Looking at the sources in /etc/apt for the 32-bit release of Raspberry Pi OS one findsNo. It isn't.Are you kidding? That's the stand OS used on Raspberries.
The standard OS is Raspberry Pi OS. Raspbian is and always has been a third party OS.
https://legacy.raspbian.org/
or
http://raspbian.raspberrypi.org/
depending on the release.
My understanding is the Zero and original Pi A, B and B+ are based on an ARMv6 processor with hardware float--also called arm1176jzf-s. At the time Debian included repositories for ARMv6 but no hardware float. Since software float is very slow, the Debian packages were rebuilt with the necessary options to enable hardware float and the resulting repository called Raspbian.
Note the people who rebuilt the packages did not work for Raspberry Pi.
After some time it was decided that the additional customisations performed by Raspberry Pi to make an image were significant enough to warrant a separate name. The last I heard Raspbian was downstream from Debian and 32-bit Raspberry Pi OS directly used the binary packages from the Raspbian repository.
The situation is somewhat different for 64-bit Raspberry Pi OS since there is no need to rebuild the Debian packages to take advantage of the ARMv8 processors used in the Pi 3, 4 and 5.
My impression is the third party which historically built the Raspbian repository used by Raspberry Pi OS is finding it more and more difficult to build ARMv6 compatible packages. It'd be interesting to know if the arrangement described above is still accurate for Trixie. If anyone knows, please reply.
On the other hand, the focus of this thread is not the distinction between Raspberry Pi OS and the Raspbian repository, but how to format an SD card using Raspberry Pi Imager.
Unfortunately, that's a more difficult problem to solve. More information is at
viewtopic.php?t=395443
and other threads on this forum.
Statistics: Posted by ejolson — Sun Jan 18, 2026 2:55 am