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Rating:

9/10

Razer’s Viper line has been one of the best options for competitive-level gaming mice since the V1 was introduced in 2019, packing top-of-the-line specs into an ambidextrous shape. The release of the Viper V4 allows Razer to remain competitive in the space, despite not breaking any tech barriers with major jumps in polling rates or DPI compared to the prior generation. With the V4, Razer focused on small, incremental improvements to squeeze more performance out of the same polling rate—a measure of responsiveness that gauges the frequency at which the mouse sends tracking data to your computer—by reducing latency and improving consistency.

While the Viper V4 Pro is a fantastic mouse, V3 owners should not rush to upgrade. The improvements to performance and weight are small across generations, but impressive numbers nonetheless. Because of this, the V4 is a compelling option if you’re more than a generation behind and looking for an upgrade.

If It Ain’t Broke …

Comparing the exteriors of the Viper V3 and V4, you’ll struggle to see any differences. The two are essentially identical, save for a minor change to the specific shade of white. While it’s easy to dismiss Razer’s iterative design as lacking in innovation, the shape of the V3 was already fantastic, requiring little, if any, improvements.

Like its predecessors, the V4 Pro is largely designed as an ambidextrous mouse. While some users might prefer a dedicated right-handed mouse for better ergonomics, the lightweight design will satisfy the needs of most gamers.

The top curvature is comfortable on your palm, and both the length and width are meant for average-sized hands. Both sides of the mouse taper slightly for easier lifting, and the side buttons are placed optimally on the left side for a standard palm grip. The lack of side buttons on the right means this isn’t a “true” ambidextrous mouse, but there aren’t many of those on the market anymore. Because of this, lefties will have to do without side buttons for the time being. The only significant difference from other mice is the two main buttons, which feature Razer’s signature concave shape.

To give the V4 lower latency and make the buttons last longer, Razer moved away from mechanical switches to optical sensors for the buttons and scroll wheel. Another benefit is that the tactile experience of each switch can be fine-tuned independent of the internal workings. With a standard mechanical switch, the two are inseparable from one another, which creates trade-offs between a switch's feel and its functionality.

The buttons have a short travel distance and an immediate, full-sounding click when pressed. The switches underneath require enough weight to prevent misclicks, but aren't so heavy as to make inputs feel slow. The new optical scroll wheel has a significant, separated bump between each input, snapping into place immediately while still being easy to rotate. The side buttons feel slightly softer, with a more muted tone compared to the two main buttons.

The real improvements to this generation's Viper are under the hood. Razer reduced the weight by 5 grams (totaling 50 grams in white, or 49 grams in black). The mouse’s guts are capable of 8,000-Hz polling (the same as the V3) and 50,000 DPI (15,000 more than the V3), and the new hemispherical dongle (which I loved when reviewing the latest Deathadder) looks better on a desk and provides more information at a glance.

While a 5-gram reduction in weight may sound minor, the improvements were immediately noticeable, leading to quick, snappy movements and flicks required in first-person shooters. In precision-focused games like Counter-Strike 2, the weight felt perfectly balanced to throw around without being so light that I lost control, and in fast-paced titles like Helldivers 2, the added agility gave me the ability to contend with multiple enemies at once (or, more accurately, easily turn around and flee from them).

Instead of the singular RGB indicator of the V3’s hyperpolling dongle, the desktop bio-dome has three programmable RGB indicators to display one of four different settings: connection quality, battery level, polling rate, and current DPI stage. The first two are indicated by a red-to-green gradient, and the last two will correspond with the predetermined colors for each stage. While all of these have their use, I found the indicators for connection quality and battery level to be the most practical.

Comfortable for Competition

The biggest improvement on the V4 is the introduction of Frame Sync. This system synchronizes the Viper’s optical sensor with your computer’s polling rate to eliminate the latency created by mismatches between the two. The V4 is rated for an average click latency of 0.204 millisecond and a motion latency of 0.36 millisecond. Such small margins are practically imperceptible to the average player (even the highest level of competitive players have reaction times above 100 milliseconds), but cutting down this number serves to reduce the already low potential for errors or mis-inputs. Even when testing the mouse for consistency in aim trainers, the level of error was imperceptible—human error will have a much larger impact on performance.

One of the most compelling aspects of Razer’s pro-level mice is the granular levels of customization offered through the Razer Synapse software (and the in-browser Synapse Web beta). Alongside typical adjustments for DPI and polling rates, the V4 also includes settings for sensor tracking distance, dynamic sensitivity with customizable curves, and mouse rotation.

These customizations allow the mouse to be tracked on frosted or transparent glass surfaces, for example. My favorite setting is the dynamic sensitivity adjustment, which allows for a more precise response from the mouse. While it will take some patience and time to fine-tune this setting, the benefits on tactical shooters like Counter-Strike and Valorant were immediate. This setting allows me to use rapid flick shots with precise aiming in those games.

Mouse rotation does exactly what it sounds like, allowing the sensor’s inputs to be rotated in relation to the mouse’s position.

For such a lightweight mouse, the battery life is impressive, lasting more than a week of consistent use with polling set to 8 kHz. Even charging between uses was impressively fast as well. The V4 is rated for up to 180 hours of battery life at 1,000 Hz (1 kHz), and up to 45 hours at 8 kHz. This nearly doubles the V3’s 95 hours at 1 kHz, and almost triples its 17 hours at 8 kHz. It’s an improvement over the Deathadder’s 150 hours at 1 kHz and 22 hours at 8 kHz, and is significantly more than Logitech’s quoted 90 hours at 1 kHz for the Pro X Superlight 2, and 95 hours at 1 kHz for the Pro X2 Superstrike.

While this mouse obviously isn’t designed for productivity-focused work, I found it more than capable for everyday use. It certainly isn’t as comfortable as an ergonomically-focused mouse like the Logitech MX Master 4 or the Hansker Productivity Mouse, but it’s more than enough for someone without any specialized ergonomic needs.

(Note: Something more ergonomic is always a good option for long-term health, and the best time to start is before you have any issues.)

Bendable Bodywork

Engineering a mouse to be this light is no small feat. A lot of sacrifices had to be made. From the outside, when everything is properly put together, this mouse is incredibly rigid, and everything feels sturdy without any creaks or quirks during use.

To achieve this, the V4's design isn't very repairable. While disassembling the mouse was relatively easy, as most components are secured with screws, braces, and plastic clips, many of the plastic components feel brittle and could be susceptible to breaking. Once assembled, these parts form a mouse that’s far more rigid than any of the components on their own, demonstrating how important clever engineering is when designing an ultralight mouse.

But because of this lightness, these components aren’t ideal for repairs: Replacing a switch, scroll wheel, or battery can risk breaking the internal supports or the plastic clips. This is inherent to any ultralight mouse, but still worth mentioning for DIY-ers and longevity considerations. Repairs are possible but require patience and care.

My biggest complaint with this mouse is that four generations later, the Viper Pro still lacks Bluetooth connectivity. Because these are esports-focused mice, Razer's goal was to eliminate unnecessary weight like RGB lighting, repairability, and Bluetooth connectivity. While adding a Bluetooth chip would add weight, the exclusion limits the usability of this mouse outside of a desktop PC.

Beyond nitpicks over repairability and connectivity, the Viper V4 Pro is an impressive mouse. It’s comfortable, lightweight, and improves on the very few downsides of the previous generation. There’s not much reason to upgrade from the V3, but if you’re cross-shopping between the V3 and V4, there’s hardly any reason to opt for the older unit (unless you can find it at a significant discount)—the V4 is an improvement across every metric.

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