The domain of one blog is like its online ID.
Changing it could be a big step, and also create a mess, depending on the situation.
There are 3 types of domain change:
- blogspot to a custom domain
- custom domain to a custom domain
- blogspot to a blogspot
The first scenario is easily handled by Blogger, we just need to connect the domain correctly.
On the second one, we will need to follow some steps:
- Remove the custom domain from Blogger, on Settings.
- Add the new one, then go to your domain provider and set up the connection.
- For the old one, go to the domain provider and set up a 301 redirection, path to path.
- On Search Console, add the new domain as property.
- Uses the Change of Address tool.
But the last scenario is the worst of them.
Blogspot URLs can not be redirected, so any post or page previously shared will show this message:
People could use the Redirect tool of Blogger, but this is not a good practice and could be seen as violating the Content Policy.
What I recommend is to create a new blog with the old URL, and there put a big message about the new 'site'.
In one thread on the Blogger Help Community, I even shared a simple but effective theme that could be used to display the message: Static theme for Blogger.
As you could see, each case needs different aproach.
If you feel you will need help, just contact me and gladfully I will work with you.