Gab is older and in the old days, attracted alt right and downright nazis, however they banned the absolute worst by now.
So it has roots in the alt-right/nazi/4chan community and predates parler by a lot.
They used to have their own software, then switched to mastodon, but turned off the peering and added custom code apparently full of SQL injection.
Parler is very new and has roots in more conservative circles. It’s written from ground up and is apparently pretty bad, although it’s not working anymore.
So it has roots in the alt-right/nazi/4chan community and predates parler by a lot.
They used to have their own software, then switched to mastodon, but turned off the peering and added custom code apparently full of SQL injection.
Parler is very new and has roots in more conservative circles. It’s written from ground up and is apparently pretty bad, although it’s not working anymore.