This page does some feature detection and decides that we are not a compatible WebGL context. This only reproduces with WebGL 2 enabled. I traced it a bit, but didn't quite track it down to a particular piece of logic. It uses PixiJS, but I'm not sure if that's the code which is failing.
<rdar://problem/73776401>
This is the actual radar: rdar://problem/67756671
In DevTools, after clicking the "+" button to start the camera: photobooth - eventshare.co, source file jeelizFaceFilter.js: Against a WebGL2RenderingContext: It looks for ["EXT_color_buffer_float", "WEBGL_color_buffer_float", "OES_color_buffer_float"] (succeeds with EXT_color_buffer_float) then for ["EXT_color_buffer_half_float", "WEBGL_color_buffer_half_float", "OES_color_buffer_half_float"] (succeeds with EXT_color_buffer_half_float) then for ["OES_texture_float", "MOZ_OES_texture_float", "WEBKIT_OES_texture_float"] (fails) then for ["OES_texture_float_linear", "MOZ_OES_texture_float_linear", "WEBKIT_OES_texture_float_linear"] (succeeds) then for ["OES_texture_half_float", "MOZ_OES_texture_half_float", "WEBKIT_OES_texture_half_float"] (fails) then for ["OES_texture_half_float_linear", "MOZ_OES_texture_half_float_linear", "WEBKIT_OES_texture_half_float_linear"] (fails) then for ["OES_texture_half_float", "MOZ_OES_texture_half_float", "WEBKIT_OES_texture_half_float"] (fails) then for ["EXT_color_buffer_float", "WEBGL_color_buffer_float", "OES_color_buffer_float"] (succeeds with EXT_color_buffer_float) then for ["EXT_color_buffer_half_float", "WEBGL_color_buffer_half_float", "OES_color_buffer_half_float"] (succeeds with EXT_color_buffer_half_float) then for ["OES_texture_float", "MOZ_OES_texture_float", "WEBKIT_OES_texture_float"] (fails) then for ["OES_texture_float_linear", "MOZ_OES_texture_float_linear", "WEBKIT_OES_texture_float_linear"] (succeeds) then for ["OES_texture_half_float", "MOZ_OES_texture_half_float", "WEBKIT_OES_texture_half_float"] (fails) then for ["OES_texture_half_float_linear", "MOZ_OES_texture_half_float_linear", "WEBKIT_OES_texture_half_float_linear"] (fails) then for ["OES_texture_half_float", "MOZ_OES_texture_half_float", "WEBKIT_OES_texture_half_float"] (fails) then for ["OES_texture_float", "MOZ_OES_texture_float", "WEBKIT_OES_texture_float"] (fails) ... Chrome returns null for EXT_color_buffer_half_float Chrome also returns null for OES_texture_half_float_linear (subsumed into WebGL 2.0) My best guess is that the presence of EXT_color_buffer_half_float - which we added as a concession to iOS - is confusing their code. Have you tried commenting out WebKit's advertising of that extension?