Take a few easy steps to verify that the file you downloaded is the file you wanted Having a Nexus means you're provided with factory restore images should you want to revert anything you might have done to the system software. It's a failsafe, and the easiest way to return everything to the way it's "supposed" to be. More than a few people with Nexus phones use them — both for their intended purpose and as a way to get an update without waiting. What we need to remember is that means one more thing that can (and eventually will) go wrong. You're downloading a large and intricate set of bits and bytes. You should take a few minutes and verify the bits and bytes you downloaded are an exact copy of the bits and bytes that were uploaded. The easiest way to do this is to verify the file checksum.

What is a file checksum?

Simply put, it's a digital signature for the file. If the copy you have (the one you downloaded) has the same signature as is provided by the people hosting the file (in this case, Google) you have an exact copy of the file. Verizon is offering the Pixel 4a for just $10/mo on new Unlimited lines Google provides both the MD5 checksum and the SHA-1 checksum for Nexus factory images. It's worth noting that neither of these signatures is 100 percent "secure" — they can be manipulated after the fact by people wth plenty of time and dedication. If you're in need of a way to verify something important that more than one person had access to before it landed in your hands, use a stronger algorithm. But to verify a download that you downloaded directly, either MD5 or SHA-1 is more than sufficient. Why use a checksum at all?