Straight from Codex:
When your domain name or URLs change there are additional concerns.
The files and database can be moved, however references to the old
domain name or location will remain in the database, and that can
cause issues with links or theme display.If you do a search and replace on your entire database to change the
URLs, you can cause issues with data serialization, due to the fact
that some themes and widgets store values with the length of your URL
marked. When this changes, things break. To avoid that serialization
issue, you have four options:
- Use the Velvet Blues Update URLs plugin if you can access your WP
Admin Dashboard.- Use the Better Search Replace plugin if you can access your WP Admin Dashboard.
- Use WP-CLI’s search-replace if your hosting provider (or you) have installed WP-CLI.
- Use the Search and Replace for WordPress Databases Script to safely change all instances
on your old domain or path to your new one. (** only use this option
if you are comfortable with database administration ** )