According to Huawei, a developer could build an experience using HarmonyOS for one product category and the platform would then be able to adapt said experience to work across other types of products with minimal effort.
Which devices support HarmonyOS?
At present HarmonyOS remains in beta, with version 2.0 offering smartphone compatibility for the first time. Version 1.0 was first seen running on the company's own smart TVs and its AX3 WiFi router.
Huawei's device adaptation roadmap for HarmonyOS 2.0 details:
From 10 September 2020 – Devices with 128KB to 128MB RAM
From 21 April 2021 – Devices with 128MB to 4GB RAM
From October 2021 – Devices with 4GB or more of RAM
The company hopes to have HarmonyOS 2.0 running on over 200 million devices by the end of 2021; a figure made up of, not only Huawei's own products but those made by its partners too.
Is HarmonyOS replacing Android on Huawei phones?
Yes and no... Huawei's own documentation and marketing surrounding HarmonyOS suggest that it serves as a complete end-to-end replacement for Android on its smartphones and tablets.
However, ArsTechnica conducted an in-depth review of the HarmonyOS 2.0 beta, along with its development tools, and concluded that, in its current state, HarmonyOS 2.0 was essentially Android (version 10) in all but name.
Some fundamental components of HarmonyOS 2.0 still make reference to Android, which the company has used to power its smartphones since they first hit the market.
While HarmonyOS' official marketing and development paperwork appear to be intentionally written to obfuscate the fact this it is essentially a forked version of Android, it does appear to be based on Google's mobile OS, so to say that it is replacing Android on the company's smartphones isn't exactly correct.
When will we see HarmonyOS on a smartphone?
The smartphone-compatible HarmonyOS 2.0 beta went live in December 2020 but the company confirmed at the unveiling of its latest foldable, the Mate X2, in China on 22 February 2021, that “flagship phone users will be able to upgrade their phones to HarmonyOS starting from this April,” with the X2 being the first smartphone to run HarmonyOS.
This appears to be in conflict with the roadmap it laid out previously, which could suggest an accelerated adoption of the platform on devices with more memory sooner than expected. It's unclear how HarmonyOS' rollout will differ between Huawei's native market of China and for users and devices in other regions where it operates.