How to lane against Viper?

If you are in a 1v1 situation with Viper you're probably not going to win. The trick to killing Viper is to gank him and have the numbers advantage, otherwise you're going to get kited to death. The threat of Viper is early, where he is one of the strongest laners but has no way to escape dangerous situations.

He's very difficult to lane against because he can spam Poison Attack on you without drawing creep aggro, and the lower your HP gets the more damage it will do. Make sure you take plenty of regen to lane, and don't be afraid to courier in more - just make sure you keep yourself at full or nearly full HP. Focus on not feeding him kills, and get your farm/last hits when you can do so safely. If you're playing with other players, wait until the lane is pushing towards your tower and then have someone with good lock-down rotate and help you gank him.

Strategy:

This might sound crazy, but against a mid Viper it is reasonable to have a lane of two other heroes. Viper doesn't have any AoE attacks and his attacks hurt less the higher your HP is, so having two people against him is very reasonable. The higher your HP is, the less he hurts you, so don't hesitate to keep your health topped up.

Items

Linken's Sphere is great because it blocks Viper's ult and its cooldown is shorter than his  Viper Strike's. That means that if you two are 1v1ing then after you buy it his Viper Strike is permanently wasted.

Heroes:

Outfight Viper with

• Gyrocopter: Burst damage and a little bit of stun. You're also faster than Viper at the outset, so he can't run very easily.
• Weaver: With Shukuchi  and bugs for harassment and your ult to stay alive you can take Viper 1v1.

Out-Harass Viper with

Sniper, Silencer, or Phantom Lancer, if you can rely on yourself not to overextend. For Sniper skilling  Take Aim early you will outrange Viper. Phantom Lancer has a nice harassing nuke and an escape. Silencer:  Curse of the Silent is not cancelled by any of Viper's abilities except his  Viper Strike. These heroes HP pool is small, so you can't take much harass back. They are best against Viper in a 2 v 2 or 2 v 1 situation where you've got someone who can heal you alongside. These heroes can harass Viper very effectively, but require good positioning to do it.

Enchantress: He hits you, he's slowed. You take too much damage? Heal up. Grab some nice jungle creeps and keep in mind that the bastard has no AoE attacks.

Get rune control with

Puck, Queen of Pain, or Tinker. Harass Viper with your spells and also push the wave out enough that you can get to the runes. Get a Bottle, obviously. Viper is one of the slowest heroes, so you can outrace him to the runes. Keep the harassment up, and use Bottle to refill your mana if there's a rune right there even if you already have full health. The added regen should help you overcome Viper's 1v1 advantages.

Gank Viper with

Lycanthrope, Naga Siren, Razor, and Outworld Devourer are all great heroes to have on your team vs. Viper though not necessarily laned against him. Razor or Outworld Devourer do alright vs. Viper in lane, but  Corrosive Skin is a real pain for them. However, if they're rotating over from another lane to gank him they can wreck Viper's day. Outworld Devourer can keep him from running, and Razor can neuter Viper's right-click damage. Lycanthrope and Naga Siren both take advantage of Viper's lack of AoE attacks. Lycanthrope's ult makes him immune to slows, and  Naga Siren can net Viper as well as escape with her song if necessary.

Lich: You can deny extra well, slow Viper(whose orb attacks are his bread and butter), and armor yourself and your pals against him. The armor doesn't slow him, and you don't have a lot of killing power, but you should contribute a lot to fights against him.