New Samsung Galaxy Watch4 Update: What is New and Why You Should Upgrade?

By Saroj Yadav — Founder, TechXomos  |  Published: January 1, 2026  |  Updated: March 2026
Sources: Samsung Official Security Bulletin, SamMobile, Galaxy Store Community, In-House Testing

Galaxy Watch4 was released in 2021. The watch itself was already aging in one particular direction by the time One UI 8 came; battery life had silently dropped down to between 18 and 22 hours with moderate use, which is significantly less than the approximate 40 hours that Samsung was initially promising. This is directly addressed in the JYL6 update that is currently being rolled out to Watch4 and Watch4 Classic owners across the globe. It also fixes two other issues that frustrated users for months: erratic Always-On Display behaviour and occasional heart rate sensor freezes during workout sessions.

This is not a feature update. Samsung is not adding anything new to a five-year-old watch. What JYL6 does is stabilise the software stack — roll back aggressive background process management that was introduced in an earlier One UI 8 patch and inadvertently broke battery performance, restore reliable AOD wake timing, and include the January 2026 Android security patch for wearable devices. That last part matters for people who use the watch's ECG and blood pressure monitoring features, since these transmit health data that deserves up-to-date protection.

We ran the update on a Galaxy Watch4 LTE unit for 48 hours before writing this. The honest short version: battery improvement is real and measurable. The AOD fix works. The health sensor behaviour is noticeably more consistent. Whether it is worth the 10-minute install process — it is.

Samsung Galaxy Watch4 — the JYL6 update is rolling out globally as of January 2026. (Source: Samsung)

What Broke Before JYL6 — And Why

Understanding what JYL6 fixes requires a quick look at what went wrong before it. The Watch4 uses Wear OS 3.5 and has a top layer of Samsung One UI Watch. With the release of the One UI 8 update, the background process controls became even stricter, with this being a modification that would help to increase the battery life of newer Galaxy Watch6 and Watch7 models. The issue is that such controls were not properly adjusted to the older Exynos W920 chip of Watch4 which has a different approach to memory management.

The result was the opposite of the intended outcome. The Watch4 ended up doing more computational work to compensate for the aggressive process kills, which drained the battery faster. Reports in the Samsung Community forums from November and December 2025 described battery life dropping from a full day to under 18 hours on standard use — exactly the scenario JYL6 is designed to correct by reverting and recalibrating those process management parameters for the W920 hardware specifically.

The AOD issue was separate. A display timing bug caused the always-on display to wake at incorrect intervals, which kept the screen active longer than intended — again burning battery, and also creating an odd experience where the display would light up mid-pocket. That specific bug is patched in JYL6.

JYL6 Update — Version Details and Rollout Status

JYL6 firmware version details screen on Galaxy Watch4. The update includes the January 2026 Android security patch for wearable devices.

The version of firmware that appears as JYL6 is applicable to both the regular Galaxy Watch4 and the Galaxy Watch4 Classic that includes Bluetooth and LTE models. Samung began its launch in Europe and South Korea initially, and India and Southeast Asia on the same week. In the middle of January 2026, SamMobile stated that the update was widely distributed in leading markets.

Unless the update has already shown up on your watch, the surest method of checking is via the Galaxy Wearable app on your phone instead of waiting to receive an over-the -air notification. Enter Watch Settings Watch Software Update Check for updates. It is about 85MB in download size and therefore a Wi-Fi connection is advised before commencement.

Our 48-Hour Testing Results — What Actually Changed

Battery life: The most noticeable change. Before JYL6, our Watch4 test unit was ending the day at roughly 28–32% battery with the usage pattern described above. After the update, the same usage pattern left us at 47–51% at the end of day one. That is a real-world improvement of roughly 18–20 percentage points — consistent with what the community has been reporting across the Samsung forums and Reddit's r/GalaxyWatch.

AOD behaviour: Fixed. The erratic mid-pocket wakeups are gone in our testing. The AOD now follows the set schedule reliably. This alone likely accounts for 10–15% of the battery improvement.

Heart rate during exercise: We ran two 30-minute outdoor sessions after the update. Heart rate data was continuous and consistent throughout both runs — no dropouts or frozen readings. Before the update, the same conditions typically produced 2–4 missed readings per session in our experience. Post-update: zero dropouts across both test runs.

Sleep tracking: Sleep stage detection felt more accurate — specifically, the transition between Light and REM sleep stages was flagged more consistently with our subjective sleep experience. This is harder to verify objectively without medical-grade equipment, so treat this as an observation rather than a confirmed finding.

One genuine caveat: Right after the initial install, we noticed minor notification delivery delays — roughly 5–10 seconds before a phone notification showed up on the watch. This cleared up after a restart. If you experience it, a quick restart of both the watch and the paired phone resolves it in most cases.

Before vs After JYL6 — Key Metrics Compared

Testing conducted on Galaxy Watch4 LTE 44mm over 48 hours. Results may vary based on usage patterns and paired device.

Health and Fitness Tracking — What Changed and What Didn't

The Galaxy Watch4's BioActive sensor — JYL6 recalibrates heart rate and sleep detection logic. Image: Samsung.

The JYL6 update includes recalibrations to two specific health monitoring functions — heart rate detection and sleep stage analysis. These are software-level adjustments to the BioActive sensor's processing logic, not hardware changes.

Heart rate: The fix targets missed readings during high-intensity intervals specifically — situations where rapid movement causes optical sensor interference. Samsung adjusted the fallback algorithm that engages when the primary reading confidence drops below a threshold. In plain terms: the watch now holds onto a reading slightly longer before calling it a miss, which reduces gap events during workouts without compromising accuracy on the upside.

Sleep tracking: The REM detection logic has been updated. Earlier builds of One UI 8 Watch tended to under-report REM sleep — a known community complaint since late 2025. JYL6 adjusts the thresholds that classify movement and heart rate variability patterns as REM activity. Whether this makes the Watch4 more accurate is genuinely hard to verify at home, but the reported sleep stage durations are now more consistent with user expectations based on subjective sleep quality.

What did not change: Body Composition (BIA) measurement, blood oxygen SpO2 monitoring, ECG functionality, and stress tracking are unchanged in this update. JYL6 is a stability and security patch — it does not add or significantly alter features beyond the recalibrations noted above.

How to Install the JYL6 Update — Step-by-Step

The installation is straightforward. The whole process takes about 10 minutes including download time on a decent Wi-Fi connection.

1. Check battery first: Make sure the watch is at 50% or above. The update will not begin below this threshold — Samsung enforces it automatically.
2. Connect to Wi-Fi: The update downloads on the watch directly. Use a stable 2.4GHz or 5GHz network. Mobile data is not used for watch firmware downloads.
3. Open Galaxy Wearable: On your paired Android phone, open the Galaxy Wearable app.
4. Navigate to Watch Software Update: Tap your watch name → Watch Settings → Watch Software Update → tap Download and Install.
5. Wait and let it complete: Do not press any buttons on the watch during the install. The watch will reboot automatically.
6. Restart both devices: After the watch reboots, restart your paired phone as well. This clears any temporary pairing cache and resolves the notification delay issue most users experience immediately post-update.

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