},
/**
- * Get an automatically generated random ID (persisted in sessionStorage)
+ * Retrieve a random ID persisted in sessionStorage, generating it if needed
*
- * This ID is ephemeral for everyone, staying in their browser only until they
- * close their browsing session.
+ * This ID is stored in sessionStorage and persists within a single tab,
+ * including between page views through links and form submissions,
+ * and when going forwards/backwards in browser history, and when restoring
+ * a closed tab, or restoring a closed browser session.
+ *
+ * This is different from session cookies, because it is not shared between
+ * tabs of the same browser. Two simultaneous pageviews in the same browser
+ * can have different session IDs. The ID is also not re-used when opening
+ * a new tab to a website after fully closing others.
+ *
+ * See https://phabricator.wikimedia.org/T118063#4547178 and
+ * https://developer.mozilla.org/en-US/docs/Web/API/Window/sessionStorage
+ * for more information.
*
* @return {string} Random session ID
*/