diff --git a/src/js/media-airplay-button.js b/src/js/media-airplay-button.js
index 30da6024e..b362b4082 100644
--- a/src/js/media-airplay-button.js
+++ b/src/js/media-airplay-button.js
@@ -2,6 +2,7 @@ import MediaChromeButton from './media-chrome-button.js';
 import { window, document } from './utils/server-safe-globals.js';
 import { MediaUIEvents, MediaUIAttributes } from './constants.js';
 import { verbs } from './labels/labels.js';
+import { getStringAttr, setStringAttr } from './utils/element-utils.js';
 
 const airplayIcon = `<svg aria-hidden="true" viewBox="0 0 26 24">
   <path d="M22.13 3H3.87a.87.87 0 0 0-.87.87v13.26a.87.87 0 0 0 .87.87h3.4L9 16H5V5h16v11h-4l1.72 2h3.4a.87.87 0 0 0 .87-.87V3.87a.87.87 0 0 0-.86-.87Zm-8.75 11.44a.5.5 0 0 0-.76 0l-4.91 5.73a.5.5 0 0 0 .38.83h9.82a.501.501 0 0 0 .38-.83l-4.91-5.73Z"/>
@@ -39,6 +40,17 @@ class MediaAirplayButton extends MediaChromeButton {
     super.connectedCallback();
   }
 
+  /**
+   * @type {string | undefined} Airplay unavailability state
+   */
+  get mediaAirplayUnavailable() {
+    return getStringAttr(this, MediaUIAttributes.MEDIA_AIRPLAY_UNAVAILABLE);
+  }
+
+  set mediaAirplayUnavailable(value) {
+    setStringAttr(this, MediaUIAttributes.MEDIA_AIRPLAY_UNAVAILABLE, value);
+  }
+
   handleClick() {
     const evt = new window.CustomEvent(MediaUIEvents.MEDIA_AIRPLAY_REQUEST, {
       composed: true,
diff --git a/src/js/media-captions-button.js b/src/js/media-captions-button.js
index b130e4922..0f67627a1 100644
--- a/src/js/media-captions-button.js
+++ b/src/js/media-captions-button.js
@@ -2,7 +2,12 @@ import MediaChromeButton from './media-chrome-button.js';
 import { window, document } from './utils/server-safe-globals.js';
 import { MediaUIAttributes } from './constants.js';
 import { nouns } from './labels/labels.js';
-import { areSubsOn, toggleSubsCaps } from './utils/captions.js';
+import {
+  areSubsOn,
+  parseTextTracksStr,
+  stringifyTextTrackList,
+  toggleSubsCaps,
+} from './utils/captions.js';
 
 const ccIconOn = `<svg aria-hidden="true" viewBox="0 0 26 24">
   <path d="M22.83 5.68a2.58 2.58 0 0 0-2.3-2.5c-3.62-.24-11.44-.24-15.06 0a2.58 2.58 0 0 0-2.3 2.5c-.23 4.21-.23 8.43 0 12.64a2.58 2.58 0 0 0 2.3 2.5c3.62.24 11.44.24 15.06 0a2.58 2.58 0 0 0 2.3-2.5c.23-4.21.23-8.43 0-12.64Zm-11.39 9.45a3.07 3.07 0 0 1-1.91.57 3.06 3.06 0 0 1-2.34-1 3.75 3.75 0 0 1-.92-2.67 3.92 3.92 0 0 1 .92-2.77 3.18 3.18 0 0 1 2.43-1 2.94 2.94 0 0 1 2.13.78c.364.359.62.813.74 1.31l-1.43.35a1.49 1.49 0 0 0-1.51-1.17 1.61 1.61 0 0 0-1.29.58 2.79 2.79 0 0 0-.5 1.89 3 3 0 0 0 .49 1.93 1.61 1.61 0 0 0 1.27.58 1.48 1.48 0 0 0 1-.37 2.1 2.1 0 0 0 .59-1.14l1.4.44a3.23 3.23 0 0 1-1.07 1.69Zm7.22 0a3.07 3.07 0 0 1-1.91.57 3.06 3.06 0 0 1-2.34-1 3.75 3.75 0 0 1-.92-2.67 3.88 3.88 0 0 1 .93-2.77 3.14 3.14 0 0 1 2.42-1 3 3 0 0 1 2.16.82 2.8 2.8 0 0 1 .73 1.31l-1.43.35a1.49 1.49 0 0 0-1.51-1.21 1.61 1.61 0 0 0-1.29.58A2.79 2.79 0 0 0 15 12a3 3 0 0 0 .49 1.93 1.61 1.61 0 0 0 1.27.58 1.44 1.44 0 0 0 1-.37 2.1 2.1 0 0 0 .6-1.15l1.4.44a3.17 3.17 0 0 1-1.1 1.7Z"/>
@@ -13,15 +18,14 @@ const ccIconOff = `<svg aria-hidden="true" viewBox="0 0 26 24">
 </svg>`;
 
 const slotTemplate = document.createElement('template');
-slotTemplate.innerHTML = /*html*/`
+slotTemplate.innerHTML = /*html*/ `
   <style>
   :host([aria-checked="true"]) slot:not([name=on]) > *,
   :host([aria-checked="true"]) ::slotted(:not([slot=on])) {
     display: none !important;
   }
 
-  ${/* Double negative, but safer if display doesn't equal 'block' */ ''
-  }
+  ${/* Double negative, but safer if display doesn't equal 'block' */ ''}
   :host(:not([aria-checked="true"])) slot:not([name=off]) > *,
   :host(:not([aria-checked="true"])) ::slotted(:not([slot=off])) {
     display: none !important;
@@ -36,12 +40,43 @@ const updateAriaChecked = (el) => {
   el.setAttribute('aria-checked', areSubsOn(el));
 };
 
+/**
+ * @param {any} el Should be HTMLElement but issues with window shim
+ * @param {string} attrName
+ * @returns {Array<Object>} An array of TextTrack-like objects.
+ */
+const getSubtitlesListAttr = (el, attrName) => {
+  const attrVal = el.getAttribute(attrName);
+  return attrVal ? parseTextTracksStr(attrVal) : [];
+};
+
+/**
+ *
+ * @param {any} el Should be HTMLElement but issues with window shim
+ * @param {string} attrName
+ * @param {Array<Object>} list An array of TextTrack-like objects
+ */
+const setSubtitlesListAttr = (el, attrName, list) => {
+  // null, undefined, and empty arrays are treated as "no value" here
+  if (!list) {
+    el.removeAttribute(attrName);
+    return;
+  }
+
+  // don't set if the new value is the same as existing
+  const newValStr = stringifyTextTrackList(list);
+  const oldValStr = stringifyTextTrackList(el.getAttribute(attrName) ?? '');
+  if (oldValStr === newValStr) return;
+
+  el.setAttribute(attrName, newValStr);
+};
+
 /**
  * @slot on - An element that will be shown while closed captions or subtitles are on.
  * @slot off - An element that will be shown while closed captions or subtitles are off.
  *
  * @attr {string} mediasubtitleslist - (read-only) A list of all subtitles and captions.
- * @attr {boolean} mediasubtitlesshowing - (read-only) A list of the showing subtitles and captions.
+ * @attr {string} mediasubtitlesshowing - (read-only) A list of the showing subtitles and captions.
  *
  * @cssproperty [--media-captions-button-display = inline-flex] - `display` property of button.
  */
@@ -76,6 +111,33 @@ class MediaCaptionsButton extends MediaChromeButton {
     super.attributeChangedCallback(attrName, oldValue, newValue);
   }
 
+  /**
+   * @type {Array<object>} An array of TextTrack-like objects.
+   * Objects must have the properties: kind, language, and label.
+   */
+  get mediaSubtitlesList() {
+    return getSubtitlesListAttr(this, MediaUIAttributes.MEDIA_SUBTITLES_LIST);
+  }
+
+  set mediaSubtitlesList(list) {
+    setSubtitlesListAttr(this, MediaUIAttributes.MEDIA_SUBTITLES_LIST, list);
+  }
+
+  /**
+   * @type {Array<object>} An array of TextTrack-like objects.
+   * Objects must have the properties: kind, language, and label.
+   */
+  get mediaSubtitlesShowing() {
+    return getSubtitlesListAttr(
+      this,
+      MediaUIAttributes.MEDIA_SUBTITLES_SHOWING
+    );
+  }
+
+  set mediaSubtitlesShowing(list) {
+    setSubtitlesListAttr(this, MediaUIAttributes.MEDIA_SUBTITLES_SHOWING, list);
+  }
+
   handleClick() {
     toggleSubsCaps(this);
   }
diff --git a/src/js/media-cast-button.js b/src/js/media-cast-button.js
index dbdd93037..a0e726fdd 100644
--- a/src/js/media-cast-button.js
+++ b/src/js/media-cast-button.js
@@ -2,13 +2,19 @@ import MediaChromeButton from './media-chrome-button.js';
 import { window, document } from './utils/server-safe-globals.js';
 import { MediaUIEvents, MediaUIAttributes } from './constants.js';
 import { verbs } from './labels/labels.js';
+import {
+  getBooleanAttr,
+  setBooleanAttr,
+  getStringAttr,
+  setStringAttr,
+} from './utils/element-utils.js';
 
 const enterIcon = `<svg aria-hidden="true" viewBox="0 0 24 24"><g><path class="cast_caf_icon_arch0" d="M1,18 L1,21 L4,21 C4,19.3 2.66,18 1,18 L1,18 Z"/><path class="cast_caf_icon_arch1" d="M1,14 L1,16 C3.76,16 6,18.2 6,21 L8,21 C8,17.13 4.87,14 1,14 L1,14 Z"/><path class="cast_caf_icon_arch2" d="M1,10 L1,12 C5.97,12 10,16.0 10,21 L12,21 C12,14.92 7.07,10 1,10 L1,10 Z"/><path class="cast_caf_icon_box" d="M21,3 L3,3 C1.9,3 1,3.9 1,5 L1,8 L3,8 L3,5 L21,5 L21,19 L14,19 L14,21 L21,21 C22.1,21 23,20.1 23,19 L23,5 C23,3.9 22.1,3 21,3 L21,3 Z"/></g></svg>`;
 
 const exitIcon = `<svg aria-hidden="true" viewBox="0 0 24 24"><g><path class="cast_caf_icon_arch0" d="M1,18 L1,21 L4,21 C4,19.3 2.66,18 1,18 L1,18 Z"/><path class="cast_caf_icon_arch1" d="M1,14 L1,16 C3.76,16 6,18.2 6,21 L8,21 C8,17.13 4.87,14 1,14 L1,14 Z"/><path class="cast_caf_icon_arch2" d="M1,10 L1,12 C5.97,12 10,16.0 10,21 L12,21 C12,14.92 7.07,10 1,10 L1,10 Z"/><path class="cast_caf_icon_box" d="M21,3 L3,3 C1.9,3 1,3.9 1,5 L1,8 L3,8 L3,5 L21,5 L21,19 L14,19 L14,21 L21,21 C22.1,21 23,20.1 23,19 L23,5 C23,3.9 22.1,3 21,3 L21,3 Z"/><path class="cast_caf_icon_boxfill" d="M5,7 L5,8.63 C8,8.6 13.37,14 13.37,17 L19,17 L19,7 Z"/></g></svg>`;
 
 const slotTemplate = document.createElement('template');
-slotTemplate.innerHTML = /*html*/`
+slotTemplate.innerHTML = /*html*/ `
   <style>
   :host([${MediaUIAttributes.MEDIA_IS_CASTING}]) slot:not([name=exit]) > *,
   :host([${MediaUIAttributes.MEDIA_IS_CASTING}]) ::slotted(:not([slot=exit])) {
@@ -16,8 +22,12 @@ slotTemplate.innerHTML = /*html*/`
   }
 
   ${/* Double negative, but safer if display doesn't equal 'block' */ ''}
-  :host(:not([${MediaUIAttributes.MEDIA_IS_CASTING}])) slot:not([name=enter]) > *,
-  :host(:not([${MediaUIAttributes.MEDIA_IS_CASTING}])) ::slotted(:not([slot=enter])) {
+  :host(:not([${
+    MediaUIAttributes.MEDIA_IS_CASTING
+  }])) slot:not([name=enter]) > *,
+  :host(:not([${
+    MediaUIAttributes.MEDIA_IS_CASTING
+  }])) ::slotted(:not([slot=enter])) {
     display: none !important;
   }
   </style>
@@ -27,11 +37,8 @@ slotTemplate.innerHTML = /*html*/`
 `;
 
 const updateAriaLabel = (el) => {
-  const isCast =
-    el.getAttribute(MediaUIAttributes.MEDIA_IS_CASTING) != null;
-  const label = isCast
-    ? verbs.EXIT_CAST()
-    : verbs.ENTER_CAST();
+  const isCast = el.getAttribute(MediaUIAttributes.MEDIA_IS_CASTING) != null;
+  const label = isCast ? verbs.EXIT_CAST() : verbs.ENTER_CAST();
   el.setAttribute('aria-label', label);
 };
 
@@ -69,9 +76,31 @@ class MediaCastButton extends MediaChromeButton {
     super.attributeChangedCallback(attrName, oldValue, newValue);
   }
 
+  /**
+   * @type {boolean} Are we currently casting
+   */
+  get mediaIsCasting() {
+    return getBooleanAttr(this, MediaUIAttributes.MEDIA_IS_CASTING);
+  }
+
+  set mediaIsCasting(value) {
+    setBooleanAttr(this, MediaUIAttributes.MEDIA_IS_CASTING, value);
+  }
+
+  /**
+   * @type {string | undefined} Cast unavailability state
+   */
+  get mediaCastUnavailable() {
+    return getStringAttr(this, MediaUIAttributes.MEDIA_CAST_UNAVAILABLE);
+  }
+
+  set mediaCastUnavailable(value) {
+    setStringAttr(this, MediaUIAttributes.MEDIA_CAST_UNAVAILABLE, value);
+  }
+
   handleClick() {
     const eventName =
-      this.getAttribute(MediaUIAttributes.MEDIA_IS_CASTING) != null
+      this.mediaIsCasting != null
         ? MediaUIEvents.MEDIA_EXIT_CAST_REQUEST
         : MediaUIEvents.MEDIA_ENTER_CAST_REQUEST;
     this.dispatchEvent(
diff --git a/src/js/utils/element-utils.js b/src/js/utils/element-utils.js
index ea74b31d5..63506a136 100644
--- a/src/js/utils/element-utils.js
+++ b/src/js/utils/element-utils.js
@@ -112,7 +112,6 @@ export function getBooleanAttr(el, attrName) {
 }
 
 /**
- *
  * @param {any} el (Should be an HTMLElement, but need any for SSR cases)
  * @param {string} attrName
  * @param {boolean} value
@@ -129,3 +128,29 @@ export function setBooleanAttr(el, attrName, value) {
 
   el.toggleAttribute(attrName, value);
 }
+
+/**
+ * @param {any} el (Should be an HTMLElement, but need any for SSR cases)
+ * @param {string} attrName
+ */
+export function getStringAttr(el, attrName) {
+  return el.getAttribute(attrName) ?? undefined;
+}
+
+/**
+ * @param {*} el (Should be an HTMLElement, but need any for SSR cases)
+ * @param {string} attrName
+ * @param {string} value
+ */
+export function setStringAttr(el, attrName, value) {
+  // avoid triggering a set if no change
+  if (getStringAttr(el, attrName) == value) return;
+
+  // also handles undefined
+  if (value == null) {
+    el.removeAttribute(attrName);
+    return;
+  }
+
+  el.setAttribute(attrName, `${value}`);
+}