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> It's not that easy to "present a fingerprint" without compromising the user experience. And that's exactly what I'm talking about. > what about things like

> It's not that easy to "present a fingerprint" without compromising the user experience. And that's exactly what I'm talking about. > what about things like viewport size and font rendering? Not much can be done about viewport size, but a browser could easily ship with 2 fonts (one serif and one sans serif) and only allow access to those.

derefr 4y ago
“Font rendering” is a different thing than “what fonts you have.” Font rendering is about how fonts are drawn to the screen. The trick is to draw some words to a <canvas> and then pixel-peep the result. Different OSes and browsers use different font renderers and font hinting logic; fonts will even render differently on a different-DPI screen.
- grishka 4y ago
  Not just the <canvas>. The font rendering of the underlying platform also influences the width of strings. So if you create a <span> with some text, its width will differ several pixels depending on the host OS.
- GoblinSlayer 4y ago
  Don't they already use freetype to parse webfonts?
  - derefr 4y ago
    Is that a standard — that all browsers are forced to use the Freetype library, or to be bug-for-bug compatible with its glyph+hint parsing semantics? I've never heard of anything like that. But also, even if they did, AFAIK browsers still mostly lean on OS text-drawing APIs for font rendering. Text in Chrome on Windows looks different than text in Chrome on macOS, etc. The same pile of beziers, and the same pile of hints, converts into a different set of hinted pixels (and sub-pixels!) when fed to each OS text-drawing API. Especially when those APIs are configured by user settings around subpixel hinting / "font smoothing", and when those APIs are aware of the device being rendered to and so render subpixels differently for high-DPI vs low-DPI screens, RGB vs BGR displays, etc.
- account42 4y ago
  Different browsersare always distinguishable but a single browser could choose to always use the same font rendering code and settings, at least for private browsing.

derefr 4y ago

“Font rendering” is a different thing than “what fonts you have.” Font rendering is about how fonts are drawn to the screen. The trick is to draw some words to a <canvas> and then pixel-peep the result. Different OSes and browsers use different font renderers and font hinting logic; fonts will even render differently on a different-DPI screen.

grishka 4y ago
Not just the <canvas>. The font rendering of the underlying platform also influences the width of strings. So if you create a <span> with some text, its width will differ several pixels depending on the host OS.
GoblinSlayer 4y ago
Don't they already use freetype to parse webfonts?
- derefr 4y ago
  Is that a standard — that all browsers are forced to use the Freetype library, or to be bug-for-bug compatible with its glyph+hint parsing semantics? I've never heard of anything like that. But also, even if they did, AFAIK browsers still mostly lean on OS text-drawing APIs for font rendering. Text in Chrome on Windows looks different than text in Chrome on macOS, etc. The same pile of beziers, and the same pile of hints, converts into a different set of hinted pixels (and sub-pixels!) when fed to each OS text-drawing API. Especially when those APIs are configured by user settings around subpixel hinting / "font smoothing", and when those APIs are aware of the device being rendered to and so render subpixels differently for high-DPI vs low-DPI screens, RGB vs BGR displays, etc.
account42 4y ago
Different browsersare always distinguishable but a single browser could choose to always use the same font rendering code and settings, at least for private browsing.