how to keep only 11 length by line in notepad?

for exemple, there will be a list like this one:

12345678901:1020
12345678902:1030563

I'd like to keep it like this format:

12345678901
12345678902

basically, 11 digits by line

You may do the following find and replace, in regex mode:

Find:    ^(.{1,11}).*$
Replace: $1

Demo