UTMB 2026: What to Watch on the Live Tracker¶
The tracker opens Friday night at 17:45 Chamonix time. Roughly 2,500 runners cross the start line and begin moving into the mountains, and the first position updates start arriving at live.utmb.world.
Standings at kilometer 30 tell you almost nothing. Standings at Courmayeur tell you quite a bit. What happens between Courmayeur and Champex-Lac at 2 AM Saturday tells you everything. The difference is knowing which numbers to watch.
Race Week: August 24 to 30¶
UTMB 2026 is more than one race. The week opens Monday, August 24, with the shorter events on the same trails: MCC, OCC, CCC, and PTL all run before the 100M goes off Friday. If you're following the full week, those races run through the same checkpoints and give you a feel for how the tracker works before the big field goes out.
This post is about the 100M. 174 kilometers, 9,900 meters of climbing through France, Italy, and Switzerland. The cutoff is 46 hours 45 minutes. This edition carries additional weight: it closes the 2026 UTMB World Series Finals, which means runners who built qualifying points through the year have more at stake than a normal edition.
The gun goes at 17:45 local time Friday, August 28. The field leaves Chamonix in daylight and runs into the night. The first finishers come back to Chamonix sometime late Saturday morning. Runners who make the full cutoff have until noon Sunday.
For the checkpoint-by-checkpoint cutoff math: the cutoff post has the full table. This post is about what to watch, not what to fear.
How to Read the Tracker¶
The UTMB live tracker is at live.utmb.world. Once the race starts, it shows each runner's current position, the last checkpoint they passed through, and their elapsed time at that checkpoint.
Two things to watch. Two things to stop watching.
Watch: Gap patterns between runners at each checkpoint. Not the absolute position, the gap. A runner who was 20 minutes behind at Courmayeur and is now 8 minutes behind at Champex-Lac is doing something very different from one whose gap held steady.
Watch: Aid station dwell time. The tracker shows arrival and departure times at major checkpoints. Runners who move through the aid stations faster, especially at Courmayeur, tend to show up again in stronger positions by Champex-Lac.
Stop watching: Overall standing in the first 30 kilometers. Early pack positions shift constantly and reveal almost nothing about who finishes well.
Stop watching: Pace per kilometer in the opening segment. The early pace is crowd pace on flat roads. It disappears at the first major climb.
What you are looking for is whether gap patterns are compressing or expanding, and at which specific checkpoint they start to move.
Courmayeur, km 80: The First Real Reveal¶
Courmayeur is in Italy, approximately 80 kilometers in. Getting there requires Col du Bonhomme, Col de la Croix du Bonhomme, and Col de la Seigne at around 2,516 meters. By the time a runner arrives in Courmayeur, they have been moving for somewhere between 9 and 15 hours depending on their pace in the broader field.
The question at Courmayeur is not who arrived first. It is what they look like when they get there.
Runners who arrive at Courmayeur with calm movement, still eating, spending 10 to 15 minutes in the aid station before leaving, tend to come back through Chamonix. Runners who look like they won the first 80 kilometers, spending 30 minutes or more sitting down, tend not to finish where they arrived.
The tracker reveals this through dwell time. If a runner who was top 5 at kilometer 30 is spending substantially longer at Courmayeur than the runners just behind them, that gap is about to close on the other side of the border.
Arrival window and what to watch at three key checkpoints:
| Checkpoint | Distance | Past Elite Arrival Range | What to Watch For |
|---|---|---|---|
| Courmayeur | ~km 80 | ~9 to 15 hrs into race | Aid station dwell time; gap to runners behind; position shift since km 30 |
| Champex-Lac | ~km 125 | ~16 to 26 hrs into race | Whether Courmayeur gaps are growing or closing; who held through the night |
| Vallorcine | ~km 157 | ~28 to 38 hrs into race | Movement vs. survival; who is running the descents vs. walking them |
These windows come from past UTMB editions and describe the range across the competitive field, not a single runner's expected time. The course record runs faster at the front; mid-pack runners run slower.
A note on the Courmayeur-to-Champex-Lac segment. The distance is roughly 45 kilometers and includes Grand Col Ferret at around 2,537 meters, crossing from Italy into Switzerland through La Fouly and Champex-Lac. That is not just added mileage. For most of the field, the entirety of that segment runs in the dark. What happens there is the subject of the next section.
After Midnight: Why the Night Section Decides It¶
Between Courmayeur and Champex-Lac, the race crosses the Swiss border. Col de la Seigne going into Italy, Grand Col Ferret coming out into Switzerland. The ground between those passes is technical and dark for nearly every runner who travels through it.
For front runners, the crossing happens late Friday night into early Saturday morning, roughly midnight to 4 AM Chamonix time. For mid-pack runners, it runs Saturday morning to Saturday afternoon. For back-of-pack runners, this may be their second night on the mountain.
What the tracker shows during these hours is more diagnostic than any other segment of the race. The splits from Courmayeur to Champex-Lac tell you which runners are still executing versus which are managing.
A runner who moved through this segment with consistent inter-checkpoint times was still moving in the dark the same way they moved in daylight. A runner whose splits lengthen substantially through this section, 20 to 30 extra minutes added between each tracking point compared to their earlier pace, was dealing with the convergence of accumulated fatigue, sleep pressure, and elevation that this particular section applies.
That convergence is what UTMB is. Sleep deprivation typically peaks somewhere between 18 and 24 hours into a race. For most of the field, that window lands on the Italian-Swiss border. The night sections of ultras are where positions that looked settled stop looking settled.
Two signals to watch on the tracker in those hours:
A runner who held steady positions from Chamonix to Courmayeur and is gaining positions on the way to Champex-Lac ran the first 80 kilometers within their capacity. A runner who was gaining positions until Courmayeur and is now losing them ran the first 80 at a cost they are paying back.
By the time the tracker shows arrivals at Champex-Lac, the back half of the race is set. Not finished, but set. The positions at Champex-Lac hold more often than they change in the final push to Chamonix.
The 2026 Field: Names to Follow on the Tracker¶
A tracker list is easier to follow when you know what story each name is running. Five runners in the 2026 field, and the pacing question their tracker line answers.
Kilian Jornet. His 2022 course record of 19:49 is the number the tracker line gets measured against. What his line reveals is how he uses the technical terrain between the cols. His efficiency at elevation and on rough ground tends to produce consistent inter-checkpoint splits through the Italian section, where other front runners sometimes slow relative to the climbs already behind them. His Courmayeur arrival time tells you whether this is a record-paced day or a controlled one.
Jim Walmsley. He has recalibrated his approach at UTMB across multiple editions. He has the leg speed to be at Courmayeur in the front group, but 9,900 meters of climbing redistributes pace differently than his fastest flat ultra performances. His tracker line answers one question: did the Courmayeur arrival leave him with a second half to run, or a second half to manage?
Courtney Dauwalter. Multiple UTMB wins. The story her tracker line tells is less about where she is at Courmayeur and more about what the gap looks like by Champex-Lac. Her back-half pacing in past editions produced position gains that the kilometer 80 standing did not predict. If she is not leading at Courmayeur, check again at Champex-Lac before drawing conclusions.
Croft. A technical climber whose most consistent splits in races of this type tend to appear through the Swiss section from Champex-Lac to Trient. Watch the tracker between those two checkpoints for where that pace holds relative to whoever is ahead.
Bouillard. A French runner at home on this course. His Courmayeur arrival and dwell time are the signal: runners who know this course know exactly how long to spend at that aid station. A short stop from Bouillard at Courmayeur is a better signal than a fast split into town.
The Front-Half / Back-Half Ratio¶
At 174 kilometers, Courmayeur at kilometer 80 is close enough to halfway to use as the practical marker. In a well-run UTMB, the back half takes more time than the front half. The question is how much more, and where those extra minutes accumulate.
Past UTMB editions show a consistent pattern. Runners who arrived at Courmayeur in the fastest 10 to 15 percent of the field but outside the top three overall positions tended not to finish inside the top 10. Running to position early costs the back half.
The ratio matters more than the pace. Three illustrative tracker scenarios:
| Scenario | Front Half (0 to km 87) | Courmayeur Arrival | Back Half (km 87 to finish) | What the Tracker Shows |
|---|---|---|---|---|
| Aggressive front | Very fast relative to field | Near top 5, long dwell (30+ min) | Slower: positions drop after the night section | Gap to leaders grows through Champex-Lac and beyond |
| Controlled | Moderate relative to field | Top 10, short dwell (10 to 15 min) | Segment times close to front half | Positions hold or gain from Champex-Lac to Chamonix |
| Late surge | Steady: mid-pack into Courmayeur | Efficient exit, short stop | Front and back halves roughly equivalent | Near-equal splits; uncommon at 174km given the climbing concentration |
These are patterns, not predictions. The purpose of the table is to give you a frame for what the tracker is showing when a runner's position starts to move.
One number the tracker does not show directly but you can calculate: note the elapsed time when any runner passes Courmayeur, then compare it to their finish time. A finish time under 1.5 times the Courmayeur elapsed time usually means the runner ran the back half within themselves. A finish time above 1.7 times the Courmayeur elapsed time usually means the back half cost more than planned.
This ratio applies at 100 miles just as it applies at 50K. The course distance changes the absolute numbers. The pattern of what a controlled first half looks like relative to an aggressive one does not change with distance.
Two Things to Steal for Your Own Racing¶
The tracker is the most detailed public record of elite pacing behavior available anywhere. Here is what to carry into your own racing from watching it.
The Courmayeur principle. In your own racing, the Courmayeur is whatever checkpoint sits nearest the halfway point. The tracker shows you what it looks like to arrive there correctly: calm movement, short time in the aid station, a gap to the next runner behind you that did not require pushing to build. Runners who arrive at the halfway checkpoint looking like they won the first half tend not to finish where they arrived. Runners who arrive looking like they have the second half left usually do.
This applies at 50K with the same force as at 174 kilometers. The names on the halfway split sheet at a 50K are not the same names on the finish sheet, and the reason is almost always Courmayeur-shaped: one group spent the first half buying time they paid back in the second.
The night pacing principle. The tracker lines that hold through the post-midnight segment between Courmayeur and Champex-Lac show something consistent: runners who slowed their effort slightly and kept eating held their positions. Runners who pushed through the fatigue and the dark and the climbing without adjusting their effort lost positions they did not recover.
In your own racing, the night equivalent is whatever segment arrives when you are most tired and farthest from the finish. Slowing slightly and eating something at that point preserves the back half. Pushing through it produces the biggest deficit of the race.
If the pacing framework behind this is useful for your own data, the race splits post-mortem post walks through how to read those patterns after a race. For anyone in a training build toward UTMB or a similar race, the final training block post covers the preparation side without repeating what is here.
If you want to see what your own training history says about the kind of race you can run, navrun.app turns the runs you have already done into a picture of where you are. Race-day strategy, for pacing your specific race, is on the paid side.
Watch the tracker Friday night. The mountain will show you the rest.