Which source did the browser pick?

Mount Hood, snow-covered, reflected in a still lake ringed by dark evergreen forest under a pale lavender sky.
Photograph: Lake Mountain Landscape, Bonnie Moreland, CC0.

What the browser knew

Viewport
needs JavaScript
devicePixelRatio
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Slot from sizes
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Pixels needed
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What it chose

currentSrc
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File width
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Laid out at
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The candidates in the chosen format
FileWidthBytes