The Thief Meter is a representation of the health of the current player character and, when applicable, boss or ally. Below the health is a yellow Gadget Meter (also called "Focus" or the "Gadget Gauge") which is depleted by using power-ups. The Gadget Meter will not appear on the Thief Meter until a power-up that uses it is purchased for the character (except in Sly 3: Honor Among Thieves where all characters, regardless of power-ups, start with a Gadget Meter).
The remaining-health section usually matches the main color of the character's face symbol. As damage increases, the healthy section decreases in size from right to left. Depending on the character, the damaged part of the health meter is colored either red or a darker shade of the health color.
Entering the safe house fully replenishes the Thief Meter, but it can also be partly replenished by collecting health, which can be obtained by smashing objects or defeating enemies, similar to coins.
Sly Cooper and the Thievius Raccoonus
In Sly Cooper and the Thievius Raccoonus, the Thief Meter is only used by bosses, and also in the form of a health bar, as opposed to the modern version. When the boss is attacked, the meter will shrink from up to down. At the bottom of the health meter, there is a cinematic image of the boss's head, which changes over time as Sly attacks the boss to indicate how much they have been beaten up. The image often depicts the boss as screaming when they are at full health, though Mz. Ruby and Clockwerk are exceptions. When the boss has been defeated, the image will make its final change, though this will usually only appear for a split second.
Sly 2: Band of Thieves and Sly 3: Honor Among Thieves
In Sly 2: Band of Thieves, the Thief Meter finally maintains its modern design and use, and is now used by the Cooper Gang.
When the player has not been seen by any enemies, the Thief Meter remains static and only changes when health is lost (where it pulsates red once) or health is acquired.
When the player is in close proximity to an enemy or performing a sneaky action (such as interacting with stealth auras next to a ledge), the Thief Meter will emit yellow rings, and the background music will typically transition to a staccato tune.
When the player has been discovered by an enemy or is under attack, the face symbol in the Thief Meter will begin to continuously pulsate red (and the music will become more fast-paced), and will continue to do so until the player has escaped or all pursuing enemies have been defeated. Once that occurs, the Thief Meter and the background music will return to normal.
Bosses have a similar health meter to the player, albeit without a Gadget Meter. The pirate ship in Sly 3 has two health bars, which are similar to those of the bosses in Sly Cooper and the Thievius Raccoonus. each representing a side of the ship. If either is depleted, the ship sinks.
Whenever a power-up is used, the Gadget Meter loses a set amount of focus that changes depending on the power-up. In the case where a power-up is activated and deactivated, the Gadget Meter will be depleted at a steady rate, one example being Shadow Power.
Similar to the Thief Meter, health packs replenish a portion of the Gadget Meter, and going back to the Safe House fully replenishes it.
Carmelita Fox, the Guru, the Panda King and Dimitri Lousteau are playable characters in Sly 3 that have Gadget Meters, but never use it as they don't have power-ups. An exception to this is that Carmelita can use power-ups in multiplayer.
In the third game, the Gadget Meter also represents how much ammo the biplane has left.
Sly Cooper: Thieves in Time
Thief Meters have been modified from their original functionality and appearances in Sly 2 and Sly 3. They are now slightly transparent so they do not completely block the background. The character face symbol's eyes consistently flash white, and other accessories have special animations as well (like the Thief Costume's earrings shining and the end of El Jefe's cigar glowing and smoking).
When the player is in close proximity to an enemy, the Thief Meter no longer shows any indication of it (the music no longer changes, as well). However, it still emits rings (red instead of yellow) when the player is doing something sneaky.
Instead of the face symbol consistently pulsating red when the player has been discovered by an enemy or is under attack, the Thief Meter now shows flashing red and blue lights on either side of the meter, emulating a police siren. The music still changes. Taking any amount of damage, whether inside or outside of battle, will cause the character face symbol to pulsate red once and then return to normal.
The Gadget Meter is used a bit more aggressively. Just like in Sly 2: Band of Thieves, the Cooper Gang's gadget meters do not appear before power-ups are purchased. Unlike its usages in Sly 2 and Sly 3, the meter slowly and automatically replenishes itself, but all power-ups now use much more focus than their counterparts in the previous games, one example being the Smoke Bomb, which uses up all focus with only one use. When the meter finishes replenishing itself, a little beep can be heard.
- For most gadgets in Sly 2, if you completely use up all your power, the meter won't be completely empty, usually showing just a small bit of power left. It could be because in this game, there has to be a certain amount of focus left to still be able to use the gadget.
- In several demos for Sly 2, the Thief Meter's appearance is different from the released game. This version of the Thief Meter is inconsistently used in the released version of Sly 2 for certain missions to represent the health of objects such as Bentley and a helicopter.
- In the PlayStation 3 versions of Sly 2 and 3, the health section of the Thief Meter does not become completely filled when health is at maximum due to a glitch, leaving behind a small portion of the meter unfilled permanently. This may be a result of the Thief Meter's outline being thinner than in the PlayStation 2 versions of the games. This may be a bug in the original PS2 versions as well, as the right end of the meter appears to be slightly darker than the left end.
- In Thieves in Time, Salim al-Kupar, Rioichi Cooper and Carmelita are the only playable characters to not have a Gadget Meter.
- There is a glitch that occasionally occurs in Thieves in Time; when leaving combat, the Thief Meter's "siren" effect will not stop. This seems to happen at random.