| 52 || all Extensions marked "multiprocessCompatible" and all WebExtensions [1]
|-
| 53 || all Extensions marked "multiprocessCompatible" and all WebExtensions [1]. Beta testing on add-ons that don't use compatibility shims (~400 based on telemetry)
|-
| 54 || all Extensions marked "multiprocessCompatible" and all WebExtensions [1]. Possibly add-ons that don't use compatibility shims.
|-
| 55 || all Extensions marked "multiprocessCompatible" and all WebExtensions [1]. Possibly add-ons that don't use compatibility shims.
|-
| 56 || all Extensions marked "multiprocessCompatible" and all WebExtensions [1]. Possibly add-ons that don't use compatibility shims.
|-
| 57 || ONLY webextensions supported [4]