four Thunderbolt 3 Ports) to Big Sur. I have downloaded the installer. When I run it, I can click through the Software Agreement, select my disk (Macintosh HD), then get to the progress bar that says "About 15 minute remaining".

About two minutes in, I get a a slide out dialog that says "An error occurred loading the update." Nothing else.

Space, the final frontier. It has run out of enough space. The fact only 29GB is purgeable, says it doesn't have the required 35 GB.

Backup your data to two external medium, and then remove the stuff that doesn't need to be on the hard disk all the time before installing.

I have the same problem and mu space available in my iMac is 2.1 TB with 42.87 GB purgeable, I have been trying more than 5 times, deleted the installer, and downloaded it again, still the same happen in13mins time. Anyone can help?

I have the same problem and mu space available in my iMac is 2.1 TB with 42.87 GB purgeable, I have been trying more than 5 times, deleted the installer, and downloaded it again, still the same happen in13mins time. What can I do?

I got the same error.

On my system there wasn't a space problem or a problem with the SSD.

I downloaded the full install package directly from Apple and that failed with the same error.

I created an USB installer with that direct download of Big Sur and the install failed with the same error.

I tried a clean install with the USB installer and the install failed with the same error.

I removed my WiFi networks from the MacBook and turned off WiFi. I then connected the MacBook to the

network via Ethernet using a ThunderBolt/Ethernet adapter.

I then retried the upgrade install using the USB installer and the Ethernet connection and success it completed the installation of Big Sur with no problems.

In your case - suggest shutdown by whatever means possible. Disconnect all external drives and connect to charger. Restart in Safe Mode - immediately at startup hold Shift key. It does a Repair Disk, clears cache files and only loads required Apple Software so . . it loads slowly - Normal. If it works, it may allow the installer of Big Sur to complete the installation and present the Setup Assist