ByteScope

Display & Monitor Test

Check your screen for defects and read out what your display really supports.

Your files never leave your browser — all processing is local.

Display info

Measured refresh rate
measuring…
Resolution (CSS px)
0 × 0
Physical estimate
0 × 0
Device pixel ratio
1.00
Viewport (live)
0 × 0
Color depth
0-bit
Pointer precision
coarse
Max touch points
0
Color gamut
unknown
HDR (display / video)
no / no

Gamut could not be detected by this browser.

Test patterns

  • Dead / stuck pixel

    A pixel that never changes on any color is dead; one stuck on a single hue is stuck — a healthy panel shows one flat, uniform color on every step.

    Click / space to cycle black → white → red → green → blue.

  • Uniformity / backlight bleed

    Turn brightness up and look for glow at the edges/corners on black, or dim patches on white — a healthy panel is flat and even edge-to-edge.

    Click / space to switch between pure black and pure white.

  • Banding / gradients

    A healthy 8-bit+ panel shows a smooth ramp; visible discrete steps or color casts in the ramp indicate banding or a poor color LUT.

    Click / space to cycle gray, red, green, blue 0–255 ramps.

  • Gamma chart

    Find the swatch where the striped half and solid half look equally bright when squinting — that column's number is your effective gamma (2.2 is the common target).

    No controls — read the chart at your normal viewing distance, then squint.

  • Ghosting / motion clarity

    A healthy fast panel keeps the moving blocks crisp; ghosting/blur trailing behind them at higher speeds indicates slow pixel response.

    Speed slider (1–16 px/frame), frame-locked motion.

  • Text sharpness

    Text should look crisp and evenly weighted at your normal scaling; blur, color fringing, or uneven stroke weight suggests a scaling or subpixel-rendering issue.

    Static — compare sizes 10–24px, sans & mono, both polarities.

  • Touch test

    Every touch/click should track smoothly with no dropped points, jitter, or dead zones across the whole surface — works with mouse too.

    Touch, pen or mouse — each contact gets its own color, ID and trail.

  • HDR capability & headroom

    Read the matrix: a ✓ under Decode means this browser can decode that HDR codec on this machine; whether you actually see HDR also needs the display to report HDR (top rows). The ramp checks highlight separation, not absolute nits.

    Feature-detected matrix (display HDR + HEVC/VP9/AV1 PQ decode) + SDR ramp.

  • Color reference card

    Standard sRGB swatches on neutral gray: look for color casts in the grayscale, oversaturated primaries, and unnatural skin tones. A visual reference — pair with a hardware colorimeter for real calibration.

    Static — labelled grayscale steps, primaries/secondaries, skin & memory colors.

  • Burn-in / retention detection

    On each solid field, look for faint ghosts of previous content (OLED burn-in) or temporary shadows that fade (LCD image retention) — a healthy panel shows a perfectly uniform field with nothing underneath.

    Click / space to step gray & color fields; Auto-cycle leaves it running.

About this tool

This display test has two halves. The info panel reads out what your screen actually is: physical vs CSS resolution and pixel ratio, color depth, wide-gamut support (sRGB / P3 / Rec.2020), HDR capability, and the real refresh rate measured live from frame timestamps — often revealing that a "144 Hz" laptop panel is running at 60 Hz. The test patterns then let you inspect the panel itself, full-screen, one click at a time.

The patterns cover the checks reviewers and buyers actually run: solid-color cycles for dead and stuck pixels, pure black and white for backlight bleed and uniformity, per-channel gradients that make 8-bit banding visible, a gamma chart, a moving-object test for ghosting and motion clarity, text samples for sharpness at your scaling settings, and a multi-touch pad for touchscreens. Every pattern comes with a one-line guide on what to look for and what a healthy screen should show — most test sites give you the image and leave you guessing.

It's all generated in your browser with canvas and SVG — nothing to download or install, which makes it ideal for checking a new monitor before the return window closes, verifying a second-hand screen at handover, or diagnosing a panel that suddenly looks wrong.

Three more patterns go deeper. An HDR capability matrix feature-detects both halves of the equation — whether your display reports HDR and whether this browser can actually decode HEVC, VP9 and AV1 in their 10-bit PQ (Rec.2020) HDR configurations — because a screen can advertise HDR while the browser silently falls back to SDR decode, and vice versa; on an HDR display it adds a near-white ramp for checking highlight separation. A color reference card lays out standard sRGB swatches — labelled grayscale steps, primaries and secondaries, skin tones and memory colors — on a neutral gray surround, to eye-ball color casts before reaching for a colorimeter. And a dedicated burn-in / image-retention set runs solid 25/50/75% grays plus full color fields, with an auto-cycle mode you can leave running to reveal OLED burn-in or LCD retention.

Frequently asked questions

How do I check for dead pixels?

Run the solid-color cycle full-screen and step through black, white, red, green and blue with a click or the space bar. A pixel that stays black on every color is dead; one stuck on a single color shows up on the complementary screens. Wipe the screen first — dust is the classic false positive.

Can a stuck pixel be fixed?

Sometimes. Dead (always black) pixels are usually permanent hardware faults, but stuck subpixels occasionally recover after rapid color cycling or gentle massage with a soft cloth. Check your monitor's dead-pixel warranty policy — many manufacturers replace panels over a threshold.

Why does the measured refresh rate differ from my monitor's spec?

The test measures real frames delivered to the browser window. Common reasons for a lower number: the OS display setting is at 60 Hz, the window sits on a lower-Hz screen in a multi-monitor setup, a power-saving mode is throttling, or the browser is capping animation. It measures the screen the window is currently on.

What is backlight bleed and how much is normal?

On the pure-black pattern in a dark room, LCD backlight leaking around edges/corners shows as brighter patches. Almost every LCD has some; it's a defect when clearly visible at normal brightness during dark content. OLED panels show none (each pixel emits its own light).

Does the test work for HDR and wide color gamut?

The info panel detects whether your display and browser advertise HDR (dynamic-range: high) and which gamut is covered (sRGB, Display-P3, Rec.2020). The dedicated HDR pattern goes further: it feature-detects HDR video decode for HEVC, VP9 and AV1 in their 10-bit PQ configurations via the MediaCapabilities API, and on an HDR display adds a near-white ramp for a subjective highlight-separation check.

Why isn't there a real HDR video clip to play?

A genuine HDR10 sample that exercises peak-brightness headroom needs a multi-megabyte HEVC/AV1 file plus codec support that varies by browser, and a 2D canvas physically can't emit a true PQ signal — so rather than fake it, the HDR pattern gives you an honest capability matrix (display HDR plus per-codec decode support) and an SDR-bounded ramp. The matrix tells you whether HDR playback would work; it just doesn't ship the clip.

How do I check for OLED burn-in or LCD image retention?

Run the burn-in pattern full-screen and step through the solid 25/50/75% grays and full color fields — faint ghosts of previously displayed content (taskbars, logos) that persist are OLED burn-in; temporary shadows on LCDs that fade after a minute are image retention, usually harmless. Auto-cycle mode leaves the fields rotating so you can also use it to help even out mild retention.

Is the color reference card a substitute for a colorimeter?

No — and it says so. It's a labelled visual reference: standard sRGB grayscale steps, primaries/secondaries, skin tones and memory colors on a neutral gray surround, useful for spotting obvious color casts, oversaturation or crushed shadows by eye. True calibration still needs a hardware colorimeter (a Spyder, ColorMunki, etc. with software like DisplayCAL) measuring the panel directly.