You'll emerge into a dark and snowy forest. Follow the path east, and you'll be greeted by Sans the skeleton. After introducing himself he'll take you to meet his brother, Papyrus.
After their somewhat eccentric conversation you can optionally speak to Sans for some more exposition, then head further east.
In the next area there's a save point and a Dimensional Box - these are scattered around the map and allow you to store unwanted items.
Put your Donut in there for safekeeping, then keep moving east.
Keep moving east and you'll run into Sans and Papyrus again, and then a bit further on you'll come to a sentry post manned by Doggo.
Doggo boss fight
Doggo introduces a new attack mechanic - his blue attacks won't harm you if you keep still when they hit you. Avoid the snow attacks, and when he swings his blue sword keep still and they'll pass straight through you. After his first blue attack Pet him, and then you can Spare him.
Keep moving east and Sans will give you a slightly-too-late and not entirely helpful explanation of blue attacks. Head north and speak to the snowman and he'll give you a piece of himself to carry.
This is a non-essential plot item, but can also be used to heal yourself - if you need to use it, come back and speak to the snowman again and he'll give you a replacement.
Keep travelling east and you'll meet Papyrus again. His puzzle doesn't quite work out as he'd hoped, and he'll run off. Follow him, and cross the bridge in the next area.
There's a snowball in the clear area and a hole at the bottom, and pushing the snowball into the hole will earn you between 2G and 50G depending on how quickly and/or accurately you do it, but it's entirely optional.
Leave the area through the exit in the south east, and you'll come across another unsuccessful attempt by Papyrus to halt your progress.
When asked which puzzle you find hardest the skeletal brothers will both be happier if you pick Junior Jumble, but it has no effect on the outcome of anything.
The next area to the east just has a save point in it, so save and keep moving.
In the next area there's a hidden switch in the patch with no snow in the top right corner - use it to clear the route across the bridge in the south east.
Dogi boss fight and snowball puzzle solution
Avoid their axes by moving to the bottom centre of the box, then moving beneath them either to the left or right when they bring their axes together, and when two smaller dogs appear and spit out white and blue hearts move to the top of the box and squeeze between the hearts as they approach.
Roll in the Dirt, then have one of them Re-Smell you, and then Pet them each once before Sparing them.
The next area has a simple puzzle that involves stepping on each X on the ground to change it to an O before hitting the switch.
They're all in a straight line, so just walk east, hit the switch, and then move through the exit - Papyrus has prepared a more complex puzzle here. You can either solve it or fail a few times to have him help.
In the next area there's another puzzle and Papyrus will explain the extraordinarily complicated rules to you then ask if you understand them.
Whichever option you take you avoid any problems: if you say yes he'll switch the puzzle on but due to poor planning on his part he's arranged the puzzle with a clear path all the way through, and if you ask him to explain the rules again a couple of times he'll just give up and leave without activating it.
Save in the next area, then keep going east to find the first puzzle you actually have to solve. Once it's complete keep moving east, and head south to a dead end area with a mysterious door...
Snowdin mysterious door
As you explore Snowdin, towards the end you'll come to a mysterious door inside a cliff. The only way to open it is to complete a Pacifist walkthrough - if you are following this guide, then hopefully you should be on the way to doing so - and when it comes to the Kickstarter backer credits, you must successfully dodge every single name.
Doing so will open the door, resulting in a few Easter Eggs and secrets. The following video from Hawelo92 shows how it's done and what's inside - of course, we'd recommend you attempt it yourself before watching.
Either way, if this is your first time seeing the door, it cannot be opened right now. So continue eastwards, and at the far end of the next area you'll encounter Greater Dog.
Playing Undertale? Our complete Undertale walkthrough and Pacifist guide will explain how to finish the game while sparing everyone, covering all areas including the Ruins, Snowdin, Waterfall, Hotlands and The Core and more. You can also learn about how to unlock every Undertale ending and all Undertale Trophies, access hard mode and play the game in the most evil way possible with a Genocide run.
Greater Dog boss fight
His bark attack is fast moving and there isn't really anywhere safe to hide which means skill is your only real option here, and his spear attack will randomly change from white to blue so be sure to stop moving when required.
In order to Spare him you'll need to Beckon him, Pet him, Play with him, then Pet him twice more.
Once he's defeated, head east for Papyrus's last puzzle which is even less successful than his previous attempts. Cross the bridge, and you'll find yourself in civilisation!
There's a lot of background information and flavour text to be had by talking to the characters in town and visiting the library, you can rest at the inn for free which will temporarily increase your HP beyond its maximum, and the shop sells a bandanna which increases your defence.
When you've explored, leave town to the east where you'll run into Papyrus - he'll start off wanting to be friends, but will soon change his mind, triggering the Papyrus boss fight.
Again, we'll be tackling it as part of a Pacifist playthrough, if you're aiming for that too.