Nitecore NU25 UL Review
The Nitecore NU25 UL packs 400 lumens, dual-beam optics, IP66 weatherproofing, and USB-C charging into a 45g headlamp that's become the de facto standard for ultralight hikers.
Overview
The Nitecore NU25 UL is a dual-beam, USB-C rechargeable headlamp that has carved out a well-earned reputation as the go-to light for weight-conscious hikers and thru-packers. Weighing in at an astonishingly low 1.6 oz, it’s one of the lightest headlamps available, making it ideal for ultralight-focused activities like trail running, long-distance hiking, and alpine climbing. For the price — typically around $37 — the feature set is genuinely hard to argue with.
Heads up: Nitecore has since released the NU25 MCT UL (March 2025), which adds multi-color temperature LEDs and a slightly larger battery. The second-gen NU25 UL reviewed here has been discontinued. The core design and weight class remain the same, so this review still has legs if you’re sourcing one secondhand or evaluating the platform.
Key Specs
| Spec | Value |
|---|---|
| Weight | 45 g (1.59 oz) |
| Dimensions | 60.1 × 33 × 25.5 mm |
| Max Output | 400 lumens |
| Max Beam Distance | 64 m |
| Max Beam Intensity | 1,029 cd |
| Max Runtime | 45 hours (ultralow) |
| Battery | Built-in 650 mAh Li-ion |
| Charging | USB-C (~1.5 hrs to full) |
| IP Rating | IP66 |
| Impact Resistance | 1 m |
| Special Modes | Red Light, Location Beacon, SOS |
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Light Output & Beam Quality
The NU25 UL offers both spot and flood lights that can be used separately or together, letting you tailor the output to your specific activity.
One LED is coupled to a floody TIR optic while the other is designed more for throw — so you not only have multiple output levels, you can have three different beam profiles, using either LED or both together.
That’s a lot of flexibility in a 45 g package.
Measured with an Opple light meter, the dual white LEDs land at a CCT of around 5,409K and an Ra of 70.2.
The color rendering index won’t impress photographers, but it’s serviceable for everything trail-related.
None of the light modes, even on the highest setting, felt too harsh, and the blend of spot and floodlights was excellent for nighttime activities such as climbing, trail running, hiking, and camping.
In real-world testing, the headlamp can throw a beam roughly 70 yards — impressive for the weight class.
One legitimate gripe: the red light mode is the main downside. In some situations, like entering a tent with sleeping campmates, the red light felt too bright, and there’s no option to dim it or switch to a single red LED.
Battery Life & Charging
Claimed burn times proved accurate and comparable to the Black Diamond Spot series and the Petzl Actik CORE. In high mode, expect around 2 hours 40 minutes; in low mode, roughly 10 hours 25 minutes.
In ultralow mode, Nitecore claims an impressive 45 hours, which could be incredibly useful for thru-hiking or emergency situations.
USB-C charging is a genuine win — the NU25 UL recharges from 0 to 100% in under an hour and a half.
The 650 mAh internal battery can fully recharge in about 1 hour in practice, though Nitecore’s official spec states 1.5 hours.
Either way, a quick top-up from a small power bank before bed covers most multi-day itineraries without any battery-swapping anxiety.
The non-replaceable battery is worth naming directly: in the unlikely event of battery failure, you probably can’t restore the headlamp to working order — but Li-ion batteries rarely fail, and the weight savings from the integrated design are real. It’s a reasonable trade-off for the ultralight crowd.
Strap & Fit
The UL headband is a dual-cord system that distributes weight, glows in the dark, and features silicone for enhanced grip.
It looks spindly on the shelf. On your head, it earns its place.
The weight savings largely come from this slim shock cord-style strap which, despite looking too minimal to hold the lamp securely during high-output activities, works exactly as intended — surprisingly reliable and comfortable even during intense movement.
The NU25 UL rates fairly high on the comfort scale overall, and the foam backing makes it wearable for several hours at a time.
If you’ve ever worn swim goggles, the cord strap will feel instantly familiar. If you prefer the wrapped, padded feel of a traditional headband, note that the standard NU25 (same electronics, different strap) offers that at a small weight penalty.
Durability & Weatherproofing
The IP66 rating means the NU25 can stand up to rain and dust, but it won’t handle being fully submerged in water.
That’s enough for any reasonable trail condition.
In one real-world test, the headlamp was taken down to 22°F and woke up covered in condensation — and worked perfectly through that abuse.
Controls & UI
The NU25 UL uses a two-button design. The larger main button turns the headlamp on and off; quick taps cycle through high, medium, and low. A double-tap while off activates ultralow. The smaller mode button toggles between spot, flood, combined, and red light. Double-tapping mode activates strobe, and holding both buttons enables the lockout function.
That’s a lot of functionality compressed into two buttons. There is some trade-off in terms of a fairly complex and confusing user interface. It takes a few sessions in camp to internalize — reading the manual before your first trip out is genuinely recommended here.
Pros & Cons
Pros
- Exceptional weight-to-output ratio at 45 g / 400 lumens
- Dual-beam (spot + flood, independently or combined) adds real versatility
- Accurate manufacturer runtime claims; 45-hour ultralow is trip-proof
- USB-C charges in under 1.5 hours — fast top-ups from any power bank
- IP66 weatherproofing handles all practical trail conditions
- 4-LED battery indicator removes guesswork before departure
- Glow-in-the-dark, reflective cord strap is more comfortable than it looks
- Lockout mode prevents bag-drain
- Strong value at ~$37
Cons
- Red light has no dim setting — too bright for low-impact situations like sharing a tent
- Non-replaceable battery is a long-term durability concern
- Two-button UI has a learning curve; modes require a manual read
- Cord strap won’t suit everyone; traditional-band users should consider the standard NU25
- 650 mAh capacity is modest — multi-week thru-hikers will need power bank top-ups
- Now discontinued; the NU25 MCT UL supersedes it
Who Should Buy This
The NU25 UL is the right call for thru-hikers, long-distance trail runners, and gram-conscious backpackers who want a dependable, weatherproof headlamp without dedicating a meaningful slice of their base weight to lighting. It’s equally at home as a primary light on a JMT trip or as an ultralight backup on a ski tour. The broad consensus among ultralight backpackers and thru-hikers is that this headlamp is best in class — and the price makes it easy to keep a spare. If you’re a heavy night-hiker who needs 600+ lumens routinely, step up to the NU27 or a similar high-output model. Everyone else is well-served here.
Verdict
The Nitecore NU25 UL does the hard thing well: it makes almost no weight compromises visible on trail. You get genuine 400-lumen output, a real IP rating, USB-C charging, and a surprisingly capable dual-beam optic in a package that barely registers on your head. The red light limitation and the modal UI are real friction points, but neither is a dealbreaker in the field. At its price point, it remains one of the most defensible headlamp choices in the ultralight space — even as the newer MCT UL takes over the catalog.
Rating: 8.5 / 10