Our verdict

The On Cloudspark is uniquely crafted with women in mind from the start, though it’s also a solid choice for men. In our tests, we really liked its premium-quality, roomy upper and the stability it provides during runs. However, we found the shoe to be quite firm underfoot, which might not be everyone's preference. Additionally, considering its high price, we were concerned about its durability.

Pros

  • Highly stable
  • Wide forefoot design
  • Premium materials
  • Lightweight
  • Excellent lockdown
  • Enhanced tongue comfort
  • Rare women-first design

Cons

  • Questionable durability
  • Firm midsole
  • Limited breathability

Audience verdict

87
Great!

Who should buy

After testing the Cloudspark from On in the lab, we highly recommend it for:

  • Those with a wide forefoot seeking a daily trainer that balances a firm midsole with good comfort.
  • Women with mild stability needs who prefer not to sacrifice weight for support.
  • Heel strikers who demand top-quality materials and substantial cushioning in a daily trainer.

On Cloudspark

Who should NOT buy

While we liked On's approach to creating the Cloudspark with a focus on women's data, we do not recommend it as the best daily trainer for men within the brand. Inside On's lineup, we believe there are better choices like the Cloudsurfer 7 for similar budgets, and the Cloudmonster Hyper for those willing to spend a bit more.

Additionally, while many may appreciate this shoe, we believe that those of you who dislike a firm midsole will probably ultimately return it. For a women-friendly daily trainer that better balances comfort and support, we highly recommend the ASICS GT 2000 12 or the Hoka Arahi 7 instead.

On Cloudspark cut

Breathability

During our smoke-pumping test, we observed that the upper offers decent ventilation, particularly through the medial sides—ideal for those prone to blisters in that region or along the arch. Yet, the toebox ventilation left us wanting more, leading us to rate it 3/5 overall.

Utilising a light, we discovered the cleverly-designed ventilation strips by On. These strips not only look outstanding but also boast a high quality that sets them apart from the average brand's simpler perforated designs.

We then used a microscope to examine these ventilation areas more closely.

On Cloudspark mesh

We found that On strategically thinned the yarns in these areas while maintaining the overall structure of the upper, enhancing both comfort and durability.

On Cloudspark mesh detail

In our final evaluation of the upper, we appreciate that On maintains its market position with premium pricing.

However, we found that the superior quality of the upper certainly justifies the cost, at least for now.

Test results
Cloudspark 3
Average 3.8
Compared to 234 running shoes
Number of shoes
1
Breathability
5

Durability

Toebox durability

Our initial test with the Dremel always targets the toebox, a common area of concern where runners often experience wear from their toenails.

The Cloudspark earned a 3/5 in this evaluation thanks to its dual-layer upper—not a poor score, yet somewhat underwhelming for a shoe marketed as premium, where we expected a bit more durability.

On Cloudspark Toebox durability
Test results
Cloudspark 3
Average 2.4
Compared to 168 running shoes
Number of shoes
1
Toebox durability
5

Heel padding durability

The heel padding of the Cloudspark disappointingly falls short in durability.

In our rigorous testing—our second standardised Dremel test where we apply consistent force and time to this area—the shoe earned a dismal 1/5 score, placing it firmly at the bottom of our rankings.

Test results
Cloudspark 1
Average 3.2
Compared to 164 running shoes
Number of shoes
1
Heel padding durability
5

Outsole hardness

Turning our focus to the outsole, we discovered that the Swiss brand adopts a cautious strategy. Our measurements showed a hardness of 88.9 HC, indicating a formulation that tends towards the harder side, potentially sacrificing some grip.

On Cloudspark outsole

Thes outsole is quite interesting. It combines rubberized foam with substantial amounts of hard rubber and features a prominent, central groove that shows the Speedboard plate, boosting flexibility.

On Cloudspark Outsole hardness
Test results
Cloudspark 88.9 HC
Average 80.5 HC
We use an average of four tests. The photo shows one of those tests.
Compared to 285 running shoes
Number of shoes
52.1 HC
Outsole hardness
93.0 HC

Outsole durability

We used the Dremel for a third—and final—time to test the toughness of the rubber.

Unfortunately, the results were slightly underwhelming once more regarding durability. While a wear of 1.1 mm isn't disastrous, we expected much better performance from an 88.9-HC rubber.

On Cloudspark Outsole durability
Test results
Cloudspark 1.1 mm
Average 0.9 mm
Compared to 146 running shoes
Number of shoes
0.0 mm
Outsole wear
2.0 mm

Outsole thickness

On seems aware of the type of rubber they were using, as they installed a thick 3.9-mm layer beneath the midsole.

On Cloudspark rubber

Although this solution isn't perfect—it does add some weight—it compensates for the slightly lower durability we previously noted.

On Cloudspark Outsole thickness
Test results
Cloudspark 3.9 mm
Average 3.2 mm
Compared to 304 running shoes
Number of shoes
0.0 mm
Outsole thickness
6.6 mm

Weight

Although the shoe carries some additional weight due to the thick rubber, it’s not overly cumbersome.

The rest of the shoe compensates well, allowing On to maintain a weight just below the 10-oz threshold at only 269g.

On Cloudspark Weight
Test results
Cloudspark 9.49 oz (269g)
Average 9.38 oz (266g)
Compared to 305 running shoes
Number of shoes
5.26 oz (149g)
Weight
12.56 oz (356g)

Cushioning

Heel stack

As a daily trainer primarily designed for women—which are usually heel strikers—we expected a high heel stack in the Cloudspark. Our measurements confirmed a generous 34.6 mm, providing ample cushioning for any runner, but it could be considered even maximalist for women because they generally weigh less than men.

It’s also important to note that while On sells the Cloudspark for both men and women, the brand says that this model was conceptualised with a female-centric design, focusing on their specific footstrike and biomechanics.

On Cloudspark Heel stack
Test results
Cloudspark 34.6 mm
Average 33.7 mm
Compared to 304 running shoes
Number of shoes
7.6 mm
Heel stack
45.7 mm

Forefoot stack

We also measured the forefoot, which aligns with the average height found in most running shoes designed for daily runs. This design approach seems sensible to us. We recorded its height at 26.0 mm.

On Cloudspark Forefoot stack
Test results
Cloudspark 26.0 mm
Average 25.0 mm
Compared to 304 running shoes
Number of shoes
7.6 mm
Forefoot stack
36.9 mm

Drop

While On typically designs shoes with a 6-mm drop, they adapted their approach this time due to the women-driven design we mentioned earlier. And given that women often are heel strikers, it makes practical sense to introduce a bit more offset, right?

Although the brand advertises the drop at 8 millimetres, our measurements came in slightly higher at 8.6 mm. This difference is negligible and the feel is comparable, so we consider this spec confirmed.

On Cloudspark Drop
Test results
Cloudspark 8.6 mm
Average 8.7 mm
Compared to 304 running shoes
Number of shoes
-0.8 mm
Drop
16.1 mm

Insole thickness

Inside the shoe, we uncovered an insole that proved lightweight and comfortable, measuring 4.0 mm in thickness.

On Cloudspark Insole thickness
Test results
Cloudspark 4.0 mm
Average 4.5 mm
Compared to 300 running shoes
Number of shoes
1.5 mm
Insole thickness
7.3 mm

Midsole softness

Note: a low durometer measurement equals a soft material, whereas a high measurement means it's firm.

We explored the midsole, which, like most On running shoes, incorporates CloudTec technology featuring multiple pods. These pods aim to lighten the shoe and enhance foam compression.

However, the necessity of these pods becomes apparent with the Cloudspark, as the foam registered a really firm 34.8 HA.

Although this might be a strategic choice to counter lateral collapse—as women often pronate more due to their hip and knee biomechanics—it seems excessively firm to us, and would benefit from getting below the 30-HA threshold.

On Cloudspark Midsole softness
Test results
Cloudspark 34.8 HA
Average 21.4 HA
We use an average of four tests. The photo shows one of those tests.
Compared to 232 running shoes
Number of shoes
8.5 HA
Midsole softness (soft to firm)
41.5 HA

Secondary foam softness

Note: a low durometer measurement equals a soft material, whereas a high measurement means it's firm.

The Cloudspark features a dual-foam configuration, with the secondary material being even firmer  and denser than the primary at 38.9 HA. This level of firmness is extremely pronounced and will primarily appeal to those who prefer a very solid, steel-like feel underfoot.

On Cloudspark Secondary foam softness
Test results
Cloudspark 38.9 HA
Average 24.9 HA
We use an average of four tests. The photo shows one of those tests.

Midsole softness in cold

Note: a low durometer measurement equals a soft material, whereas a high measurement means it's firm.

On is one of the brands with an exceptionally high percentage of shoes featuring reflective elements (usually the brand's logo) in their lineup, and we were excited to discover them again in the Cloudspark.

Test results
Cloudspark 40.1 HA
Average 26.5 HA
Compared to 231 running shoes
Number of shoes
12.4 HA
Midsole softness in cold (soft to firm)
51.3 HA

Difference in midsole softness in cold

In colder temperatures, the midsole only became slightly firmer. We found a modest 15.5% increase from the room temperature reading, which is indeed a superb performance.

On Cloudspark Difference in midsole softness in cold
Test results
Cloudspark 15.5%
Average 25.5%
Compared to 231 running shoes
Number of shoes
0%
Difference in midsole softness in cold
100%

Plate

Like many On running shoes, the Cloudspark incorporates Speedboard technology, but this time we noticed that the Swiss brand has made two major adjustments—it's made from a nylon-blend material for improved flexibility and stops in the midfoot instead being a full-length plate. It also serves as a barrier between the primary and secondary foams.

On Cloudspark Plate

Stability

Lateral stability test

While we found the midsole a tad firm, this characteristic undoubtedly brings notable advantages. The most prominent among them is the remarkable stability we experienced in the Cloudspark, which is impressive for a shoe that isn't particularly wide.

On Cloudspark reinforcement

We also want to emphasise the substantial reinforcement that On has designed, wrapping from the heel to the forefoot, as it also contributes to keep to achieve more stable landings.

Torsional rigidity

We rated the torsional rigidity of the Cloudspark at 4 out of 5, which significantly contributes to delivering a stable ride. However, this rigidity slightly reduces comfort, particularly at very slow paces.

Test results
Cloudspark 4
Average 3.2
Compared to 283 running shoes
Number of shoes
1
Torsional rigidity
5

Heel counter stiffness

We anticipated a rigid heel counter, but instead, we discovered a more flexible design focused on comfort (2/5). While this flexibility might slightly compromise stability, the combination of firm foam and high torsial stiffness likely enabled On to adopt this softer approach.

In our view, this rare combination makes it ideal for those with Achilles tendon issues who want stability without a firm heel counter.

Test results
Cloudspark 2
Average 2.8
Compared to 267 running shoes
Number of shoes
1
Heel counter stiffness
5

Midsole width in the forefoot

When we began discussing stability in this lab review, we noted that the shoe wasn't particularly wide—certainly not as wide as many stability shoes typically are. This narrower fit is also a hallmark of On's design strategy.

After measuring the forefoot, we found a width of 114.6 mm, aligning it closely with the dimensions typical of most neutral running shoes.

On Cloudspark Midsole width in the forefoot
Test results
Cloudspark 114.6 mm
Average 113.7 mm
Compared to 305 running shoes
Number of shoes
100.5 mm
Midsole width in the forefoot
126.5 mm

Midsole width in the heel

Shifting our digital callipers to the forefoot confirmed the trend, as a measurement of 91.5 mm is another typical dimension for this type of shoe.

On Cloudspark Midsole width in the heel
Test results
Cloudspark 91.5 mm
Average 90.5 mm
Compared to 305 running shoes
Number of shoes
74.9 mm
Midsole width in the heel
106.6 mm

Flexibility

Stiffness

Striving to balance stability with comfort, the Cloudspark has shown that optimal torsional stiffness is essential. But, what about longitudinal stiffness?

During our evaluation, it required 28.8N of force to flex the shoe to a 90-degree angle. This level of stiffness might be an overkill for those seeking an ultra-flexible shoe suitable for a variety of activities, including walking or cross-training.

Test results
Cloudspark 28.2N
Average 29.2N
We use an average of four tests. The video shows one of those tests.
Compared to 287 running shoes
Number of shoes
2.2N
Stiffness
94.4N

Difference in stiffness in cold

After placing the Cloudspark in our freezer for another long 20 minutes to mimic cold conditions, we found that the shoe became 42% stiffer, which is not ideal.

Test results
Cloudspark 42%
Average 35.9%
Compared to 287 running shoes
Number of shoes
0%
Difference in stiffness in cold
148%

Size and fit

Toebox width at the widest part

As we noted in our guide on running shoe uppers, women's feet differ from men's, primarily featuring a wider forefoot and a narrower heel.

On Cloudspark feet

To ensure a consistent comparison, we test all shoes in a US men's size 9. This approach allows us to fairly evaluate every shoe under the same standard. So yeah, these are not (obviously) women's legs.

Given that this shoe was designed with women's feet in mind, we expected a broader-than-usual forefoot, and indeed, we measured it at 100.1 mm.

On Cloudspark Toebox width at the widest part
Test results
Cloudspark 100.1 mm
Average 98.4 mm
Compared to 305 running shoes
Number of shoes
89.5 mm
Toebox width at the widest part
109.1 mm

Toebox width at the big toe

We also measured the big toe area with our callipers at 78.9 mm. This is a standard, no-risk design choice aimed at accommodating the majority of foot shapes of both genders.

On Cloudspark Toebox width at the big toe
Test results
Cloudspark 78.9 mm
Average 78.2 mm
Compared to 179 running shoes
Number of shoes
60.4 mm
Toebox width at the big toe
92.5 mm

Tongue: gusset type

A key feature we need to find in a premium daily trainer is the gusseted—attached to the sides—tongue, and we found that the Cloudspark ticks the box.

Test results
Cloudspark Both sides (full)

Comfort

Tongue padding

We've discovered that many On road shoes—like the Cloudmonster Hyper—feature notably thin tongues, which we found less comfortable on the instep during long runs.

On Cloudspark laces

Fortunately, this time we encountered a thicker tongue, measuring 4.9 mm, offering a significantly improved experience for our instep!

On Cloudspark Tongue padding
Test results
Cloudspark 4.9 mm
Average 5.6 mm
Compared to 302 running shoes
Number of shoes
0.5 mm
Tongue padding
14.2 mm

Heel tab

Like many other models from On, the Cloudspark also features the noticeable absence of a heel tab—a common trait among their streamlined, uncomplicated design.

On Cloudspark Heel tab
Test results
Cloudspark None

Removable insole

A nice bonus of the Cloudspark is the removable insole—this choice simplifies the process of integrating your own aftermarket orthotic inserts if needed.

On Cloudspark Removable insole
Test results
Cloudspark Yes

Misc

Reflective elements

On is one of the brands with an exceptionally high percentage of shoes featuring reflective elements (usually the brand's logo) in their lineup, and we were excited to discover them again in the Cloudspark.

Test results
Cloudspark Yes