Spy checking

A BLU Pyro (left) Spy-checks teammates leaving their spawn area on Harvest, revealing a Spy (right) disguised as the Demoman (middle) next to him.

“

Hard ta stab a guy in da back when he's beatin' ya freakin' head in, huh?

Click to listen

— The Scout on anti-espionage.

”

Spy checking is a common term for the investigations players make to determine where or who enemy Spies are and eliminate them. These investigations are both useful and important because Spies can instantly kill by attacking from behind. The process can be somewhat complicated because disguised Spies can use the Dead Ringer to make a hasty escape when discovered, or avoid taking fire damage by equipping the Spy-cicle.

Identifying Spies

General Strategy

The easiest and most common way to Spy-check is to simply shoot a teammate. Real teammates take no damage at all, while enemy Spies die after a few shots. Pyros excel at this method, as their Flame Thrower can Spy-check multiple teammates at once and will ignite a Spy, instantly ruining his disguise.

Remember that players on opposing teams cannot pass through each other. Bumping into a teammate indicates that that player is an enemy Spy.

Look for teammates that are behaving suspiciously. Players in unusual positions, moving in the wrong direction, deliberately avoiding contact with teammates, or hiding in corners should all be Spy checked.

Pay special attention to areas with health kits or ammo boxes or corners, nooks, and spots that players usually do not enter. Spies tend to use these areas to hide in while they recharge their Cloak and Dagger.

Watch for teammates who are not firing their weapons. Spies cannot fire their weapon without removing their disguise. They can pretend to reload their weapons, keep in mind a Spy can switch weapons at the near-end of the reload animation to continuously appear to reload.

Keep an eye out for smoke surrounding players. When a Spy uses the Disguise Kit, it takes a moment for the disguise to activate, during which the Spy will be shrouded in team-colored smoke. Spies can change their disguise much faster than they can apply a new one, however.

If you are dead, you can cycle through different camera angles around the map while waiting to respawn. Look out behind teammates or on open points for Spies uncloaking or disguising. You can then alert teammates or Spy-check where you last saw the Spy when you respawn.

For the first few seconds after you respawn, you can see silhouettes of your teammates. If you see one appear from nowhere, it may be an enemy Spy decloaking.

If a friendly player is trying to get behind you for no reason, they may be attempting to backstab you. If a player is acting suspiciously, never turn your back on them.

Spies disguised as a Spy will always have the disguise mask on.

Class-specific strategies

Scout

The Scout is the fastest class. Because of this, one effective strategy is to run around the map and try to bump into fellow teammates. As noted above, any teammate that you cannot pass through is an enemy Spy in disguise.
Some of the Scout's melee weapons can be used to Spy-check effectively. Refer to these and their individual articles for details.
Mad Milk will reveal disguised and cloaked Spies, since a coated Spy will be visible by white drips.
The Boston Basher, Flying Guillotine, and Wrap Assassin bauble will cause enemies to bleed when struck. If you hit a teammate and they begin to bleed, you have discovered an enemy Spy. Be warned that with the Boston Basher you will take damage and start bleeding if you miss, so trying to find a cloaked Spy with the Boston Basher is unwise.
The Fan O'War can also mark enemies for death. If you suspect a teammate of being a Spy, and cause a skull and crossbones to appear over them, you have just marked an enemy Spy.

Soldier

The Soldier has few particular Spy-check strategies apart from the general ones. Spy-checking by simply shooting rockets at suspicious players is very effective because of the high damage your rockets do at close range. However, disguised enemy Spies will not receive damage knockback from your rockets.

When you activate a banner, nearby teammates that do not emit a glow are Spies.
- Shooting a disguised Spy will charge a banner's rage meter.
- The Disciplinary Action will still apply a speed boost, regardless of if the player whipped is a disguised Spy.

Pyro

The Pyro's ability to set enemies on fire with incendiary weapons is perhaps the most useful tool for detecting Spies, since only enemies can be ignited. This is the most reliable method of Spy checking teammates. The team-colored glow produced by a burning player is especially visible when surrounding a cloaked or disguised Spy. It is recommended to use only small bursts to Spy check to conserve Flame Thrower ammunition.
The Compression blast is also useful in revealing Spies, as well as stopping attempts to escape. Teammates will not be affected by compression blast, so any teammate that can be pushed by it is a Spy. While flames are normally more efficient, compression blasts can be used to push Spies away from your teammates if they are in danger of being backstabbed.
If a Spy is using the Dead Ringer, they may appear to die instantly from your flames, though the flames will tend to surround them for a little while afterwards, which can show you that they faked their death. Spray fire in the vicinity to try and reignite them, and if you find them, pursue them until they die for real.
Know that the Spy-cicle greatly aids Spies trying to escape or stay hidden. Be aware of its use and counter it with other weapons if necessary.
- The noise a Spy-cicle makes when extinguishing flames is very distinct. Learn to recognize it, both when the Spy is cloaked and when they are disguised as a teammate.

Demoman

Placing Stickybombs over a wide area can cause Spies to hesitate about traversing such minefields. Teammates have no such qualms, and simply walk across these areas.
Planting a cluster of Stickybombs in an Engineer nest helps to deter the buildings from getting sapped by the Spy. If your Engineers happen to yell out that they are getting sapped, detonate the Stickybombs to catch the Spy red-handed.

Heavy

Because movement speed is greatly reduced for a spun-up Heavy, they are tempting backstab targets. This can sometimes be used as a lure to goad enemy Spies to approach. Act unaware, then turn around to surprise a possible Spy.
As Heavies are often coupled with Medics, Spies place great priority upon stabbing the Medic first, then the Heavy, to deny the team the Medic's support. Turn around quickly if you hear your Medic die from a backstab.
Spy-check by focusing your Minigun fire on a teammate. Spies will often die in a few seconds.

Engineer

Keep an ear out for Sapper notifications; if a teammate is standing near the sapped building, that teammate is probably a Spy.
Spy-check suspicious players that approach your buildings with your secondary weapon. Your primary weapon can also be used, but its ammo is often needed for other threats. Avoid chasing the Spy with your Wrench, as it leaves your buildings vulnerable. The Wrench is also bad for Spy-checking since it prioritizes repairs over combat, meaning that buildings will always be hit instead of players next to them.
If any teammate is unable to pass through a Sentry Gun or Dispenser, that teammate is a Spy. Placing these buildings in narrow passages and checking them regularly can severely slow a Spy’s forward progress.
The Southern Hospitality is a good weapon for spychecking thanks to its bleed attribute.

Medic

As a Medic, Spies can use you to gain health while disguised. If you are particularly suspicious of a player, do not heal them. Spy-check them with your melee weapon or have your patient deal with them for you.
Spies may target you while you are healing a patient. Watch your back while healing. You can also have your patient Spy-check for you, though this may be difficult during intense battles. Your Medi Gun stays locked onto your patient even if you turn away, so check for your team and call out any potential Spies during firefights.
Spies may also simply head directly for your patient rather than yourself. If a teammate seems to approaching your patient's back, warn them of a possible Spy.
Avoid chasing Spies too much — your ability to heal is generally more useful. Spies can also lure you into a backstab, so be careful. Your patient is generally more suited to killing the Spy than you are.
Keep your back to the wall. While not exactly a Spy checking strategy, keeping your back to the wall can be important as a Medic because it makes it harder for Spies to sneak up on you (instead of having to check 360 degrees around you, you only have to check 180 in front of you).
When shooting at damaged teammates with the Crusader's Crossbow, listen for the sounds it makes when it hits a teammate. Disguised Spies will make a distinct meat impact sound when hit.

Sniper

Some Snipers are oblivious to their surroundings while zoomed in. Listen carefully, and check the area you are in after firing a shot.
Switch positions frequently and check your surroundings as you do so — newly-respawned Spies will sometimes head for where they last saw you, especially if you have recently killed them.
Jarate is a particularly useful Spy-check weapon, as it reveals both cloaked and disguised Spies. Use it to Spy-check suspicious teammates.
- Equipping the Bushwacka allows you to kill a Jarate-soaked Spy instantly. Spies who understand this will often retreat if you hit them with Jarate, allowing you to follow up with a Sniper Rifle shot. Be careful — they may try to take advantage of your damage vulnerability by gunning you down with their Revolver — if you are low on health, consider retreating to heal before confronting the Spy.
The Razorback will prevent a Spy from backstabbing you, but doesn't protect you from being shot! Be careful when separated from your team, even with its protection.

Spy

Spies are generally poor Spy-checkers, because they deal poor ranged damage and use tools to escape quickly. Although their backstab is very useful to protect teammates as it kills instantly, Spies spend their time best among the enemy and rarely encounter one another.

If you stand behind a teammate while holding your knife and it raises in the ‘backstab’ position, you have discovered an enemy Spy. Backstabbing a Spy is a guaranteed kill — not even the Dead Ringer can save them from a backstab.

Revealing cloaked Spies

When cloaked, Spies will momentarily appear as a team-colored silhouette upon being damaged or when bumping into enemy players. Keep an eye out for when a Spy is revealed this way. Strafing left and right while navigating corridors makes it difficult for a cloaked Spy to pass you safely.
- Note that The Dead Ringer greatly diminishes this drawback, as they can use it to escape easily.

Shooting into common Spy hiding places may reveal an unlucky Spy.

Try to listen for the sounds Spies make while cloaking and decloaking. If you hear a characteristic cloaking sound, a Spy is nearby. Remember that friendly Spies make this sound as well.

An ammo box or health pack that disappears without a player picking it up indicates that it was picked up by a cloaked Spy. Spy-check nearby to reveal any careless Spies.

In places with water, look for floating water drops. Players climbing out of water will be visibly dripping with it, including cloaked Spies.

An automatic door that suddenly opens without any visible player being nearby indicates a cloaked Spy passing through.

Protecting an Engineer's buildings

Since an Engineer's buildings are a major target for Spies, specific strategies may be more effective around Engineer's buildings:

Spy-check suspicious players that approach a friendly Engineer's buildings. Spies trying to sap buildings often run straight towards them. You can body-block Spies to prevent them from placing a Sapper.

As a Pyro, use Dispensers to constantly refill the ammo of your Flame Thrower. You can use this ammo to create a constant firewall that Spies cannot safely pass through or to constantly Spy-check the area. Heavies can also make use of Dispensers in this way.

As a Demoman, Stickybombs can be placed around friendly buildings to kill Spies who try to sap them. Place a few bombs around an Engineer's buildings and detonate them when you hear the Engineer announce that his buildings are being sapped. Watch your stickybomb counter, though — if the number begins to decrease, an enemy is destroying them.

As an Engineer, if a Teleporter is being sapped from its entrance, you can Spy-check the next player teleporting through once you remove the Sapper. This may be an enemy Spy trying to telefrag you, so be careful not to stand on top of it. Turning the telefrag attempt into your own surprise can frustrate enemy Spies.

Identifying enemy Spies

Various team-colored indicators definitively determine an enemy Spy or a friendly one, including:
- The flicker a cloaked Spy makes when being bumped or injured.
- The fading a cloaked Spy does while cloaking or uncloaking.
- The glow a player on fire makes.
- The smoke from a recent use of the Disguise Kit.

Signs that definitely indicate an enemy Spy, or lack thereof

Common signs

A 'teammate' that cannot pass through another teammate, or conversely, a 'teammate' that has been observed walking through an enemy.
A 'teammate' that asks for Medic and has the "wrong" cross background colour. For example, a Pyro at full health having its background red like on heavily injured teammates, or a near-dead Heavy having it white.
A 'teammate' who cannot enter areas open to your team (such as supply rooms), or conversely can enter areas forbidden to your team.
A 'teammate' placing Sappers on friendly buildings.
A 'teammate' standing on a friendly Sentry Gun or Dispenser, or who cannot pass through them, and is not the Engineer who owns the building.
Two people that have the same name. One (or both) of them is a Spy.
Seeing or hearing a voice command attributed to yourself without you having used it, or more importantly, seeing "yourself" moving around.
A 'teammate' that is known to be dead or elsewhere.
A 'teammate' who has a name that does not correspond with their current class on the scoreboard. This happens when a Spy disguises as a class not currently on the team, or if the person has changed class while the Spy was disguised. Their disguise will be holding the stock weapon for that slot.
A health or ammo pickup that vanishes without cause; this means a cloaked Spy has stolen it. After a while, ammo pickups dropped by dead players will disappear and it does not mean it's a Spy picking them up.
A 'teammate' on an uncontested control point or near the cart on Payload maps who does not seem to be capturing the point or pushing the cart (assuming the point is available for capture by that team).
A non-Spy 'teammate' that is being ignored by an enemy Sentry Gun.
A non-Spy 'teammate' that is being healed by an enemy Medic or Dispenser.
A non-Spy, non-Heavy 'teammate' picking up a health pack at full health.
Due to bugs, a ‘teammate’ either holding a stock weapon while wearing a wearable weapon of that slot (e.g. the Darwin's Danger Shield and the SMG), or holding a weapon without its wearable part (e.g. a Soldier holding a bugle without its backpack).
A ‘teammate’ with parts of their character model missing, such as a Demoman without legs. This is a glitch surrounding Spy’s disguise — occasionally, the disguise will not display properly on enemy players’ computers.
A 'teammate' with an impossible health value. For example, a Scout with 300 health.
A 'teammate' whose name is displaying as an enemy's.

Class- or item-based signs

A Scout running at an average speed while not having the Baby Face Blaster equipped.
A 'teammate' running at normal speed while holding a weapon like the Gloves of Running Urgently or Powerjack.
A 'teammate' having normal class health while having a weapon like the Sandman or Bootlegger equipped
A 'teammate' being soaked by friendly Jarate or Mad Milk, or not being affected by the enemy's.
An Engineer with his Hotrod down despite not carrying a building.
If the Spy is disguised as an Engineer equipped with a Beep Boy, the facial expression on the Beep Boy will always be sad.
A 'teammate' with an incorrectly coloured Grandmaster.
A Spy who does not move at the speed of his disguise.
A Soldier or Demoman whose B.A.S.E. Jumper renders incorrectly as a scrunched-up parachute.
A disguised Spy shot with the Huntsman, Rescue Ranger or Crusader's Crossbow will make the same noise as an enemy being hit.

Signs that suggest an enemy Spy

None of these indicators are conclusive proof of a Spy, but all of them would be a good time to Spy check:

Common signs

A teammate trying to stay behind other teammates, as if trying to backstab them.
A teammate not firing at the enemy.
A teammate who is in the direct firing line of an enemy but is not being fired at.
A teammate who retreats backward upon seeing other teammates, while still facing those teammates.
A teammate who appears to be dodging your team's attacks or backpedals immediately after seeing loose grenades or a carpet of friendly Stickybombs.
A teammate that deliberately avoids walking through other teammates, especially in tight corridors. Spies will strafe and dodge other players to avoid bumping into them.
A teammate with an entirely stock loadout (occurs when a Spy disguises as a class the team does not have).
A teammate being attacked or accused by real teammates who believe the player is a Spy.
A teammate holding their primary weapon for longer than they should. In particular, it is unusual to see Spies, Engineers, Medics, and Demomen holding their primary weapons for long, as they will usually switch to other weapons.
A teammate hanging around areas that are advantageous to Spies, such as dark corners and nooks.
A teammate that isn't displaying the player's usual behavior.
Someone standing still. This could be a Spy trying to line up an Ambassador headshot.
A teammate that appears to be looking more at your team than at the battle. Note that this is normal behaviour for Medics.
Being suddenly blocked for no apparent reason. This may indicate a cloaked Spy passing through.
A teammate suspiciously near Sentry Guns or Teleporter Exits, especially if they are attempting to move behind the Engineer tending them.
A teammate acting inappropriately for their class, such as an Engineer with no nearby buildings or a Sniper near the Intelligence but not scoped in.

Class- or item-based signs

A full health Soldier who doesn’t Rocket Jump to the front lines.
A burning Pyro (only the Gas Passer can burn Pyros for that long).
A full health Demoman who doesn’t Sticky Jump to the front lines.
A Heavy that does not spin his primary weapon, even when enemies appear.
An Engineer that does not appear to be upgrading or repairing buildings.
A Medic without any Übercharge built up.
A Medic who isn't healing anyone.
A Sniper who does not stop to zoom in.
A Spy who is not behind the enemy.
A Spy that ignores targets that were in a prime position to be taken care of, such as not Backstabbing unaware enemies or sapping unattended buildings.
A person you know that is using a weapon that they don't normally use (i.e. a friend who normally uses the Huntsman, but appears as using the stock Sniper Rifle; meaning a Spy is disguised as a Sniper when your team doesn't have any) or not wearing hats if they wear them (again, a Spy disguised as a class your team doesn't have).

A teammate holding an inappropriate weapon, such as a Medic holding (but not firing) a Syringe Gun while there are teammates around.

Signs that indicate a teammate is not an enemy Spy

These actions prove that a teammate is definitely not an enemy Spy. Performing any of these is a good way to inform your teammates that you are not an enemy Spy.

Common signs

Any usage of a weapon or item (taunting, shooting, swinging, scoping, eating, drinking, etc). This does not apply to reloading, however, as Spies are able to imitate a reload by reloading their Revolver whilst disguised. However, they can only pretend to ‘reload’ once — a class with an individual reload weapon out reloading two or more shots is real.
A teammate that passes through other teammates, or yourself, as opposed to being blocked. (However, this can also happen if both ‘teammates’ are enemy Spies).
A teammate entering an area forbidden to the enemy, such as resupply rooms.
A teammate who appears to take damage from enemy fire.
A player who can pass through friendly buildings.
A teammate that is carrying the enemy team's Intelligence or capturing a control point for your team.
A teammate using certain responses which a Spy cannot imitate himself.
A teammate that can be spectated while dead. Note that spectating through the menu moves you to a new team and that a few servers allow spectating enemy players.
In Mann vs. Machine mode, a teammate that jumps. Spy Robots never jump.

Class- or item-based signs

Any usage of class-specific abilities, e.g. Scouts double jumping, Heavies spinning their Minigun, Snipers that are scoped in, etc.
A Scout moving at his normal movement speed.
An Engineer holding the Destruction PDA or a toolbox.
A Medic with any amount of Übercharge built up.
A Spy holding their Sapper. If a Spy disguises as an enemy Spy, the disguise can never hold the Sapper.
A Spy without a disguise on. If a Spy disguises as an enemy Spy, the disguise will always have a disguise on.

Spy-checking Spies with items

Main article: Anti-Spy strategy

Dealing with the Dead Ringer

The Spy has the ability to feign death with one of his unlockable items, the Dead Ringer, so always be wary upon killing enemy Spies, as they may still be alive elsewhere. Thus, it's best to know some of the signs that tell that the Spy may not really be dead. Spies using the Dead Ringer cannot manually Cloak, and cannot use any weapons while invisible.

If an enemy dies to a single weak hit while approaching friendly lines without firing his weapon, it is most probably an enemy Spy disguised as one of his teammates. Most players don't run in with such low health, and a Spy disguised as a teammate will drop a corpse of the class he was disguised as.
- Similarly, if an enemy Spy disguised as a teammate approaches the front lines from the enemy's position, he is most likely using the Dead Ringer, even if he doesn't ‘die’ from the first hit. Remember that the Dead Ringer cannot Cloak at will, so a Dead Ringer Spy will rely on opponents' fire activating his feign death in order to become invisible.
- In general, if a player that has been identified to be an enemy Spy seems to be approaching a teammate suicidality, he is probably trying to get damaged so that his Dead Ringer will be activated, so try to track him down and kill him.

The decloaking sound of the Dead Ringer is very distinctive but requires players to be within a certain distance to hear it. Listen for it.

When a Spy is killed, check to see if their username is darker. If their username becomes normally colored after 3 seconds or less, that means they feigned their death.

Picking up the Spy's dropped ammo box does not replenish ammo or metal. This is an easy way to double-check if a recently-killed Spy is using the Dead Ringer or not.
- However, health packs dropped by a Spy which has activated the Dead Ringer (e.g. faking death in Medieval Mode) will still return health.

Being stopped while moving and not bumping into any visible objects can indicate that a Spy whose Dead Ringer was activated is trying to pass through.

If the Spy uses his Disguise Kit shortly before being "killed," the smoke effects will follow the Spy for the time that it takes for the Disguise to be equipped. Try to track any smoke that continues to move after an enemy Spy was killed.

If it is safe to do so, stand still or use a cancellable taunt after "killing" a Spy known to use the Dead Ringer. This may provoke the Spy into uncloaking nearby and making himself vulnerable. You can also check the scoreboard during this time, to see if the Spy "respawns" much faster than they should be able to.

Ragdoll physics not reacting proportionally to damage dealt.

Dealing with the Cloak and Dagger

The Spy's Cloak and Dagger allows him to stay cloaked indefinitely, and to hide in unconventional places while waiting for the right time to strike. An area that may seem impossible for a Spy to hide in may be sheltering a particularly cunning Spy who knows where the enemy team will not check for Spies.

In general, most Cloak and Dagger Spies will try to hide in corners in order to avoid being bumped into as they recharge their Cloak. Try to occasionally fire into corners or vantage points with wide fields of view.

One brute-force method for dealing with the Cloak and Dagger is to simply repeatedly check an area where the Spy is hiding. As the Cloak and Dagger has a relatively short charge meter, the Spy cannot make too many movements or their Cloak will run out and show their silhouette. If the Spy has L'Etranger equipped, however, chasing him down will be harder, as he will benefit from the extended cloak time, allowing him to dodge your attacks or simply sneak off elsewhere.

Some unconventional Spies will hide out in the open rather than against walls or in corners. This allows them to maneuver easily to avoid detection, and easily avoids the most often checked areas of a map. Try to keep this in mind if you suspect that a Spy is in the area.

Dealing with Your Eternal Reward

An enemy Spy using the Your Eternal Reward will instantly disguise as a teammate upon backstab without leaving a corpse. A Spy using Your Eternal Reward can be difficult to detect even when he is killing teammates nearby.

If one of your teammates gets backstabbed without appearing on your kill feed, identify their name and class, and by extension the Spy's disguise. Note that the Spy can manually change his disguise at the cost of the entire cloak meter.

If you get backstabbed by the Spy, clearly announce this to teammates, as well as the class that the Spy is now disguised as, to make sure that they know who he is disguised as. Again, beware that the Spy can manually change his disguise at the cost of the entire cloak meter.

When the Spy backstabs with Your Eternal Reward, the faint sound of the melee hit can be heard if close enough. This can serve as a key warning that a Spy might be killing your teammates in your immediate vicinity.

Remember that any backstabs made using Your Eternal Reward will not appear on the opposite team's kill feed. Pay very close attention to teammates' movements and listen for any melee hit sounds nearby.

When a Spy with the Eternal Reward backstabs a teammate, their body disappears, but their weapon remains sitting on the ground. If you see one of your teammates and their weapon on the ground, it's not a bad idea to Spy check them.