I'm using the Firebase Emulator to run all Firebase services. I have managed to run the emulator with a backup of my Firestore data by running:
firebase emulators:start --import ./my-directory
... but I can't find a way to do the same with my Storage data.
Firestore has an option to do import and export, while Firebase storage don't have this feature yet (storage uses upload and download). Currently, there's no native way to import Google Cloud Storage data in the Storage Emulator.
Additionally, you can study how the emulator register the object by uploading sample files within the emulator and then running the export, you will see that the emulator will require 1 object and 1 JSON file that contains it's metadata. For now, it'll be up to you to download the objects from your production bucket along with a separate JSON file containing its metadata and then structure it for import.
There's also an opened issue for this in github that you can monitor as well.
Although @RJC's answer is correct, I want to share what I did.
You can add the option --export-on-exit when starting the emulator, and it will export the state of the local Firebase instance to a folder of your choice. So I downloaded all my data from the real Firebase project, uploaded everything with the Emulator, then killed the emulator, everything (including storage) got exported and now I start it with the --import option using the same folder where I exported everything.
This was not very awful since I didn't that much stuff in my storage.
