The idea is to list the local branches using git branch, filter the results and apply git branch -d for each line.

Linux/MacOS

git branch | grep -v master | xargs git branch -d

git branch lists all available local branches. With grep -v the master branch is filtered out. Then each line is passed to git branch -D using xargs.

Windows

FOR /f "tokens=*" %%G IN ('git branch ^| findstr /v master') DO git branch -d %%G

The same idea here, but with different tools. Instead of grep -v we’ll use findstr /v. Unfortunately xargs has no alternative, the only way is to use a for loop.

PowerShell

git branch --format '%(refname:lstrip=2)' | Where-Object { $_ -ne 'master' } | ForEach-Object { git branch -d $_ }

Here we output the branches without leading spaces and in quotes(--format '%(refname:lstrip=2)'). The grep -v alternative in PowerShell is Where-Object with the -ne (not equals) operator. Then for each line git branch -d is applied with ForEach-Object, which is the xargs alternative.