Fi on a non-Google phone is like mowing your lawn with a weed eater….

Project Fi Logo

UPDATE: As of the 11/29/2019 Google Fi announcement, this article is pretty much old news but I’m leaving it here for reference. 


I’ve seen the “can you use Project Fi with an XYZ model phone” question over and over. Invariably someone (or several someones) will reply “yeah, it works”. And while this answer is kind of / sort of technically correct (with caveats), it’s misleading!  When I see this I imagine  quotes around the word works… it “works” – unfortunately, a lot of people take it at face value.


Before we go any further, you need to understand a couple of basic issues.  GSM carriers (like T-Mobile and AT&T) use sims to provision service on their network. The sim’s unique id is what is activated by the carrier and ties the service to whatever phone it’s inserted in. On the other hand, CDMA carriers (Sprint) only use the sim to provision the data portion of their service (LTE) – the cell side is provisioned based on a unique id in the PHONE. No other carrier automatically switches between GSM and CDMA, so, this means that Fi has to have low level access to the radios that most carriers don’t need and most manufacturers don’t currently support.

You also need to be aware that not all phones have all of the US cell bands that are used by T-Mobile and Sprint. For instance, the International versions of Nexus phones don’t have any CDMA bands.

About the Project Fi Sim and Unsupported Phones (I-Phone)

The Project Fi sim is reportedly different than other sims in that it has up to 10 virtual sims on the card.   This means that any phone you put it in will probably have to have a firmware update (at least) to utilize any of the virtual sims other than the first one (which is probably T-Mobile as that is how the sim will act when insert it in a non-Fi phone). Unfortunately, this means that the phone manufacturer (eg, Apple) would have to make changes to their phones before it would be able to fully support Project Fi (I honestly don’t see Apple ever doing that).

Activating your Project Fi Sim

The first thing that happens when you start the Project Fi activation process is that the Project Fi app verifies that you are using a supported phone. If you aren’t on a supported phone, the app stops the activation process. In short, you can NOT activate a Project Fi sim on an unsupported phone ( to me this means it does NOT work).

If you are on a supported phone, the app activates service on T-Mobile using the sim’s ID and then activates the PHONE’s unique ID on the Sprint Network.

So, I’ll just activate my sim in my friend’s Google Phone

And now we head down the rabbit hole.  Yes, you MAY be able to do that – BUT, you will be activating your friend’s phone on Sprint. This has a couple of possible side effects:

  • Your friends phone may have issues if he tries to activate Sprint service (either Sprint, Project Fi or any Sprint MVNO).
  • When you change out the sim, your phone will not be able to utilize the Sprint network. It will basically be a T-Mobile ONLY sim.

OK, so I’ll use a “Data Only Sim” Instead

Not so quick. The “Data Only Sim” is an ADD ON to a full sim, so if you can’t activate your primary sim, you won’t be able to use the data only one. This sim is intended as a way to get access to a SECOND device (like a tablet), not as your primary service.

Additional Things To Consider

  • Google will NOT support Project Fi on an unsupported phone.
  • Google has stated in the Network Policies section of their TOS that all “supported devices” will be listed on the Project Fi website and that they “reserve the right to suspend any device that we reasonably determine is unsupported”.  So, yes, they have the option of terminating your service for using a non-approved phone.


Basically, it’s like asking a group of guys “can I mow my lawn with a weed eater”?  There will be at least one guy that will says “sure, you can do that”. And while he is technically correct, and may be doing it himself; it is only kind of “working”.

Regardless of what you’ve heard – No, Project Fi sims do not work (note the lack of quotes) on unsupported phones! You probably need to consider a T-Mobile plan (or one of it’s MVNO’s – like Straight Talk).

Have fun and enjoy Project Fi!


9 thoughts on “Fi on a non-Google phone is like mowing your lawn with a weed eater….”

  1. What if your phone just broke and your trying to use your old moto x while you wait for the replacement?!?

  2. Not really, If you’ve done the math and looked at the map coverages to see that you rarely are a data hog or go into the boondocks of no service, using project fi (t-mobile only) on a unlocked non nexus phone is still as good as using it on a nexus phone.

    1. You’re right it “works”, it just doesn’t work with Sprint or US Cellular – it’s basically T-Mobile only. And you’ve probably locked the 5x off of Fi and Sprint.

      1. I’m using a OnePlus3 and I have a Nexus 5x. The 5x has not been blocked off of Fi. I switch between the two phones occasionally and quite frankly, the lack of Sprint or US Cellular doesn’t seem to be an issue because I have not run into any coverage issues using the One+ on Fi.

        1. By “locked off of Sprint”, I meant that the phone probably can’t be activated on Sprint for another user. You should be fine switching the activated Fi sim between phones. However if you sell the phone to a 3rd party, they probably wouldn’t be able to activate it on Sprint or any of the Sprint MVNO’s (like Project Fi).

  3. It feels like the biggest takeaway here is that there are implications for the Google phone that you use to activate Fi on — the “surrogate” phone. Otherwise, short of Google killing your Fi service, the only other gotcha is that the Fi app doesn’t work on your non-Google device. T-Mo coverage is fantastic!

    A lot of readers of this article likely are on the Google bandwagon already (they have a Nexus 6/5X/6P), and they want to explore other options. So tying up a surrogate phone isn’t a big deal.

    You get exactly the phone you want, on arguably the most reasonable plan out there, on arguably the least evil service provider. Where’s that great hacker satisfaction you get from cruising off the beaten path?

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