Testing out the COROS APEX 4 for the past couple of weeks has given me flashbacks to wearing the 2022 Garmin Forerunner 955, my favorite running watch before Garmin and its rivals began shifting away from MIP displays. Plenty of fitness watch fans detest this trend, like my 955-wearing brother-in-law. While I’ll admit I prefer AMOLED displays, the APEX 4 is a great watch for the holdouts.
COROS’s last watch, the NOMAD, challenges the Garmin Instinct 3 in a narrow category: affordable, rugged hiking watches with weeks of battery life. An MIP display felt like the right fit.
The APEX 4 targets trail runners and “mountain athletes” who also care about battery life and outdoor visibility. But its $429/479 price gives it stiffer competition from the Suunto Race 2, Garmin Forerunner 570, and Polar Vantage M3 — all AMOLED watches, and the first two with 2,000 nits for excellent readability in direct sunlight.
Initial thoughts
I reviewed the COROS APEX 2 and APEX 2 Pro in 2022 when I was still relatively new to wearables. The hardware impressed me, especially the epic battery life, but I could tell that the GPS and HR accuracy could be better, the health tracking and software had plenty of gaps, and the MIP displays were painfully dim.
Unsurprisingly, the APEX 4 is more reliably accurate (as you’ll see below), the battery life still blows me away, and the MIP display has much better contrast, making it serviceable — though for whatever reason, the NOMAD’s display is more readable indoors. I think the APEX 4’s sapphire layer catches more obscuring light.
Most importantly, the APEX 4’s new Ambiq Apollo 510 processor powers the speediest, smoothest maps I’ve seen outside of Apple and Wear OS watches, where most fitness watch rivals like Garmin are laggy. You now get street and trail names, and the crown makes it seamless to zoom in to a confusing trail turn or out to a wider view in a couple of seconds.
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My only complaints are with the turn-by-turn navigation for downloaded courses. It mostly works without issue, but I noticed twice that when I came to a loop, the arrow suggested I go in the opposite direction that I chose when I made the course.
When I intentionally went off course, the APEX 4 caught it and warned me immediately. But the turn-by-turn directions don’t update based on which direction you’re facing, so when I missed my right turn and turned around, it still told me to turn right. I hope COROS can address both of my map nitpicks in the future.
With its new processor, the APEX 4 is primed for years of upgrades. Over three years, the APEX 2 added HRV and stress data, sleep quality, and running form analysis, Strava Live Segments, and safety alerts, among dozens of new features. While Garmin watch updates tend to dry up after 1–2 years, APEX 4 updates should last much longer.
I specifically expect its built-in depth gauge sensor to enable scuba diving at some point, and COROS told Chase the Summit that it may use the mic & speaker to enable offline voice commands in the future.
COROS APEX 4 GPS accuracy
Not all dual-band GPS watches are created equal. Having tested nearly every smartwatch brand’s GPS accuracy, I’ve found that COROS’s most recent watches come the closest to Garmin for dependability, with the APEX 4 following that pattern. Get ready for some boringly straight GPS lines, with only a couple of glitches to speak of.
I took three dual-frequency GPS watches — the Garmin Forerunner 970, Google Pixel Watch 4, and APEX 4 — out for a 19-mile run; while Google depends mainly on L1 and L5 GPS frequencies, Garmin and COROS also pull in other GNSS signals as needed.
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By the end, Garmin measured 0.01 miles more and Google 0.01 miles less; you can read my Pixel Watch 4 fitness test if you want to see its results, but I’ve focused on the two main rivals here. By and large, all nineteen miles showed the two signals either overlapping or in close parallel with each other. They tended to ding simultaneously or within seconds at each mile marker.
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I only have one complaint: The APEX 4’s final map showed me warping from my current spot to a previous one, then back, as seen above. It didn’t affect my distance results, but it did add about 50m to my final altitude totals. I noticed a similar glitch hiking with the NOMAD in August, adding 170m of extra ascent but no extra distance.
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For a second 8-mile run, thankfully, we’re right back to superbly, dully accurate GPS data from both the APEX 4 and Forerunner 970, their GPS lines overlapping or paralleling one another for almost the entire run. I’ve also noticed that the APEX 4 tends to do slightly better with tunnels and underpasses, staying straight while Garmin’s line waves slightly.
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During a 5-mile hike, neither watch was perfect, each having moments where they strayed slightly from the satellite trail path. Both ended with the same 5.44-mile distance, while my Suunto Race 2 measured 5.43 miles.
What’s odd is that COROS measured about 100 feet of extra elevation gain (1,762 feet) compared to Garmin (1,660 feet) and Suunto (1,644 feet). I’m not sure what to make of two activities with excess ascent totals, so I’ll keep testing it in my full APEX 4 review.
COROS APEX 4 HR accuracy
I’ve generally found COROS watches’ HR accuracy to be reliable, but not perfect, especially for the highest anaerobic data. I don’t mind because the COROS HRM is affordable and comfortable to improve your data, and most COROS watches are cheap, but you’d want the pricier APEX 4 to stand on its own merits.
This graph shows how the COROS APEX 4 and Garmin Forerunner 970 optical HR sensors compare. COROS and Garmin’s HR averages ended 1 bpm apart, but you can see how the two watches react to my changes in effort equally fast and generally mirror one another; the only difference is that COROS’s results were barely higher.
A more reliable accuracy test came during my 19-mile run, during which I wore a Garmin HRM 200 chest strap as a control group. The COROS APEX 4 ended with the same 161 bpm average and 178 bpm maximum rate.
You can certainly see points in the graph where the two diverge as I climbed into higher heart rates. The APEX 4 trails behind the chest strap to hit higher HRs, then stays high while the chest strap measures my effort level decreasing.
The photo above, with the Forerunner synced to my chest strap, shows how you might not immediately see how hard you’re pushing with the APEX 4 at any given moment. So if you used the APEX 4 for an anaerobic track workout, I’d expect the HR average would fall a couple of bpm short. This is common for wrist-based optical sensors, but keep that in mind.
Wrist-based optical sensors can also struggle with sustained, lower HR levels, but the COROS APEX 4 matched the Garmin HRM 200 chest strap for HR average and maximum during my two-hour hike. It’s closely aligned 90% of the time, with the APEX 4 doing very well at catching when my HR rose on tough hills. But there were a few moments where my effort dipped but the APEX 4 stayed 5–10 bpm above my HR.
Is the COROS APEX 4 the right watch for you?
COROS reps said during our APEX 4 briefing that they “will still have a split of AMOLED and MIP watches in the future,” but that they “still find MIP to be a phenomenal solution.” The only current COROS AMOLED is the excellent COROS PACE Pro, but I don’t think there will be an APEX 4 Pro with AMOLED anytime soon.
Without wading into the MIP vs. AMOLED debate, the APEX 4 is the right fit for people who prioritize outdoor visibility and longer battery life. I’d argue the latest 2,000-nit Garmin watches are perfectly visible outdoors, but their battery life does suffer for the extra brightness, while the APEX 4 has that classic longevity, to the point that I still haven’t charged it since I unboxed it.
The APEX 4 reminds me of premium fitness watches from three years ago, when there was less industry pressure to add “smarts” like you’d find on an Apple or Galaxy Watch. The UI revolves solely around fitness: What’s next on your marathon training plan, how much training load, have you built up, and how does your HRV, stress, and sleep play into your recovery?
But I’m less tolerant of certain things in 2025 than I was in 2022, like how the basic COROS UI crams dozens of tools into an annoying, rotating Toolbox, or the overly-large “COROS” label next to the display that detracts from its premium look.
Picking or skipping the APEX 4 comes down to your priorities as an athlete. Switching to the Forerunner 570, for example, would net you a flashlight, daily run suggestions, better music apps, contactless payments, and (arguably) a better display, but would lose you sapphire glass, a more stylish steel bezel, offline maps, and 5–11 days of battery life.
The APEX 4 is what grumbling Garmin users say that they want: A return to the MIP days, where they focused on fitness essentials and battery life over expensive bells and whistles, with a reasonable price and no frustrating feature-locking of the best features like maps.
I’ll have a full review coming soon with more feature testing, but it’s undoubtedly one of the best running watches of 2025…if you don’t prefer AMOLED.
The COROS APEX 4 offers a 1.3-inch AMOLED touch display with sapphire glass, 41 hours of dual-band GPS with a 24-day battery life overall, 32GB of storage for music, maps, and routes, and a mic & speaker for Bluetooth calls and Voice Pin diary entries during your hikes, which are then saved to your activities to share with friends. It’s built for serious outdoor athletes.