The Jedi lightsaber forms are canon

Ahsoka Tano's lightsaber fighting style

Star Wars lightsaber combat is depicted in many different forms (e.g. Form II: Makashi is linked there).

There are many different lightsaber guard poses used in the Star Wars canon and also in the expanded universe / legends.

Her primary form is an acrobatic rendition of Jar'Kai, which may rely heavily on the principles of Form IV: Atarus. This is pretty clear from observing their mechanics in the TV series. Her guard posture with one blade in the back and one in front is unconventional by the standards of the Jedi of the Old Republic. nor is it similar to Starkiller's variant of Jar'Kai, which seems to rely heavily on Form VII: Juyo.

  • Starkiller (right) uses a reverse guard with Form V: Shien in Star Wars: The Force Unleashed:

  • In Star Wars: The Old Republic (roughly 3,500 years before the original trilogy), Jedi sages and Sith wizards hold their blades to the right and angled at about the same angle as the thigh:

Even in the Old Republic, Jedi Guardians who use Form III: Soresu often hold their blades to their dominant side, mostly perpendicular to the ground but angled slightly backwards:

  • Those who are still learning Form I: Shii-cho and wise masters who want to pretend that they are less skilled than they actually are often use what is perhaps the most "obvious" guard (first demonstrated in the Duel of Masters, Vader vs. Obi- Wan, in Episode IV). Here Kyle Katarn uses standard vertical shii-cho protection to the front:

  • Here Anakin Skywalker uses the other style of Form V, Djem'so, against Darth Tyrannus' Form II: Makashi (note that Darth Tyrannus is holding his blade with one hand, a tell-tale sign for using Form II):

Developing lightsaber combat through real chronological history of the Star Wars franchise

This is not an exhaustive list of guards that have been used in Star Wars media, and it definitely seems that Forms saw more variety than games and the prequel trilogy evolved lightsaber combat into an art form with more acrobatics and impressive looks rather than the comparative kinematics boring fights in episodes IV and V.

By the end of Episode VI, in which Luke convincingly uses an offensive lightsaber style - perhaps Form IV: Ataru - against Darth Vader's overt Djem'so, they were already tending towards a more dramatic lightsaber fight (note the sportier stance Luke takes here in comparison to that the "statuesque" linear positions in Episode IV):

It was really the Star Wars games and novels that gave these lightsaber styles some systematization, not so much the movies. This is true of much of the Star Wars lore. Unfortunately, the fact that it wasn't presented in a theater puts it down in the minds of some viewers of Star Wars "canonicality", but take it for what you want; You're already watching a TV show instead of a movie. :) :)

Backstage

From the point of view of a writer, producer, or special effects specialist, they usually choose a particular style for a character based on the following factors:

  • Uniqueness: In particular, in visually controlled media such as films and television, a protective style can only be chosen because it is different to give viewers a different look at the Star Wars universe than that of it being the same age and the same age.
  • Established tradition: Depending on a character's affiliation, pre-existing traditions or previous work relating to that character may indicate that the character has mastered a certain form. Based on the form that is most likely to be used, they would choose a particular guard to match that form (there are several guards per form that vary and both in the real chronology of the media as well as are quite inconsistent within the Star Wars timeline).
  • Situation: The relative size, strength and ability of the opponent; the number The opponent; and the quarters (narrow corridors towards an open battlefield) often influence the guard positions used. It also depends on whether the character is mainly stationary (asserting himself) or moving around the battlefield. Opponents who use ranged weapons such as blasters are usually treated with a completely different lightsaber shape and protective posture than opponents who are used against another opponent with a lightsaber.
  • Dark against light: Dark characters have historically used a greater variety of lightsaber shapes throughout the Star Wars canon. This may not be absolutely true, but it caught my eye while researching this answer. These dark characters take protective positions that appear impractical, vulnerable or deceptive at first glance, but generally develop into very impressive lightsaber fights against their light-sided opponents.

Typical light

Typically dark

A very useful primary source

While you can find lightsaber style and form descriptions scattered far and wide across Star Wars media, one of the few works devoted to proper "world building" is the lightsaber forms themselves, and detailed descriptions of the philosophy and mechanics of each - at least how they were known to the Jedi - is the Jedi Path book. You should read the main text of this book (i.e. the material, not that one will be commented on by those who read the book later read ) as if most of it was written at least hundreds of years before the Battle of Yavin (the events of the original trilogy), if not thousands of years. But the alleged addition of pages over time, as well as the commentaries, bring the book as a whole into the recent history of Ahsoka Tano's time.

Brandon

Also, her fighting style changes alongside her clothes during the Clone Wars series and of course during her most recent appearance on the Rebels series.

Spandan

@Brandon: I haven't seen a lot of rebels, but according to his timeline, Ahsoka should be a master Jedi right?

Brandon

@Spandan: That's right. While technically not a Jedi after leaving the Order, she has shown formidable combat skills on par with any of the Jedi Masters previously seen. For example, how to defeat and disarm two Dark Side Inquisitors and damage one of the strongest Sith Lords of all time!

Burgi

Great answer, I wasn't aware that there are so many styles of fighting.