Carbon Copy Cloner is an essential Mac app from Bombich Software Inc. that offers reliable backup, restore, cloning and integrity-checking capabilities for the Mac. Features include bootable backup clones, network and disk image support, incremental backups (with optional archiving), scheduling, built-in help/guidance, graceful handling of I/O errors, task history, editing of scheduled tasks, task-chaining for creating more complicated backup schemes, the ability to add a Recovery partition and much more. Version 5 brought APFS support for macOS 10.13 High Sierra and later, along with improvements to SafetyNet, scheduling, task management, restore and more.
The latest release works around a nasty problem with Apple’s recent macOS 10.15.5 update, among other changes. (See also macOS Catalina Known Issues and the excellent troubleshooting tips in “Help! My clone won’t boot!“.)
A bug in macOS 10.15.5 impacts bootable backups, but we’ve got you covered
Update (May 29, 2020): This issue is now addressed in CCC 5.1.18, which is available for immediate download.
… I suppose we’ll find out in future OS releases whether this was a simple filesystem bug that slipped into a production OS release, or if Apple finds it to be an acceptable practice to blindside developers by silently removing documented functionality in the middle of a production OS release cycle.