Slender

Slender: The Eight Pages is set in the middle of a forest during the night and is played from a first person perspective. The player's objective is to collect eight pages located in various areas of the forest while avoiding the Slender Man. Slender Man moves by teleporting. The player is equipped with only a flashlight to see through the dark; its battery life is limited and will eventually shut down permanently if left on for an extended period of time. The player character has the ability to jog, which will tire out the player and make him wheeze if jogging for too long. Slender Man occasionally appears in the player's field of vision, accompanied with loud piano slamming noises and/or static on the screen. This also results in the ability to sprint for a short period of time. Sprinting allows the player to move faster than jogging, but doing so will decrease the maximum stamina available for jogging and sprinting. A game over occurs when either the player has taken too long to find a note, the player stares at Slender Man for too long, or if Slender Man comes into contact with the player, which will turn them around and end the game. The game over screen shows Slender Man's 'face' up close and blinking static pulses. As the player collects pages, the fog in the forest grows thicker and Slender Man appears closer to the player character, though the sprinting speed slowly increases as well.

Even if the player's character successfully collects all the eight pages, the Slender Man will continue to chase them. Once all the pages are collected, one is allowed to walk around for a couple of seconds in silence until it appears behind the player and ends the game. However, the end credits can be viewed afterwards if all eight pages were successfully collected, and new game modes are then unlocked. There is also a "grace period" in the very beginning of the game, during which Slender Man remains inactive for a few minutes or until the player collects the first page. However, the difficulty level increases the longer one goes without collecting pages. The end of this grace period is indicated by a repetitive stomping sound echoing in the background (also activated by collecting the first page). This sound is heard throughout the rest of the game & gradually gets quicker as more pages are collected, as well as several other layering sounds. These sounds include a low droning sound (pages 3–4), a loud wind (pages 5–6), and then a mysterious and unnerving beeping sound (page 7). Only once all 8 pages are collected, the sounds abruptly fade into silence.

In Version 0.9.4 there is a "Daytime Mode" that can be unlocked. To unlock this mode, the player must beat the game as normal, but there is a different ending where the player awakes in the daytime after collecting all eight pages and being caught by Slender Man. After waking up, the player can walk around in the daytime for a few seconds before the credits roll. "Daytime Mode" is simply during the day and without a flashlight. If the player beats "Daytime Mode" the ending will be the same as before, only the player wakes up at night. After the credits roll, the player will have unlocked "$20 Mode". In this mode, gameplay is the same as normal mode, except that if the player sees Slender Man a song called "20 Dollars" by American rap artist Ron Browz starts playing. This is a reference to a fan-originated meme about Slender Man, stating that if a person gives Slender Man 20 dollars, he will leave the person alone. This is the only version in which the player selects these modes in the "Options" portion of the menu screen, and this is also the only version in which two hidden modes can be played at once ("Daytime Mode" and "$20 Mode"). There is also a "MH (Marble Hornets) mode", viewing the gameplay as a 'Marble Hornets' entry. The creepy sounds and page collector has been removed, there are static bars on the edges, and the ending is a bit different. However, the "$20 Mode" was removed in version 0.9.7 due to a copyright issue.

From version 0.9.7 on there is ambience during the menu screen, as well as portions of the eight pages being shown. There are now links to the Slender Man mythos forums and some popular web series based on the mythos such as 'Marble Hornets' and 'TribeTwelve'. As of this version, the game was officially renamed Slender: The Eight Pages to avoid confusion with future versions such as 'Slender: The Arrival'. "$20 Mode" has been removed due to the copyrighted material. "MH Mode" has been renamed to "Marble Hornets Mode" (simply the unabbreviated version of the title). Two new light sources are available: a glow stick with almost no light with almost no range at all, and a crank lantern with a wide range but short amount of light which must be replenished by cranking the lantern. The player can now pause the game by pressing escape, but only when there is no static on the screen as to not allow the player to quit in response to being frightened.