As with most video games, Street Fighter require a device for Inputs to be made by a player. Like with many other fighting game franchises, Street Fighter was made with the intention of using a joystick with 8 directions and six buttons, preferably next to each other.
Since Street Fighter has always been designed for this specific layout, some features that modern controllers have for game consoles are redundant, such as pressure sensitive analog sitcks.
Types of controllers
Because of the many Street Fighter games being ported to various different consoles, as well as various enthusiast-level players and companies making their own throughout the years themselves as well, many types of input devices are available.
Controller
These are among the most common input devices as they usually come with the console that the game itself is being played on. They tend to be cheaper in terms of pricing than most specialized controllers, and have higher applicability with different game genres. These are not as common in Street Fighter due to their layouts, as modern controllers only have four buttons near each other and they tend to not be in the same formation as in arcades. Furthermore, players have to reach to the triggers for the remaining attacks. While this is rectified somewhat by customizable controllers, players do not have "easy access" to all their buttons. Some players also report hands hurting when playing some execution heavy characters. Some players do notably go to gaming events using default controllers that come with the systems.
Touch Screen
These tend to be more common for mobile ports of the games. Modern handheld consoles such as the PlayStation Vita and Nintendo 3DS also have touch screens beside their physical buttons. Players tend to use the touch screen for easy one-button specials and that they can usually bypass usage requirements such as Guile's Sonic Boom not needing a charge.
Keyboard
An option mostly for the PC ports, keyboards are an option for players of said ports. When using a keyboard, it is recommended to use specified gaming keyboards (usually mechanical but membrane or even hybrid keyboards exist) that has "anti-ghosting" features. This allows for more key presses that are useful for doing some actions such as EX Specials. With normal run of the mil keyboards, there tends to be a key limit that prohibits simple gameplay options such as back throws.
Gamepad
Gamepads are designed to be a sort of hybrid for both standard controllers and arcade sticks. These tend to have a single digital pad (D-pad) that can be toggled to control (albeit very limitedly) all movement options to modern consoles. The D-pad does not recognize in-between pressure in movement as Street Fighter and most fighting games do not recognize it themselves. These controllers tend to imitate the arcade layout in that all buttons are aligned in a formation of three in order to simulate the LP MP HP layout for the top and the LK MK HK layout for the bottom. These controllers tend to not be compatible with most other game genres in terms of functionality, as while they do work, they tend to lack the features required.
Arcade Stick
Arcade Sticks are considered to be the "default" controller. While they can be pricey, they emulate the intended playstyle. Starting with Street Fighter IV, these controllers could be more easily modified due to the way manufacturers created them. This can be a desired trait when traveling to fighting game events in order to reduce confusion, as owners can change the artwork and buttons to resemble the original aesthetic as much as they want to. Alongside the buttons themselves, the gate under the joystick is usually either a "square" or "octagonal" gate. Square gates are usually accepted to be better for charge-style characters such as Guile and Vega while octagonal gates is recommended for either input characters such as Ryu and Ken or execution heavy characters such as Ibuki, with Ibuki herself having many Special and Unique Attacks that is most suitable for the octagonal gates and in addition to this, not having a precise input can make an unintended attack come out.
Hitbox
Hitbox controllers[1] are a more recent addition, enabled by the input shortcuts of more modern games, they replace the joystick on the left side of the controller with buttons that are very similar to the attack inputs on the right side. The jump button is positioned in between the left, down, up, and the attack buttons that makes jump available to both the thumbs of the player. This controller has gained controversy in older games due to techniques such as being able to charge Guile's Sonic Boom while walking forward, or the faster ability than most other controllers to side switch on blocking to more easily block Cross-ups, some events do not allow this style of controller.