Differences between a gravel bicycle and a mountain bike (MTB)
For beginner cyclists, telling the difference between a gravel bike and a mountain bike (MTB) can be somewhat confusing. At first glance, both share certain characteristics: wide tires, the ability to leave the pavement, and a robust appearance. However, they are designed with very different purposes and philosophies.
The gravel bikes are intended to offer balanced performance both on the road and off it, as long as the terrain is not too technical or extreme. They are perfect for those looking for versatility: they can ride on dirt roads, forest tracks, and even on paved stretches without any problem. Their strength lies in combining the best of road cycling with an adventurous touch.
On the other hand, mountain bikes —or MTB— are built to take on demanding routes in nature: trails with roots, rocky descents, technical sections, and very uneven terrain. They incorporate front suspension (or full suspension), flat handlebars, and a geometry designed to offer greater stability and control on technical descents or very rough areas.
Although some of the more recent gravel bikes are starting to incorporate light suspension systems and somewhat wider tires, they are still less suitable for extreme mountain biking. Their design prioritizes efficiency over long distances and mixed surfaces, making them ideal for bikepacking or exploration routes where asphalt and dirt are combined.
The gravel bikes have other strengths. They are fast. With lightly treaded tires inflated to about 3 kg, most gravel bikes can roll almost as fast as a road bike. Their frames are light and agile, and the feeling on asphalt is very similar. The drop handlebars and a geometry with a certain racing touch they help in this regard. It is a very fun feeling to ride a gravel at full speed down a track and, at the same time, feel a grip that is reminiscent of mountain bikes. When it comes to competition, mountain biking is much more established than gravel racing, which is still in its early stages. International MTB competitions have existed for decades, and include men's and women's races in multiple modalities, such as Cross-Country (STXC), Marathon, Enduro and Downhill. gravel races, on the other hand, are just starting out and are more about ultra-endurance. The world's most popular competitions usually last between 5 and 10 hours, with routes over 300 km and 3,000 m of elevation gain. Many of the world's best gravel cyclists, at least for now, have been—or are—WorldTour professionals: Laurens ten Dam, Thomas Dekker, Peter Stetina, Ted King... Competition aside, the popularity of gravel skyrocketed just a few years ago. Millions of cyclists around the world rushed to buy bikes, but in many cases without really knowing what they were looking for. Here we present some similarities and differences between gravel bikes and mountain bikes.
Wheels and tires
One of the defining features of gravel bikes is the wide tire clearance, which in many cases allows for tires up to 50 mm. This way, they allow you to ride with a huge variety of tires. In fact, it is common for elite gravel cyclists to swap tires depending on the terrain and technical difficulty of the races. In any case, mountain bike tires play in another league if we compare them with the highest-performing gravel tires. The former are designed to handle bumpy trails, roots, stones, rocks, etc. MTB tires are significantly wider (from 2.2" is usually the norm) and often use more pronounced tread patterns for traction in mud. In addition, they are much thicker and may include sidewalls with puncture protection.
Mountain bike tires play in another league if we compare them with the highest-performing gravel tires.
Although it may seem that a gravel bike with wide, knobby tires is capable of tackling twisty trails, it is actually much less protected against punctures than a mountain bike tire.
Gears and brakes
In reality, there are quite a few similarities between gravel bikes and mountain bikes when it comes to gears and brakes. In fact, gravel bikes have increasingly adopted technologies that used to be exclusive territory of MTB. Single chainring drivetrains or disc brakes are two classic examples. There are endless gear options for both gravel bikes and mountain bikes, and you can find setups that include one, two, or even three chainrings. The world of gravel is still quite divided when it comes to 1x or 2x configurations. Normally, the choice depends on where you ride. If you live on flat terrain, you probably don’t need a 2x setup with a huge cassette. But if you like to push hard on 20% climbs, you’ll look for the widest gear range possible. 
On mountain bikes, the 1x setup is already a standard. Component manufacturers have been able to design an enormous range of cogs in the cassette (from 10 to 50 teeth, for example), which allows you to always find the right gear; it doesn’t matter if you’re going 8 km/h or 35 km/h. Long before road cycling resolved the issue of hydraulic disc brakes, these were already the preferred option in MTB. They offer much greater power, modulation, and durability on trails and paths. gravel bikes picked up the baton from the very beginning.
Frame Geometry
At first glance (and only at first glance), gravel bikes are designed very similarly to road bikes. The rider adopts a position that balances aerodynamics and comfort: not too upright, not too aero. In general, gravel bikes are shorter than mountain bikes, which have slacker head angles and longer wheelbases. MTB models are designed for technical terrain. A longer reach makes them more stable at speed, especially on rough terrain. The slacker head angle helps keep the rider’s center of gravity balanced on steep descents, while short stems and wide handlebars improve leverage and maneuverability. These flat handlebars on mountain bikes also improve grip and stability on jumps or technical terrain, where greater leverage is beneficial.
Suspensions
In general, a conventional gravel bike does not have suspension, although some do. However, even when they do, they have a much shorter travel than a mountain bike. There may be gravel models with 20-30 mm, which have little to do with mountain enduro models with 140 or 170 mm. Unlike gravel bikes, most mountain bikes on the market are divided into two categories: hardtails (or semi-hardtails, to be more precise), with suspension in the fork, and full suspension, with a shock absorber also in the central part of the bike. The former are more affordable, easier to maintain, and have lighter frames, which allows for good performance in cross-country mode and in races where speed and reactivity are sought.
Handlebars
One of the biggest differences between gravel bikes and mountain bikes is their handlebars. gravel bikes usually have curved handlebars similar to road bikes, while mountain bikes use straight handlebars, or with a slight curve. This significantly affects the handling of each bike, as well as the position and comfort of the rider during long hours in the saddle. At the front, gravel bikes provide a very similar feeling to a road bike. The rider can choose between three main positions to place their hands: on the hoods, on the superior part, or in the drops of the handlebar. The tendency is usually to spend most of the time with the hands on the hood covers. From there it is easy to reach the brake and the shifter. With the hands on the top part, it is much more difficult to brake or shift quickly. Placing the hands in the drops provides security and easy access to the brake levers, making it a very common posture on descents. They also offer a more aerodynamic and aggressive riding position. Mountain bikes, on the other hand, use straight handlebars instead of drop handlebars. Depending on the model, they may have a slight curve between the grips and the center of the handlebar, unlike gravel handlebars, which look like ram's horns. 
In the case of MTB riders, the hand position on the handlebar is almost always the same: resting on the grips at each end of the handlebar tube. Some advanced riders have the habit of putting their hands very close to the stem, to narrow their shoulders and adopt an aerodynamic position. Maybe during a flat and non-technical section of a route this can make sense.
Ergonomics and riding position
The handlebars of gravel provide the cyclist with more options to adapt their position on the bike. Unlike the more aggressive position adopted by a road cyclist, gravel bikes have a geometry more oriented towards endurance, allowing them to pedal efficiently without leaning too far forward. There are indeed times when a more aggressive posture is required. In fact, riding while holding the drops of a gravel handlebar allows for better bike control, although it can harm comfort and excessively strain the back, neck, or arm muscles. A common position on a gravel bike is to rest the hands on the brake hoods. Access to the brakes is immediate. However, resting the hands on the tops can offer significant relief when the rider feels tired or experiences discomfort in the lower back area. On the other hand, with the hands in this position, control over the bike is reduced; especially on bumpy roads, sandy trails, or loose gravel. Therefore, it is not advisable to adopt this posture off asphalt or well-packed paths. Bikers usually adopt a very different posture on their MTB bikes, especially conditioned by the flat handlebars and frame geometry. The handlebars are much wider than those mounted on gravel bikes. The most common measurement for an XC mountain bike ranges between 72 and 74 cm, while the handlebars of gravel bikes usually range between 40 and 46 cm, with 44 cm being the most common. As a result, on a mountain bike you pedal with your elbows much more open.
Bikers usually adopt a very different posture on their MTB bikes, especially conditioned by the flat handlebars and frame geometry.
This type of handlebar has its advantages, but also penalizes maneuverability: the longer they are, the slower the steering becomes. In addition, they are less aerodynamically efficient. In fact, there is a type of competition gravel bike specifically focused on speed. Mountain bikes put the cyclist in a relaxed and upright position, which is best for cornering and controlling the bike more safely. However, on winding trails with vegetation, a wide handlebar can cause unexpected impacts. Flat handlebars are not designed for speed. On the other hand, gravel bikes put the cyclist in a somewhat more racing position.