sans.

Snowdin Forest is the second region the protagonist encounters in the Underground. It is seen after the protagonist defeats Toriel and receives judgment from Flowey in the Ruins. For the area's puzzles, see Snowdin/Puzzles. Papyrus and Sans are the first characters to make their debut, and they host many of the puzzles the protagonist encounters. The Mysterious Door can be found in this region, along with a hidden enemy called Glyde. The "Snowdin Canine Unit" resides here, making this region the most concentrated area of Royal Guard members in the Underground. The protagonist can find the Tough Glove in a box and can purchase the Manly Bandanna from the Snowdin Shopkeeper. The final enemy of this region is Greater Dog. After passing them, the protagonist encounters Papyrus and Sans for the last time before reaching Snowdin Town. After confronting Toriel and leaving the Ruins, the protagonist meets Sans and Papyrus in Snowdin Forest. Sans jokes with them, and Papyrus attempts to jape them with puzzles. The protagonist encounters the members of the Snowdin Canine Unit of the Royal Guard as they make their way to Snowdin Town. They can also accept a snowman's offer to take a Snowman Piece with them on their journey.[1] The protagonist is Nice Cream Guy's first customer, and they give him hope for his business.[2] Once the protagonist passes the Gauntlet of Deadly Terror, they enter Snowdin Town. Coniferous trees, snowfields, and small cave systems populate Snowdin Forest, and this region has many characteristics of a taiga biome. It also includes a large river that flows east; Ice Wolf uses this river to transport ice to the CORE. Snow blankets the ground throughout Snowdin Forest and Snowdin Town. The first room of Snowdin Forest is long and horizontal, and coniferous trees provide a constant background. As the protagonist walks to the right, coniferous trees freckle the foreground, allowing Sans to appear as a silhouette between them as he follows the protagonist. A sturdy branch blocks a part of the path and, as the protagonist passes by it, the branch splinters.[7] After his introduction, Sans informs the protagonist that his brother constructed the wooden bridge.[8] After crossing the bridge, the protagonist hides behind a conveniently-shaped lamp, which is located next to Sans's sentry station[9] and a couple rocks. This area serves as Papyrus's first appearance as the brothers talk to one another.

The right end of the first room connects to the "Box Road", which has a SAVE Point and a box that contains the Tough Glove. The north exit of this room connects to the river with a fishing rod holding a note underwater. The right exit leads to the next encounter with Sans and the protagonist's first encounter with Papyrus. The horizontal room that features the encounter with Sans and Papyrus also houses Papyrus's cardboard sentry station[10] near the east exit. This exit leads to a short horizontal room that contains Doggo's sentry station and the first canine mini-boss battle, in which Doggo introduces blue attacks. There are dog treats to the right of Doggo's station. After going through the east exit, the protagonist encounters Sans and a patch of ice that they can slide on. A sign in the middle of the ice reads that ice is in all directions and that Snowdin Town is to the east. To the north of the ice room, a snowman offers the protagonist a piece of himself to take with them on their travels. The east exit of the ice room leads to the Invisible Electricity Maze, hosted by Sans and Papyrus. This small room connects to a larger room that has the Nice Cream Guy, who sells Nice Cream, the snowdecahedron, as well as the Ball Game. The exit in the top right of this room leads to the sentry stations of the Dogi, and also includes a sign that explains "smell danger ratings."[11] The bottom right exit of the large room leads to another encounter with Sans and Papyrus. A word search lies on the ground, provided by Sans.[12] The east exit of this small room leads to the "Spaghetti" room, which contains a SAVE Point, a note from Papyrus,[13] frozen spaghetti that is stuck to the table it is on,[14] and a microwave. The microwave and spaghetti are on separate tables. A wall to the north has a mouse hole and, atop this ledge, there appears to be frozen flowers. On the True Pacifist Route, the dialog of the table changes.[15] The east exit of the "Spaghetti" room leads to a large room whose exit is blocked by spikes. At the bottom left of the room, there is a map covered in snow that the protagonist can reveal by walking over it. The switch to retract the spikes is located between two coniferous trees in the upper right of the room. After passing the retracted spikes, the protagonist encounters the Dogi. Once the Dogi are defeated, the protagonist can leave the large room through the south exit and complete the first XOXO puzzle. Once completed, spikes near the east exit of the room retract, and Papyrus questions the protagonist about the state of his spaghetti trap.[16] After leaving through the east exit, the protagonist encounters the second XOXO puzzle that Papyrus supervises because he modified the puzzle while he was waiting.[17] Again, spikes prevent the protagonist from leaving the room through the east exit until they complete the puzzle. The next room hosts the first instance of the Multicolor Tile Puzzle, which has a console that looks strikingly similar to Mettaton. Both Sans and Papyrus look on as the machine creates a simple "puzzle" for the protagonist to solve; Papyrus spins out of the room without saying a word.

If the protagonist asks Papyrus to repeat the rules for the Multicolor Tile Puzzle multiple times, he becomes confused and tells the protagonist to try the puzzle on their own. Papyrus leaves illegible instructions[18] and walks offscreen. Leaving the Tile Puzzle room through the east exit leads to the "Dog House" room, which contains Lesser Dog's station and, depending on the protagonist's actions during Lesser Dog's encounter, various degrees of snow sculptures. If the protagonist killed Lesser Dog, the statues are replaced with a pile of mushy snow. The east exit of this room leads to the third and final XOXO puzzle, which the protagonist has to slide on ice to solve. Falling off of the edge of this puzzle causes the protagonist to leave this room and appear in a room directly south of the XOXO puzzle. This room contains a snow Papyrus and a lump of snow with Sans's name written on it. The north exit of this room leads back to the XOXO puzzle. A bridge that leads to the east exit of the room forms after the protagonist completes the puzzle, and they can slide through a tunnel of coniferous trees to get to the next area. Directly south of the bridge is an area where the protagonist encounters Gyftrot and where the Mysterious Door is located. Backtracking to the ice bridge's exit, if the protagonist travels east, they encounter a room full of snow poffs. If every snow poff is inspected and interacted with, the protagonist receives 30G. This room also contains the small doghouse of Greater Dog. Near the east exit, Greater Dog's encounter with the protagonist occurs after they rise out of the snow disguised as a snow poff. After defeating Greater Dog, the protagonist can leave the room through the east exit and approach the last puzzle, The Gauntlet of Deadly Terror. Papyrus threatens to activate the Gauntlet but ultimately decides not to.[19]

After crossing over the long bridge, the protagonist leaves Snowdin Forest and enters Snowdin Town.

The forest section overseen in the background by the bridge is inaccessible to the protagonist.