UTMB, CCC, TDS, OCC: How to make sense of the crazy Mont-Blanc week?

Every year, at the end of August, Chamonix transforms. For one week, this Haute-Savoie town becomes the undisputed world capital of trail running. While the general public mainly knows the acronym "UTMB" (Ultra-Trail du Mont-Blanc), you should know that this term now refers to two things: the historic flagship race, but also the overall event, a true global summit of the discipline.

With more than eight different race formats spread over a hectic week and nearly 10,000 runners from all corners of the globe, it’s completely normal to get a bit lost. What’s the difference between the legendary UTMB and the CCC? Why is the TDS considered by many as the toughest? And what does the acronym OCC hide?

Whether you're a passionate follower watching the event live, a supporter on the side of the trails, or a future runner dreaming of getting a race bib, here’s a complete breakdown of the four major races to fully understand this extraordinary week.

The big comparison table (For a quick glance)

Before diving into the specifics and spirit of each race, here is a visual summary. This table lets you immediately identify the distances, elevation gain, and profile of the "Fantastic Four" of the week.

(Note: distances and elevation gains may vary by a few kilometers from year to year depending on route changes and weather).

Decoding the "Fantastic Four"

While the table allows you to compare the figures, it says nothing about the soul of these races. Because behind the kilometers and elevation gain hide adventures with strong characters. Here's what makes up the DNA of each one.

The UTMB (Ultra-Trail du Mont-Blanc): The absolute myth

This is the race that changed everything, the one through which trail running shifted to a new dimension. The UTMB is not just a sporting event, it is a journey.

• The course: It offers the complete tour of the Mont-Blanc massif. Starting from Chamonix, runners cross three countries (France, Italy, and Switzerland) before returning to their starting point, thus closing a legendary loop of over 170 km.
• The difficulty: Beyond the 10,000 meters of positive elevation gain, the real difficulty of the UTMB lies in managing effort over time. For the vast majority of the pack, this means spending two full nights outside, fighting sleep, and adapting to often unpredictable alpine weather (it can be very hot during the day and freezing at night at altitude).
• The atmosphere: Unmistakable. The start at Triangle de l'Amitié square, with thousands of spectators and the haunting music of Vangelis (Conquest of Paradise), gives chills even to the toughest. The finish under the arch is often described as one of the most intense moments in a runner's life.

The TDS (Sur les Traces des Ducs de Savoie): The wildest and most feared

Don't be fooled by its "shorter" distance than the UTMB. In the trail world, the TDS has the reputation of being the most demanding technically.

• The course: Starting from Courmayeur (Italy), it turns towards the Beaufortain region in France. It’s a magnificent route, far from densely populated valleys, offering breathtaking views of preserved massifs.
• The difficulty: It’s a concentration of high mountain terrain. The trails are less "runnable" than on the UTMB. You have to face steep climbs, technical and rocky descents where every step counts.
• The spirit: This is the race for purists and mountaineers. Less publicized than its big sister, it attracts runners seeking authenticity, toughness, and solitude in the face of vast summits.

The CCC (Courmayeur - Champex - Chamonix): The little sister turned giant

Created in 2006 to relieve the UTMB, the CCC was long seen as the consolation prize. Today, that is totally false: it has become one of the most prestigious 100 km races worldwide.

• The course: It covers the second half of the UTMB route. The Italian start in Courmayeur is quickly followed by one of the major difficulties: crossing into Switzerland via the dreaded Grand Col Ferret, at over 2,500 meters altitude.
• The difficulty: It’s a race with two faces. Up front, among elites (who complete the course in around ten hours), the pace is furious and extremely intense. At the back, for amateurs, it is a true endurance challenge of a day and a night, with long exhausting climbs.
• The stakes: It now acts as the "World Final" for the 100K category in the UTMB World Series circuit. The level is stratospheric.

The OCC (Orsières - Champex - Chamonix): The explosive one

The youngest of the "big" races (in 2014), the OCC has established itself as the marathon format of the global trail running summit.

• The course: The start is given in Switzerland, in the charming village of Orsières. The route then joins that of the CCC and the UTMB to reach Chamonix via balconies offering stunning views of the massif.
• The specificity: With "only" 55 km and 3,500 meters of elevation, the OCC is run during the day. For professionals, it’s a true giant sprint of 5 hours where accelerations are constant. Any weakness here is fatal to the ranking.
• Accessibility: For amateur runners, it’s the perfect entry point. It allows you to experience the UTMB ambiance, to pass under the legendary arch in Chamonix, to enjoy flawless organization, all without having to face hallucinations and the extreme fatigue of a sleepless night in the mountains.

The other races of the week: It’s not just about the ultras!

While the "Fantastic Four" grab most of the media attention, the Mont-Blanc week pulses with other equally fascinating formats, allowing every type of trail runner to find their place.

• The PTL (La Petite Trotte à Léon) – ~300 km / ~25,000 m D+: It’s not a race in the strict sense, but an extreme team adventure of two or three people. With no ground markings (orientation by GPS only) and almost total autonomy, participants make a large extended tour of the massif. An extraordinary challenge requiring exceptional mountain sense and commitment.
• The MCC (From Martigny-Combe to Chamonix) – ~40 km / ~2,300 m D+: Originally created for volunteers, partners, and locals of the Mont-Blanc area, this event traditionally opens the festivities on Monday. Less selective at registration, it offers a festive and local profile much appreciated, while still presenting a fine sporting challenge.
• The ETC (Experience Trail Courmayeur) – ~15 km / ~1,200 m D+: The shortest format of the week, based in Italy. It is a fast and demanding route in the heart of the Courmayeur pastures, designed for explosive athletes or those wanting to discover the event’s atmosphere in a condensed format.
• The YCC (Youth Chamonix Courmayeur): Formats adapted and reserved exclusively for young categories (minimes, cadets, juniors, espoirs). It combines a prologue and a line race to showcase the future champions of the discipline.

Runners or spectators: How to enjoy the event?

Such an event doesn’t happen by chance, whether you’re on one side or the other of the tape.

For spectators and enthusiasts (on site or remotely): If you’re following the race from your couch, know that the organization has set up an exceptional system via the UTMB Live platform. Thanks to onboard cameras, drones, expert commentators, and real-time GPS tracking of each runner, the viewing experience is complete. For spectators on site, using the valley’s public transport (the UTMB Bus shuttles) is mandatory to avoid road saturation. Some spots are particularly magical for cheering on the runners: Les Contamines-Montjoie at nightfall, the buzzing Italian base camp in Courmayeur, or the peaceful lake of Champex in Switzerland.

Did you know? The obstacle course for future runners: You don’t register for the major Mont-Blanc races on a whim. Applicants must first hold a valid "UTMB Index" (which proves their performance level over a similar distance) and secondly collect Running Stones by participating in and finishing races on the world circuit (the UTMB World Series). These "stones" act as tickets for the increasingly selective final lottery due to worldwide demand.

Conclusion

More than a simple succession of bibs and timers, the Mont-Blanc week has established itself as the global crossroads where the legend of trail running is written. From the steep paths of the formidable TDS to the daytime sprint of the OCC, passing through the long heroic ordeal of the UTMB, each distance offers its own philosophy of effort.

Whatever your motivations, the number of kilometers, or the final ranking, crossing the finish line in Chamonix, cheered on by a delirious crowd, remains an achievement suspended in time. A human adventure forever engraved in the legs and mind of those who dare to measure themselves against it.