MOBIUZ EX321UZ — 31.5-inch 4K QD-OLED Gaming Monitor

This article covers the ベンキュージャパン BenQ ゲーミングモニターMOBIUZ EX321UZ 31.5インチ, known internationally as the BenQ MOBIUZ EX321UZ: a 31.5-inch 4K QD-OLED gaming monitor running at 240Hz.

Instead of repeating the spec sheet, this guide focuses on whether your PC can actually feed 4K at 240Hz, how seriously to take burn-in, and who should not buy it.

Overview

The MOBIUZ EX321UZ pairs a 31.5-inch 3840x2160 QD-OLED panel with a 240Hz refresh rate and a 0.03ms GtG response time, putting it at the very top of the consumer gaming monitor market.

Peak brightness reaches 1000 cd/m2 in HDR, the panel carries VESA DisplayHDR True Black 500 certification, and it covers 99% of DCI-P3. The short version: this is a monitor for people who refuse to choose between 4K image quality and high refresh rates.

If frame rate alone is the goal, the same money buys a more rational setup.

BenQ includes its AI-powered Smart Game Art feature, which draws on more than 120 learned scenarios to pick a color mode automatically. Gradient color correction and High Pixel contrast adjustment refine the image further, and a bundled remote control makes the on-screen menu usable from the desk.

KVM functionality and a built-in USB hub make it a practical hub for a multi-device setup.

At 31.5 inches, 4K works out to roughly 140 ppi, so 125-150% scaling is the practical setting on Windows.

If you plan to run it unscaled, expect small text.

Compatibility Guide

Connectivity is comprehensive: two HDMI 2.1 ports, one DisplayPort 2.1, and one USB-C that carries video, data, and up to 65W of power delivery.

All video inputs accept 4K at 240Hz. BenQ notes that Smart Game Art is PC-only and requires the Color Shuttle software on Windows.

Three practical caveats. First, 4K at 240Hz is a heavy signal, and it is generally carried with DSC (Display Stream Compression).

That means a reasonably recent GPU with DSC support and a properly certified cable. If the picture flickers or 240Hz disappears after swapping the bundled cable for a generic one, suspect the cable first.

Second, current game consoles generally top out at 4K/120Hz. The monitor accepting 240Hz and your console producing it are two different things, and this is where most disappointment comes from.

Buying this panel for a console means paying for headroom you will only use later on a PC.

Third, 65W of USB-C power delivery is enough for a thin-and-light laptop over a single cable, but gaming laptops and mobile workstations often ship with adapters above 100W. On those, the battery can drain under load even while connected.

Check the wattage on your laptop's own adapter before counting on single-cable operation.

The KVM feature shares one keyboard and mouse between two PCs and follows the input source, but it needs a USB upstream link from each PC (USB-C or the bundled USB cable). A video cable alone will not do it.

An eARC-capable HDMI port also allows clean audio output to a soundbar.

For mounting, make sure the desk has the depth for a 31.5-inch panel and its stand.

If you plan to use a monitor arm or wall mount, confirm VESA support, hole spacing, and panel weight on the manufacturer's product page, since those figures are not in the spec list used for this article.

Product Info

The EX321UZ launched in 2025 and sits firmly in the premium tier. The headline numbers are a 31.5-inch 4K QD-OLED panel, 240Hz, 0.03ms GtG, DisplayHDR True Black 500, 1000 cd/m2 peak HDR brightness, 99% DCI-P3, two HDMI 2.1 inputs, DisplayPort 2.1, USB-C, KVM, eARC, and a USB hub.

Of those, the two HDR figures matter most in daily use. The 1000 cd/m2 peak applies to small highlight areas; a full white screen sustains considerably less, as with OLED panels generally.

True Black 500, by contrast, measures how deep the blacks go, which is exactly where this panel earns its price. It is a monitor built for dim rooms.

Check the retailer's page for the latest price.co.jp as captured on 26 August 2026.

OLED monitors swing hard on sales, so treat any figure here as a snapshot and check the listing for the current price before buying. Overseas marketplace listings vary too much per seller to serve as a reference point.

Check the retailer's page for the latest user reviews. That is a healthy sample for a monitor above 200,000 yen.

Keep in mind, though, that expensive hardware tends to be reviewed shortly after purchase, so the things that actually decide an OLED's fate over two or three years, brightness falloff and burn-in, are barely represented in that number. Read the star rating as an indicator of out-of-box quality.

The monitor carries a three-year manufacturer warranty. Included accessories: power cable, DisplayPort cable, HDMI cable, USB-C cable, remote control, quick start guide, and a factory calibration report.

Whether burn-in is covered depends on specific conditions, so review the warranty terms before purchase.

Living With Burn-In Risk

Buying QD-OLED means accepting responsibility for burn-in management. The rule is simple: do not leave the same image in the same place for hours.

Four habits cover most of it. Auto-hide the Windows taskbar, use dark themes to shrink bright areas, set the screen saver and display sleep timers short (around ten minutes), and let the monitor sit in standby rather than cutting power at the wall, since panel maintenance routines usually run while idle.

Some things you can stop worrying about. Games and video move constantly, so they pose little risk.

The danger is static UI: streaming overlays, spreadsheet header rows, always-on hardware monitoring widgets. If that is your main workload for eight hours a day, an IPS panel will serve you better than this one.

Alternatives and Competitors

The obvious rival class is a 4K IPS monitor around 160Hz. It cannot match this panel's blacks or contrast, but it holds sustained brightness better and carries no burn-in anxiety, which suits bright rooms and office-heavy use.

A 1440p high-refresh LCD is the other direction: for competitive shooters, the total cost including the GPU needed to drive it is far lower.

At the extreme ends, BenQ's own ZOWIE XL2540X+ represents the esports-first philosophy with a Full HD 280Hz TN panel, trading image quality for responsiveness and price. If you want OLED but bigger, LG's 39GX90SB-W at 39 inches or the 48.8-inch 49GR85DC-B ultrawide are the usual alternatives.

The choice is screen size versus 4K pixel density.

What makes the MOBIUZ EX321UZ distinct is that it bundles 4K, 240Hz, QD-OLED, DisplayPort 2.1, KVM, a remote, and eARC into one chassis.

Pick any single metric and something beats it, but few monitors answer all of those requirements at once.

Who It Is For

First, gamers who want maximum image quality and response for shooters and racing games. QD-OLED contrast plus 240Hz is genuinely competitive-grade.

The prerequisite is a GPU that can push high frame rates at 4K, upscaling and frame generation included, so check what your card realistically delivers before ordering.

Second, creators who also game. 99% DCI-P3 coverage and the included factory calibration report support color-critical photo and video work.

Just plan around burn-in if your editing timeline sits on screen unchanged for hours.

Third, anyone juggling several PCs or consoles. The KVM and USB hub consolidate the desk, and the remote means never reaching behind the panel to switch inputs.

For someone moving between a work laptop and a gaming desktop, that convenience alone justifies part of the premium.

Before You Buy

First, a listing accuracy warning. The Amazon product data for this monitor has been observed showing a manufacturer name other than BenQ.

Listing metadata depends on seller registration, so mismatches like this are not unusual. Confirm from the product images and title that you are buying the BenQ MOBIUZ EX321UZ itself, and check the seller and fulfiller too.

Ordering on the strength of a model number or ASIN alone risks receiving a different product.

Second, buying 240Hz does not mean playing at 240Hz. Holding high frame rates at 4K is demanding even for current flagship GPUs.

Most people who feel underwhelmed after buying an expensive monitor are limited by the graphics card, not the panel, so budget for both together.

Third, the room. Ambient light raises OLED black levels and erodes the contrast advantage that justifies the price.

Facing a window, or working in a shared space where the lights stay on, wastes the panel's strongest feature.

Fourth, Smart Game Art is PC-only and needs the Color Shuttle software installed. If this is destined for a console-only setup, assume that feature is unavailable.

KVM likewise requires the USB upstream connection, not just a video cable.

Finally, if 120Hz is enough for you, or the budget has a ceiling, this monitor is overkill. Move the money to a 4K 144Hz LCD or a high-refresh 1440p panel and spend the difference on the GPU.

The honest list of reasons to skip it: a bright room, long hours of static UI, console-only use, and being satisfied with 120Hz.

FAQ

Q. What do I need to actually run 4K at 240Hz? A.

A certified DisplayPort 2.1 or HDMI 2.1 cable and a reasonably recent GPU with DSC support.

Whether games reach 240fps is a separate question that depends on title and settings, usually with upscaling or frame generation in the mix.

Q. Will a console run at 240Hz? A.

The monitor accepts the input, but current consoles generally output 4K at up to 120Hz. Check the console's own specification.

Q. How worried should I be about burn-in? A.

Moving content carries little risk, but do the basics: auto-hide the taskbar, use dark themes, and keep sleep timers short. The warranty runs three years, though burn-in coverage depends on conditions, so read the terms first.

Q. Can I connect a laptop with a single USB-C cable? A.

Yes for video, data, and charging, but power delivery tops out at 65W. Gaming laptops with adapters above 100W may still lose battery under load.

Q. What does KVM need to work? A.

A USB upstream connection from each PC (USB-C or the bundled USB cable) in addition to the video cable. Without it, keyboard and mouse sharing will not function.

Q. When was the price captured? A.

The 228,041 yen figure is from 26 August 2026. OLED pricing moves quickly, so verify the current price on the listing.