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Glossary
Screen resolution
Screen resolution is the size of your display as a page reads it, in layout points rather than in physical pixels.
What a site reads off the screen
A page never sees your monitor. It sees four numbers the browser reports about it, and a fifth number about the window you opened.
The size
Width and height in layout points. This is the reading people mean by resolution, and it is the coarsest of the five.
The usable area
The same size minus the bar the desktop keeps for itself. The difference states which system you are on.
The pixel ratio
How many device pixels go into one layout point. Multiplied by the size it names the physical panel.
The colour depth
Bits per pixel. Almost every machine answers the same here, which makes any other answer loud.
The window
The inner size of the page area, which changes as you resize and is more specific than the screen behind it.
Your screen right now
These values are read in your browser on this page. Nothing leaves it and no request goes out with the reading.
Makineniz, şu anda
- Screen size
- makinenizde ölçülüyor
- Usable area
- makinenizde ölçülüyor
- Device pixel ratio
- makinenizde ölçülüyor
- Colour depth
- makinenizde ölçülüyor
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Where the contradictions show up
An edited size is easy. Keeping it from arguing with the four readings around it is the part that decides whether the profile holds.
A window wider than its screen
No device can open a window larger than the display it claims to have, and the comparison is one line of page code.
A size and ratio that multiply to nothing
A claimed panel that nobody manufactures is as readable as a wrong size, and on Windows the two numbers multiply exactly.
Portrait sizes with landscape orientation
A phone taller than it is wide reporting a sideways orientation is a device arguing with itself.
A usable area above the screen
The area left after the system bar cannot be larger than the screen it was taken from.
What our engine does
All five readings arrive as one seed on the launch line, before the first line of page code runs. The size comes from panels that machines of that platform really report.
The usable height is the screen minus the bar that system draws, and on a phone there is no bar, so the two are equal. The pixel ratio is drawn from those possible for the size that fell to the profile.
- 1
The pair is kept together
A hand-picked ratio that does not fit the chosen size is refused when you save, and the field that was refused is named.
- 2
A mobile profile gets the window too
The window is brought to the size of the device, and every new tab is held until that size is set.
- 3
The set stays with the profile
The same profile reads the same screen on every launch, because the numbers are derived rather than stored.
What the shipping build answers
Three measurements rather than three claims. The first comes from the acceptance run of the build shipping today, on a Windows profile.
The size matched the seed
Measured on a build host whose own display is nothing like the one the profile claims.
1280x720A phone window fits its own device
A desktop engine keeps windows above five hundred points wide, so the size is set through the debugging protocol instead.
360x800No screen decides the rest
Across four hundred profiles every screen size occurs with more than one graphics card, so the size alone links nothing.
many cards per size
How to check your own
The panel above shows what this browser reports. The free check on this site adds the pixel ratio and the colour depth on the same row.
Inside the app the self-test runs in a profile against the engine that profile launched, and the mobile lines also compare the window to the screen.
What this does not do
- It does not resize the window of a desktop profile. That window is as large as you make it, and a window wider than the claimed screen is a contradiction a page reads in one line.
- It does not give you a display nobody else has. The sizes are ones real machines report, because a size no one else reports is a mark of its own.
- It does not change what your monitor really is. The operating system, your screenshots and every other program still see the panel you bought.
- It does not undo a link that already exists. Two accounts opened from one profile stay linked whatever the screen says afterwards.
Check it
Every number above comes from a file you can open.
- The screen checks the self-test runs
- apps/desktop/src/lib/fpAudit.js
- Where the size and the ratio come from
- packages/shared/src/index.js
- The window of a mobile profile
- apps/desktop/src/lib/mobileEmulation.js · apps/desktop/src/lib/mobileWindow.js
- The parts have to agree with each other
- apps/desktop/test/fingerprint-consistency.js · apps/desktop/test/mobile-really-mobile.js
Questions
- Is my screen size enough to identify me?
- On its own, no: common sizes are shared by millions of machines. It becomes useful to a site next to the pixel ratio, the fonts, the core count and the memory figure.
- Does browser zoom change these readings?
- Zoom changes the window and the pixel ratio, not the screen size. In a profile the ratio comes from the seed, so zooming does not move it either.
- Why does the usable area matter?
- Because the gap between it and the screen is the height of the system bar, and that height differs from system to system. A phone has no bar at all.
- Do two profiles get two screens?
- Yes. The size, the ratio and the usable area are all derived from the profile seed, and one size never decides the rest of the machine.
See what your own profile answers
The self-test runs inside a profile and shows all 29 measurements, green and red alike.