Origins
Hardstyle was influenced by hard trance, gabber, acid house and hard house. Hardstyle has its origins in the Netherlands where artists like Dana, Pavo, Luna and The Prophet, who produced Hardcore, started experimenting while playing their Hardcore records. The first Hardstyle events, like Qlubtempo took place at the beginning of the 21st century. The first few years of Hardstyle were characterized by a tempo of around 140-150 BPM, a compressed kick drum sound, a short vocal sample, a screech and the use of a "reverse bass", which can be heard on the offbeat after each kick.
After several successful editions of Qlubtempo and Qlimax, Q-dance registered the word hardstyle as their brand on the 4th of July 2002.
Around 2002, more Hardstyle labels emerged. Fusion (with artist as DJ Zany and Donkey Rollers) and Scantraxx (founded by Dov Elkabas a.k.a The Prophet) are two of the Dutch labels that started to bring out Hardstyle tracks around that time.
Around 2004-05 the genre became more melodic and uplifting, somewhat faster (usually 150 BPM), and distorted, sharp kick drum sounds were added. Many producers started to pitch-shift a distorted kick drum to create a melodic bassline that usually plays in pitch with a typical hard trance supersaw or a thinner electro house synth melody. The melody often is in tuplet form, which gives the genre a pulsating rhythm, whereas older Hardstyle as well as other genres such as jumpstyle have more basic melodic structures to them. Thus, nowadays many people refer to the older style as early Hardstyle.

Rawstyle
Since around 2008, more terms to identify developments of Hardstyle were introduced. Rawstyle is a type of Hardstyle influenced from Dutch Hardcore or older Hardstyle resulting in darker melodies and deeper-sounding kick drums with more distortion through VST plug-ins such as Devastor, CamelPhat, Ohmicide & TriDirt.

Dubstyle
In early 2010s, a new variation in hardstyle, named Dubstyle was introduced. Dubstyle is the name given to the genre fusion of Hardstyle and Dubstep. Dubstyle tends to have reversed wobble basslines and take the kick styling of hardstyle tracks, while combining them with the rhythm, groove, and dubstep tempo and effects a fusion of elements of hardstyle with a dubstep rhythm, usually a 2-step or a breakbeat rhythm. Because of the sporadic beat in Dubstyle, the bass is often more dragged out and/or it doesn't follow a strict offbeat pattern that regular Hardstyle incorporates, which in turn results in Dubstyle basslines bearing similarities to dubstep basslines. The first mainstream Dubstyle track was Headhunterz & Brennan Heart's "The MF Point of Perfection".

Origins
"Gabber" is an Amsterdam Bargoens slang that means "mate", "buddy", "pal" or "friend". The music got its name from an article in which Amsterdam DJ K.C. the Funkaholic was asked how he felt about the harder Rotterdam house music scene. He's supposed to have answered "They're just a bunch of gabbers having fun". DJ Paul Elstak from Rotterdam read this article and on the first Euromasters record (released through Rotterdam Records), he engraved in the vinyl "Gabber zijn is geen schande!" translating as "it's not a disgrace to be a gabber!". The word gained popularity in the Rotterdam house scene and people started to call themselves 'gabbers'.
The Mainstream hardcore sound derives from the early hardcore (still called gabber at the time). In the late 1990s, the early hardcore became less popular than the Hardstyle. After surviving underground for a number of years, in 2002 the gabber regained some popularity in the Netherlands, although the sound is more mature, darker, and industrial. Some producers started embracing a slower style characterized by a deeper, harder bass drum that typically had a longer envelope than was possible in the traditional, faster style. In this aspect, this new form of gabber obviously cannot be considered less powerful than its precursor. This newer sound was referred to as "New Style" or "Mainstream" and as the tempo got slower and slower it began to become similar to hard house. Many hardcore enthusiasts hated hard house and the club scene it typified, and frequently DJs would be booed by one group of fans and cheered for by another at the same party, depending on the tempo and style of music they were playing. This is similar to the rivalry and mutual dislike that surfaced earlier between fans of "regular" hardcore and happy hardcore. Eventually the two styles met in the middle, and most gabber today is produced in a range of 160-180 bpm. This style is typically a bit slower than the Rotterdam style of the mid-1990s.

Style
Angerfist, one of the most famous DJs of mainstream hardcore.
Mainstream hardcore is characterized by its bass drum sound. Essentially, it comes from taking a normal synthesized bass drum and over-driving it heavily. The approximately sinusoidal sample starts to clip into a square wave with a falling pitch. This results in a number of effects: the frequency spectrum spreads out, thus achieving a louder, more aggressive sound. It also changes the amplitude envelope of the sound by increasing the sustain. Due to the distortion, the drum also develops a melodic tone. It is not uncommon for the bass drum pattern to change pitch throughout the song to follow the bass line. Lots of tracks rely on a clean, detuned supersaw lead, similar to uplifting trance.

Recent developments
In the 2000s, some producers produced neither Nu Style or oldschool gabber. They focused again on speed, with tracks normally go over 200 bpm. Subgenres have developed where scenes exhibit certain musical traits and are mainly defined by their kick drum sound. These subgenres include:
-Terrorcore
Uses same highly distorted kick drum as gabber. Tracks are normally minimalistic and non-melodic, and the themes are normally highly aggressive. Artists include DJ Plague, Nordcore GMBH, Noisekick, and Dj Smurf.
-Hardcore Techno
Removes the distortion from the kick drum, in favor of a more natural heavy reverb sound, which is usually affected by a filter. There's usually influence from breakcore, which uses distorted breaks over the 4/4 kick, and a lot of tracks have ambient sounds and a progressive feel. Artists include Hellfish, DJ Producer, Bryan Fury, Deathmachine, Teknoist, and Scott Brown. Occasionally, UK Hardcore producers try their hand at producing Hardcore Techno, such as Gammer and Brisk & Vagabond. Some UK Hardcore producers also like to put small sections of gabber within their tracks. Fans of this include Hixxy and Re-Con. Other Hardcore Tachno artists such as the 'Gabba Surgeons' draw from a whole myriad of genres including drum & bass, electro and house. There is also a cult following of Japanese hardcore techno, also known as j-core, where the general themes include sound samples from anime and videogames, arranges of Touhou Project soundtracks, and a greater emphasis on melody than its Western counterpart.
-Speedcore
A faster type of gabber usually 300 bpm or faster. The term "splittercore" is usually used for speedcore tracks of 500-900 bpm. The term "extratone" is used for tracks of over 1000 bpm; though the usefulness of this distinction is debatable due to the capacity of human ears to detect the differences in such high beats per minute.
Cybergrind is a mixture of gabber (as well as other electronic styles such as industrial, intelligent dance music, techno, and/or power noise) and grindcore, performed by The Berzerker and Genghis Tron.