If you load a NULL shader using base64 the implementation will ASSERT when it creates the compiled programs. -webkit-filter: custom(url(data:text/plain;base64,)) Source/WebCore/platform/graphics/filters/CustomFilterProgramInfo.cpp(75) : WebCore::CustomFilterProgramInfo::CustomFilterProgramInfo(const WTF::String&, const WTF::String&, WebCore::CustomFilterProgramType, const WebCore::CustomFilterProgramMixSettings&, WebCore::CustomFilterMeshType)