IPS Glow Test: Free Online Backlight Bleed Test
IPS Glow Test. Dim the room and click Start IPS Glow Test to run this IPS glow test and tell normal glow apart from backlight bleed. The monitor ghosting test works on any screen — laptop, external monitor, or TV — with nothing to install.
Interactive Tool
Run the IPS Glow Test to tell normal IPS glow apart from backlight bleed, a distinction that matters if you're deciding whether a panel is defective enough to return. Click Start IPS Glow Test, dim the room, and move your head side to side while watching the corners of the black field — glow shifts and fades as your viewing angle changes, while true backlight bleed stays fixed in place no matter how you move.
Seeing a pale haze in the corners of your new monitor during a dark scene? This IPS glow test fills your screen with a fullscreen black field so you can check the corners and edges and tell IPS glow, which shifts with your viewing angle, from backlight bleed, which stays put. It works on any monitor, laptop or TV with an LCD backlight, and it helps you decide whether those bright spots are normal screen uniformity behaviour or a bleeding backlight worth sending back.
How to Run the IPS Glow Test Step by Step
The IPS glow test only needs a browser and two minutes. Follow the steps in order so you test IPS glow under the same conditions you actually use the display in: The monitor flicker test tool runs fullscreen so you can inspect your panel edge-to-edge under real viewing conditions.
- Wipe the display with a dry microfiber cloth so dust and smudges don't pass for uneven light.
- Open the black screen, enter fullscreen and hide the cursor.
- Give your eyes 30 seconds or more to settle before you judge anything.
- Check each corner, each edge and the centre, then move your head and look again.
Prepare a Dark Room, Not a Pitch-Black One
A dark room exposes faint light, but total darkness and maximum brightness exaggerate every flaw. Dim the room lighting until reflections disappear, keep a little ambient light behind you, and set the screen to the brightness you normally use. Leave HDR and picture modes as they are for your daily work, so the result reflects your real setup rather than a showroom stress setting.
Scan the Corners on Pure Black From Your Normal Seat
Sit at your usual viewing distance with your eyes level with the middle of the screen. On pure black, look for glowing corners, a soft silver cloud, or a sharp bright patch along an edge. Look at the display head-on first, then lean left, right, up and down. Note where each mark sits and whether it changes, because that one observation drives the rest of the diagnosis.
IPS Glow vs Backlight Bleed: Watch What Moves
Both artifacts show up on dark content, but they behave differently when your eyes move. The glow shifts with angle: the haze grows, fades or slides as you change position. Backlight bleed holds a fixed position because the light escapes at a physical point in the display. If you only remember one rule of ips glow vs bleed, it is this: moving haze is glow, a locked patch is bleed.
| Check | IPS glow | Backlight bleed |
|---|---|---|
| Moves when you move | Yes, size and brightness change | No, stays in one spot |
| Typical look | Silvery, yellowish or bluish haze | Bright patch or beam of light from an edge |
| Where it appears | Corners, strongest nearest your eye line | Edges and corners, sometimes blotchy |
| Panels affected | IPS panels only | Any LCD |
Why an IPS Panel Glows Off-Axis
An IPS panel rotates its liquid crystal layer sideways, which gives IPS panels their wide viewing angles and strong color consistency. The catch is that some backlight escapes when you look at a black area from a steep angle, and the corners of a big screen are always seen at a steeper angle than the centre. You can work out how steep with one formula:
$$\theta_{corner} = \arctan\left(\frac{\text{diagonal} \div 2}{\text{viewing distance}}\right)$$
Take a 34-inch ultrawide gaming monitor viewed from 70 cm. Half its diagonal is 43.2 cm, so each corner sits at \(\arctan(43.2 \div 70) = 31.7^\circ\). Push the chair back to 90 cm and the angle falls to 25.6°, a 6.1° cut that visibly softens the glow. A 23.8-inch screen at 70 cm sits at only 23.4°, which is why a large screen glows more at the same desk. A small tilt so the screen faces your eyes also helps.
What Causes Backlight Bleed in an LCD Panel
Every LCD panel needs a backlight of LEDs behind the liquid crystals, spread evenly by a light guide plate and a diffuser. Backlight leaks happen when that stack doesn't seal at the edges. The usual causes are:
- Frame pressure from a bezel or chassis that presses unevenly on the glass
- Gaps from panel assembly or assembly tolerance on the production line
- Uneven pressure from a stand, bracket or shipping knock
- Panel aging and lower build quality that let layers warp
The sharpest form is flashlighting, a cone of light that fans out from one corner. Some backlight bleed exists on all LCD screens; the question is only how much.
Black, Near-Black and Dark Gray Fields in a Backlight Bleed Test
A good backlight bleed test shows more than one dark field, because each level hides or reveals different faults. The table below converts the digital level of each field to its approximate light output using a 2.2 gamma curve, so you can see how little light a field just above black really asks for. Run the monitor clouding test to check your display for this issue directly in your browser — no download required.
| Field | RGB level | Approx. light output | What it reveals |
|---|---|---|---|
| Pure black | 0 / 255 | 0% | Edge leaks, flashlighting and IPS glow |
| Near-black | 8 / 255 | 0.05% | Faint non-uniformity just above black |
| Dark gray | 32 / 255 | 1.0% | Clouding and blotchy brightness uniformity |
| Mid-gray | 128 / 255 | 22% | Tint shifts and dirty-screen patches |
White is useful only as a rule-out field for dust, reflections, a dead pixel or stuck pixels. It won't show bleed, because every part of the screen is already lit.
Clouding, Mura and Blooming vs Screen Bleed
Not every uneven patch is screen bleed. Clouding, also called mura, is a blotchy, cloud-like unevenness that usually sits in the middle of the screen rather than at the edges, and it shows best on the 32/255 field. Blooming is a halo around bright objects on local-dimming screens and follows the object as it moves. A mark shaped like a taskbar or game HUD is burn-in or image retention, not leakage. Name the shape first, then check it in normal dark content before deciding what it is.
Running a Backlight Bleed Check on a New 31.5-Inch Monitor
A colourist I'm helping has a 31.5-inch QHD IPS monitor on day three of a 14-day return window, and the decision is simple: keep it or swap it. The answer, after twenty minutes: keep it, because the corner haze is normal glow and the one fixed patch is too faint to matter in real footage.
The desk is shallow, so her eyes sit 63.5 cm from the screen. She sets brightness to her editing level of 35 in the on-screen menu, dims the room to one lamp behind her, opens the black field fullscreen and waits a full two minutes. Two things show up: a warm haze in the lower-left corner, and a thin strip about 3 cm long on the bottom edge, right of centre.
Next she leans 20 cm to the right. The lower-left haze swells and the lower-right corner starts glowing too, so that part is IPS glow. The bottom strip doesn't move at all: that is backlight bleed, a fixed leak.
The geometry explains why the haze is so strong. Half of a 31.5-inch diagonal is 40.0 cm, so at 63.5 cm the corners sit at \(\arctan(40.0 \div 63.5) = 32.2^\circ\). I reran the formula at other distances to see what moving the desk would buy:
| Eye distance | Corner angle |
|---|---|
| 63.5 cm (her desk now) | 32.2° |
| 74.1 cm | 28.4° |
| 78 cm (desk pulled forward) | 27.2° |
The 74.1 cm row is the break-even I solved for: there her corners match the 28.4° a 27-inch screen shows at 63.5 cm, so a smaller monitor buys nothing that 10.6 cm of distance doesn't. She pulls the desk forward to 78 cm and reruns the black field. The lower-left glow fades to a faint tint while the bottom strip stays exactly where it was, which confirms the split between glow and bleed.
The check that settles the bleed is real content. She scrubs through a night exterior in her grading software at the same brightness, and the bottom strip isn't visible in the image area. It only appears on the pure black field.
The caveat I'd flag: her grading app shows black letterbox bars on 2.39:1 footage, and the strip sits right where the lower bar is. If she delivers mostly scope-ratio work, that patch will be in view every day, and the return becomes worth it. The input that matters most here isn't brightness; it's what kind of content will sit over that edge.
Backlight Bleed by Panel Type: IPS, VA, TN and OLED
Your display technology decides which artifact you are likely to see, so check the spec sheet before you run the test.
| Type | IPS glow | Bleed risk | Trade-off |
|---|---|---|---|
| IPS | Always present to some degree | Moderate, mostly corners | Accurate colour, weaker contrast |
| VA panel | Minimal | Blotchy dark areas on large sizes | Deeper black level, slower dark transitions |
| TN panel | None | Least likely | Strong color shift off-axis |
| OLED | None | None, no backlight | Self-emitting pixels give perfect blacks |
If dark-room viewing matters most to you, an OLED screen removes both problems at the source.
How to Reduce Corner Glow and Backlight Bleeding
You can't remove corner glow or backlight bleeding entirely, but a few setup changes make both far less visible.
Lower Brightness and Add Bias Lighting
Dropping brightness lowers the whole black floor, so glow and leaks shrink with it, and it eases eye strain in dark scenes. If dark games then look too murky, raise the in-game shadow detail or gamma setting instead of brightness. Bias lighting, such as LED light strips set to a 6500K white behind the monitor, raises perceived contrast and black levels so the corners stop drawing your eye.
Fix the Viewing Angle and Check Mounting Pressure
Sit straight on: adjust seat height so your eyes meet the screen centre, and use a monitor arm to tilt the screen precisely. For bleed, loosen any over-tightened VESA screws and check that the mounting bracket isn't twisting the chassis. A short break-in period can help as thermal cycling relaxes the frame, but don't count on it. Rerun the black field after each change: if a fixed patch shrinks once the screws are re-seated, it was pressure bleed, while a tint that only follows your head is glow.
Judging Backlight Bleed in Normal Use Before a Return
Judge the display in normal use, not only on a black test field. Play movies with black letterbox bars or a dark gaming scene. If fixed light leakage breaks immersion or harms picture quality there, treat it as a manufacturing defect; if it only appears on a black field in a dark room, it is normal LCD behaviour. Swapping for IPS glow is a gamble, since panel variance means the next unit may be no better.
Warranty, Exchange and Replacement Options
Before you file anything, note which test field shows the leak, where it sits and that it stays put when you move, since a claim for glow alone is rarely accepted. Then check the retailer's return window, because an exchange is usually faster than a warranty claim. Manufacturer policies differ: some list a pixel and leakage tolerance and a specific inspection setup, so follow that procedure exactly. A replacement is easiest to win when the leak is large, near the centre, or visible in everyday content.
Why a Phone Camera Exaggerates Light Bleed
A phone camera on auto exposure brightens a black screen far beyond what your eyes see, and night mode or long exposure makes faint light bleed look severe. For a fair photo, use manual exposure, shoot straight on from your seat, and record your brightness and room light alongside it.
What a Fullscreen Bleed Test Can't Tell You
A browser-based backlight bleed check shows controlled fields; it doesn't measure luminance, and calibration software can't fix physical light leakage. Treat the result as evidence for your own judgement, not a verdict on the hardware.
OLED, Mini LED and Local Dimming Screens
OLED has no backlight, so a dark-screen mark there is uneven output just above black or retention, not bleed. A Mini LED screen with local dimming may switch zones off on an all-black field and hide backlight bleed completely, so test it on a very dark field and with a small white window on screen, where real content keeps the zones lit.
Frequently Asked Questions
- Is IPS glow a defect?
- Usually not. Every IPS panel lets some light through at steep angles, so a corner haze on a black screen is normal. It only becomes a problem if it intrudes on the films, games or work you actually use the monitor for.
- How do I tell IPS glow from backlight bleed?
- Move your head while the black field is on screen. IPS glow changes in size, brightness or colour as your angle changes. Backlight bleed stays locked to the same spot on the screen.
- Can IPS glow be removed?
- No, it comes from how IPS panels are built. You can make it much less visible by lowering brightness, sitting centred and a little further back, and adding bias lighting behind the monitor.
- Should I run the test at maximum brightness?
- Start at the brightness you normally use. Maximum brightness in a pitch-black room exaggerates both glow and bleed, so treat it only as an extra stress pass.
- Why does my phone photo make the glow look worse?
- Phone cameras raise exposure on dark scenes, so faint glow looks severe in the picture. Judge with your own eyes, or use manual exposure and shoot straight on from your seat.
- Do OLED monitors have IPS glow?
- No. OLED pixels make their own light and switch fully off, so there is no backlight to glow or bleed. A mark on an OLED black screen is a different issue, such as uneven near-black output or image retention.
- When is a glowing screen worth returning?
- When a fixed bright patch is visible in normal content at your usual brightness and room lighting. Glow that only appears on a black test field in the dark is normal, and a replacement unit may show the same amount.