ALL THINGS YOU NEED TO KNOW ABOUT PROJECT FI..

WHAT IS PROJECT FI?

At the highest level, Project Fi is a prepaid phone carrier offering from Google. It works by giving you mobile data service on two mobile networks, which your phone will intelligently switch between — it also uses Wifi to make calls and send texts whenever available. Project Fi is a "prepaid" carrier, meaning you pay up front for your service in the trailing month, which is the opposite of a traditional carrier that bills you after you use the service.
Fi is focused on simplified billing. You pay $20 per month for unlimited talk and texting, and a flat rate of $10 per gigabyte of data used. At the start of each month you simply estimate how much data you'll use and pay for that amount — at the end of the month you'll receive either a refund for data you didn't use, or pay a little extra on the next bill for data overages. You'll always pay at the same $10 per gigabyte rate, though, no matter what.

HOW DOES IT WORK?

Project Fi works with a special SIM card — and a little software on your phone — that can authenticate you on both T-Mobile and Sprint, and switch between them on the fly based on a variety of factors. Because it can also use Wifi for calls and texts, you can keep using your phone in places where mobile data isn't that great. Extra software called a "Wifi Assistant" will automatically connect your phone to open Wifi access points when you're out of the house, reducing your data usage without any intervention on your part.
When you use Project Fi, you also get some of the same features that have made Google Voicepopular over the years. You can forward phone calls to your Fi number to any phone you want, as well as view voicemail, make calls and send texts with that number from any device using the Hangouts app.
Project Fi also works internationally in 120 countries around the world with no additional cost for data use or texting. You can call at a flat rate to any number while on the cellular networks abroad, or pay much lower rates when calling on Wifi. You can also call back home to the U.S. on Wifi for free. Data used internationally just comes out of your standard $10 per gigabyte bucket, but speeds are limited to 256kbps (double what T-Mobile offers outside of North America).

WHY DO I WANT IT?

The first limitation is phone choice. Google lets you choose from one of its latest three Nexus phones — the Nexus 6P, Nexus 5X or Nexus 6 — but those are the only three phones you can use with the service right now. You can request an invite to be part of Project Fi, and when you're selected you'll have either a SIM card for your existing Nexus shipped out or you can buy a new phone right from Google, including with 24 month financing. You can use it for as long or short as you like, and there's no activation fee or service commitment.

There are lots of cool features that make Project Fi a good choice, like the simplified billing, included international features and improved network coverage through the use of two carriers and Wifi networks. Each one will have a different amount of draw for different people, though.

Project Fi's pricing isn't dramatically lower than other carriers out there, and whether it makes a good choice financially for you depends on your data usage and which features you want. We encourage you to do your pricing research before choosing which carrier is the best.