<p>I deliberately used a whitelist, after some consideration.</p>
<p>You of course correct that it's impossible to know the set of browsers that don't need it. It's equally impossible to know the set that do however, and as the polyfills do nothing when not needed I decided it was safer to err on the side of caution and send them when they might be needed - not sending them is basically just a performance optimisation.</p>
<p>I would also suggest that a substantial proportion of "other browsers" that would count as modern enough are in fact WebKit based anyway and would therefore be covered by this whitelist unless they mask that fact from their user agent.</p>

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