Think of a CPU cooler as a car's radiator system. The base plate grabs heat from the engine (the CPU), heatpipes or liquid carry it away, and fins or a radiator hand it to the air. Fans are the wind blowing through. Size specs tell you if it fits under the hood, socket specs tell you if it bolts on, and fan specs tell you how much noise it makes doing the job. Check fit first: a great cooler that does not fit is worthless.
The cooling design: air tower, low-profile air, or AIO (all-in-one) liquid cooler with a pump and radiator.
When it matters: Good towers match mid-size AIOs for most CPUs and have no pump to fail. Large AIOs lead on the hottest chips. Liquid is not automatically quieter, since the pump always runs.
The shape of an air cooler: single tower, dual tower, or top-down (fan blowing down onto the board).
When it matters: Dual towers cool more but are wide and can block RAM slots. Top-down coolers suit small cases and also cool the board's power parts.
Skip it if: You are buying a liquid cooler.
How tall the air cooler stands above the CPU, in mm, including the fan.
When it matters: Trap: the most common fit failure. Compare it with your case's CPU cooler clearance and leave a few millimeters of margin, or the side panel will not close.
Skip it if: You are buying a liquid cooler.
How wide the cooler is, in mm, across the fins and fans.
When it matters: Wide coolers can overhang RAM slots, the top graphics slot or M.2 heatsinks. Check your board's layout in small cases.
Skip it if: You use a full ATX board in a roomy case.
How much the cooler weighs, in grams.
When it matters: Very heavy coolers strain the board during shipping. Remove them before moving a PC long distances.
Skip it if: Your PC will not travel.
The tallest RAM stick that fits under the cooler's fins, in mm.
When it matters: Trap: tall RGB memory often collides with big towers. Compare with your RAM's module height, or move the front fan up if the design allows.
Skip it if: You use low-profile RAM or a liquid cooler.
Whether the cooler covers the RAM slot nearest the CPU.
When it matters: Matters if you need all four slots or tall RAM. On many boards two sticks go in the second and fourth slots, so a blocked first slot may not matter.
Skip it if: You run two sticks in the slots away from the CPU.
The radiator's length class, named after its fans: 120, 240, 280, 360 or 420 mm.
When it matters: Bigger radiators cool more and let fans spin slower. Trap: check your case supports that size at the mount you want. 120 mm units rarely beat a good air tower.
How thick the radiator is, in mm, and the total thickness with fans attached (stack height).
When it matters: Thicker radiators cool better but need more room. Trap: a top-mounted thick radiator can hit tall RAM or board heatsinks.
Skip it if: Your case has generous radiator clearance.
How far the pump block sticks up from the CPU, in mm.
When it matters: Matters in slim cases and when mounting a graphics card vertically near the CPU.
Skip it if: You use a standard mid-tower case.
The length of the liquid tubes between pump and radiator, in mm.
When it matters: Short tubes can stop a front-mounted radiator reaching in big cases. Keep the pump below the radiator's highest point to avoid air noise.
Skip it if: You mount the radiator on the top of a mid-tower.
The pump's top speed, in RPM.
When it matters: Higher RPM does not mean better cooling. Pumps can whine at full speed, so a board or app that slows the pump helps quiet builds.
Skip it if: You leave the pump on the maker's default profile.
A small fan on the pump block that blows over the board's power delivery parts.
When it matters: Liquid coolers leave no airflow around the CPU socket. This fan helps boards with weak VRM heatsinks during heavy loads.
Skip it if: Your board has large VRM heatsinks and your case has good airflow.
The heat load the maker says the cooler can handle, in watts.
When it matters: Reality check: makers test differently, so ratings do not compare across brands. Use it as a rough floor above your CPU's real turbo power, not its base TDP.
How many sealed heat-carrying tubes connect the base to the fins.
When it matters: More heatpipes carry more heat, but pipe thickness and fin design matter just as much. Compare within one brand's lineup, not across brands.
Skip it if: You compare coolers by tested results.
What the part touching the CPU is made of, usually copper, nickel-plated copper, or aluminum.
When it matters: Copper conducts heat better. Trap: liquid metal paste attacks aluminum, so never pair it with an aluminum base.
Skip it if: You use normal paste.
Which Intel and AMD CPU sockets the included mounting hardware fits.
When it matters: Trap: LGA1700 and LGA1851 need different brackets from older Intel coolers. AM5 takes most AM4 coolers that use the stock backplate. Older coolers may need a free bracket from the maker.
Whether the maker confirms the cooler will fit LGA1954, Intel's next desktop socket expected for Nova Lake chips.
When it matters: Useful if you plan to move to that platform and keep the cooler. A free bracket may be offered later.
Skip it if: You are staying on AMD or your current Intel platform.
A mounting option that shifts the cooler slightly toward the hottest area of AMD Ryzen 7000 and 9000 chips.
When it matters: The hottest area on these chips is not at the center, so an offset mount can help temperatures slightly.
Skip it if: You use an Intel CPU.
Whether the cooler ships with a frame that replaces the stock Intel CPU retention bracket.
When it matters: On LGA1700 and LGA1851 the stock bracket can bend the CPU slightly. A contact frame gives more even pressure and better contact.
Skip it if: You use an AMD CPU.
How the cooler attaches: backplate type, screws or clips, and whether the board must come out.
When it matters: Mounting is one of the harder build steps. Front-access screws and a pre-fitted backplate save time. Do not overtighten.
The size (usually 120 or 140 mm) and number of fans included.
When it matters: Larger fans move the same air at lower speed, so they run quieter. Adding a second tower fan helps a little on heavy loads.
The fans' top speed, in RPM.
When it matters: Higher top speed means more cooling headroom and more noise. Most of the time fans should run well below it.
Skip it if: Your fans follow a sensible fan curve.
How much air the fan moves, in CFM (cubic feet per minute), and how hard it pushes through resistance, in mmH2O.
When it matters: Radiators and dense fins need high static pressure. Reality check: both are measured at maximum speed without obstruction, so real performance is lower.
The part the fan spins on: sleeve, rifle, fluid dynamic, ball or magnetic.
When it matters: Sleeve bearings are cheapest and wear out soonest, especially lying flat. Fluid dynamic and magnetic bearings last and stay quiet.
Skip it if: The cooler comes from a reputable brand with a long warranty.
How fan speed is controlled: 4-pin PWM (pulse width modulation) gives smooth control, and zero RPM mode stops fans at low load.
When it matters: PWM fans quiet down smoothly at idle. Trap: some coolers need their own hub, USB header or app instead of a standard fan header.
The maker's claimed maximum loudness, in dBA.
When it matters: Reality check: makers measure differently, and numbers are not comparable across brands. The sound's tone matters too. A pump whine can annoy more than louder fan hiss.
Whether the cooler has RGB lighting or a screen on the pump block, and the screen's size.
When it matters: Screens add cost and usually need the maker's software running. Trap: some displays need a USB header, which boards have few of.
Skip it if: You care only about cooling and noise.
Whether the cooler's fans, lighting or screen need the maker's own hub or software.
When it matters: Locks you into that brand's software for control. Several lighting apps running together can conflict.
Skip it if: You use plain fans on standard headers.