Fi Series 3+ review: our top pick for most dogs

Why it's our top pick

When your dog gets out, the best tracker is the one that's charged and on the dog. That's where the Fi pulls ahead. Fi says the Series 3+ lasts up to 3 months for a low-activity dog, 4 to 6 weeks for a moderately active one and up to 2 weeks for a very active one, with the included Fi Base at home. Halo and SpotOn want a charge about every day. Tractive's standard dog tracker lasts up to two weeks.

The reason is how the Fi connects. It always uses the lowest-power link it can find: the Fi Base first, then your phone, then your Wi-Fi, and only then GPS and the cellular network. At home it mostly rests. Once your dog is out, it reports by GPS and cellular, about every 5 minutes by default.

The tracker also sits inside the collar band itself, so there's no clip to snap off on a fence rail or in the brush. Collars come in five sizes, up to XL for dogs over 95 lb.

What happens when your dog gets out

You set Safe Zones around home and other places your dog spends time. When your dog leaves one without you, Fi sends an escape alert to your phone. Fi doesn't publish how fast that alert arrives. Dogster measured 2 to 12 minutes of lag on Safe Zone alerts in its testing, and we're timing it ourselves (see our results above). Fi says keeping your home Wi-Fi saved on the collar makes escape detection faster and more reliable.

Then you turn on Lost Dog Mode. The collar switches to real-time GPS updates every few seconds, so you can follow your dog on the map. You can turn on the collar's LED to spot them in the dark, and Fi's Search Party feature can alert other Fi users nearby. Lost Dog Mode is hard on the battery: Fi says it runs about 2 days in that mode, which is enough for a long search.

Battery: the claim and the catch

Fi's numbers assume the Fi Base is at home, and they shrink the more time your dog spends away from it. A dog on long daily hikes will land near the 2-week end. A couch-loving senior can stretch toward 3 months. The independent site Rebarkable measured 21.6 days from a full charge down to 10% in its September 2026 test.

To charge, you set the collar on the Fi Base, no cable needed, and a full charge takes about 3 hours. Some reviewers find the dock fiddly to line up. Our own battery numbers will land in the results box above.

What it costs

The Series 3+ collar is $129, and you need a membership to use the GPS tracking and escape alerts. Fi's prices, from its billing help page:

There's no monthly option, and every plan has a 6-month minimum. Plans renew on their own; Fi gives a full refund if you cancel within 30 days of a renewal charge. Year one comes to $318 ($129 collar plus the $189 one-year plan), and two years to $468 on the two-year plan. Shipping is free on orders over $100. Fi's billing page doesn't list an activation fee, but some reviewers have reported a $20 fee at checkout, so check your cart.

New customers can also try a Series 3+ through Fi's 30-day free trial. You pay $12 shipping, and it rolls into the $189 yearly plan unless you cancel and send it back. Read the trial terms first: returns are due within 14 days after the trial ends, and late or incomplete returns carry a fee. Our cost guide lines Fi up against every other tracker.

Coverage

The Series 3+ uses AT&T's LTE-M network, and Fi says your own phone doesn't need to be on AT&T. It works in the US, Canada and Mexico. LTE-M is a low-power network built for devices, and it can reach some places a regular phone signal doesn't, but rural gaps still exist. Fi's help center links carrier coverage maps; check the places your dog actually goes. Fi doesn't say whether the collar stores locations while it's out of coverage, and some owners report the map pin freezing until the collar reconnects. More on that in trackers without cell service.

Fit, build and the extras

The tracker weighs 47 grams and is rated IP68 for submersion plus IP66K against high-pressure water jets, so swims and hose-downs are fine. Beyond location, the Series 3+ tracks activity and sleep and watches for behaviors like barking, licking, scratching, eating and drinking. Fi is clear that this isn't a diagnosis. It also works with Apple Watch.

Where it falls short

• The membership adds up. At $189 a year ($169.50 a year on the two-year plan), Fi costs more to keep running than Tractive ($72–$144 a year) or Halo's Bronze plan (about $105–$110 a year).
• Escape alerts can lag. Reviewers and owners report delays and the occasional false alert. Saving your home Wi-Fi on the collar helps.
• Dogs only. For a cat or a very small dog, Fi points you to the lighter Fi Mini.
• Support and billing complaints. Fi held 3.3 out of 5 on Trustpilot in October 2026. Common gripes include billing and cancellations, slow support, GPS lag and battery drain.
• No satellite backup. In places with no cell signal at all, the Series 3+ can't report. Fi's newer Fi Ultra adds a satellite connection, at the cost of a 2–3 day battery.

Fi Series 3+ vs the alternatives

• Tractive DOG 6 costs less ($223 in year one) and adds heart and breathing-rate monitoring, but it clips onto your collar and needs a charge every week or two. Full comparison: Fi vs Tractive.
• Halo Collar 5 is the pick if you need to keep your dog inside a yard with no fence. It costs about twice as much and needs nightly charging.
• Fi Ultra adds a satellite connection through T-Mobile's T-Satellite with Starlink for places with no cell signal. It's $299, lasts 2–3 days per charge and works in the US only.
• Fi Mini is the $99 lightweight version for small dogs and cats. For cats, see GPS trackers for cats.

Questions people ask