--- /dev/null
+/* @flow */
+"use strict";
+
+const keywordSets = require("../reference/keywordSets");
+
+/**
+ * Check whether a string is a keyframe selector.
+ */
+module.exports = function(selector /*: string*/) /*: boolean*/ {
+ if (keywordSets.keyframeSelectorKeywords.has(selector)) {
+ return true;
+ }
+
+ // Percentages
+ if (/^(?:\d+\.?\d*|\d*\.?\d+)%$/.test(selector)) {
+ return true;
+ }
+
+ return false;
+};