Basic Spy Strategy
The Spy is a master of deceit and excels at punishing mistakes made by other teams. He's a good choice for covert operations behind enemy lines, but he isn't suited to direct combat compared to other classes due to his fragility combined with his weapons, which are weaker compared to other weapons in head-to-head fights. His ability to cloak and disguise himself allows him to slip past enemy lines undetected, where he can wreak havoc. He can sneak up on targets from behind and backstab them to instantly kill them, or place Sappers on Engineer buildings to disrupt enemy defenses. Moreover, he can see enemy health to determine if an enemy is vulnerable enough to be picked off by his Revolver. However, because of the fear he causes, they often Spy-check their teammates for any potential Spies. Despite his ability to hide and blend in, the Spy can be easily revealed through various means, such as through a Pyro's flames or through the Fishwhacker's bleed. Through cunning and deception, a competent Spy can wreak havoc behind enemy lines and take down important targets in one swing of a Knife.
The Revolver, while weaker compared to some other classes' primary weapons, is accurate and deals decent damage at medium range, and three well-placed shots are enough to take down most classes. It is a good all-around option like all stock weapons and gives the Spy a self-defense weapon in case he gets caught out, a way to deal with targets that are out of reach of the Spy's Knife, a way to deal with targets that cannot be backstabbed or where backstabs would be too risky.
The Tranquilizer Gun, sometimes referred to as the Tranq is an option that switches bullets out for a single dart, which causes enemies hit with it to become colorblind, slower, their ranged damage reduced, and for all melee damage, including the Spy's own Knife to become a Critical hit. The projectile can be difficult to connect, especially as the Tranq only has one shot, but it is a good option for Spies that want to help out their team by weakening enemies or to take out a single target in a melee hit if the target is good at hiding their back.
The Sapper instantly disables an Engineer's Building when placed, causing gradual damage until it is destroyed and can only be removed by the Engineer's Wrench. To effectively neutralize an Engineer's setup, a Spy is advised to first backstab the Engineer, then quickly sap any nearby Sentry Guns to prevent them from targeting and killing the Spy, and then the other Buildings. A Spy can also speed up a building's destruction by attacking it, though your weapons deal reduced damage to sapped buildings, referred to as "sapper armor". If backstabbing isn't possible, a Spy can coordinate with his team to sap the Engineer's buildings, leaving him vulnerable to the Spy's team's assault. In a one-on-one encounter, a Spy player should remember that they have an unlimited supply of Sappers and can place them faster than any Engineer can remove them. Use the window when the Sentry is disabled to engage the Engineer, as he'll likely target you directly before removing the Sapper.
The Knife is integral to Spy's game plan. The Knife allows Spy to instantly take down any class, no matter what health they have in one backstab. The Knife is best used for backstabs but is a pitiful melee weapon otherwise. The Spy has tools such as cloak and his disguses which allow him to position himself behind enemy lines for a backstab. If a backstab is unsuccessful, he always has his Revolver for self-defense.
The Disguise Kit, is one of Spy's essential tools for infiltration and allows him to assume the appearance of an enemy or ally. When close to teammates, disguising as an enemy Spy or another friendly class can reduce suspicion. However, choosing a new disguise produces a brief team-colored smoke effect around the Spy, so it's wise to disguise behind cover or while cloaked. Disgusing takes 2 seconds, so avoid approaching the enemy until the change is complete. While operating behind enemy lines, try to act like like an enemy, for example heading towards objectives they must capture. Be careful of selecting disguise appropriate for the situation; an out-of-place Sniper charging into the enemy or an Engineer not building can arouse suspicion. Reloading while disguised causes's the Spy's disguise to reload as well, which can make the act more convincing. Using the previous disguise key (default B) changes the disguise's weapon to the Spy's current weapon, which can also make the act more convincing. Keep distance from enemies, as bumping into them exposes you as a Spy. Remember that disguises aren't foolproof, and players often randomly spy-check their teammates. Attacking breaks the disguise, so seek a safe spot to re-disguise after escaping.
The Invis Watch is the other main infiltration tool for the Spy, but instead of allowing a Spy to hide in plain sight, the Invis Watch allows him to hide out of sight. The Invis Watch allows a Spy to turn invisible and has the quietest decloak sound of all the watches. However, it's cloak is only 10 seconds long, and cloaking for longer causes the Spy to become visible. While invisible the Spy gains 20% damage resistance, but this does not make the Spy invincible. To have cloak ready when needed, decloak in safe places and pick up Ammo packs to refill the cloak meter. Be careful though; Ammo packs vanishing into thin air can alert enemy players who may spy-check the place. While in enemy territory, stay on the move to reduce your chance's of getting caught.
The L'escampetter is a watch that trades longer cloak duration for even quicker movement. Cloaking with L'escampette kicks the Spy up to 130% of his default running speed, but the cloak drains twice as fast; getting hurt while cloaked will drain it even faster, and it has a more distinct cloaking sound compared to the Invis Watch. Use this when you need to quickly get behind enemy lines, but be sure to plan a route to avoid as much damage as possible because of the cloak drain on hit,a dn be sure to de-cloak somewhere to not alert enemies.