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<h2>Fullscreen with JavaScript</h2>
<p>Click on the "Open Fullscreen" button to open this page in fullscreen mode. Close it by either clicking the "Esc" key on your keyboard, or with the "Close Fullscreen" button.</p>

<button onclick="openFullscreen();">Open Fullscreen</button>
<button onclick="closeFullscreen();">Close Fullscreen</button>

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<!DOCTYPE html><html><head><meta name="viewport" content="width=device-width, initial-scale=1"></head><body>​<h2>Fullscreen with JavaScript</h2><p>Click on the "Open Fullscreen" button to open this page in fullscreen mode. Close it by either clicking the "Esc" key on your keyboard, or with the "Close Fullscreen" button.</p>​<button onclick="openFullscreen();">Open Fullscreen</button><button onclick="closeFullscreen();">Close Fullscreen</button>​<script>var elem = document.documentElement;function openFullscreen() {  if (elem.requestFullscreen) {    elem.requestFullscreen();  } else if (elem.webkitRequestFullscreen) { /* Safari */    elem.webkitRequestFullscreen();  } else if (elem.msRequestFullscreen) { /* IE11 */    elem.msRequestFullscreen();  }}​function closeFullscreen() {  if (document.exitFullscreen) {    document.exitFullscreen();  } else if (document.webkitExitFullscreen) { /* Safari */    document.webkitExitFullscreen();  } else if (document.msExitFullscreen) { /* IE11 */    document.msExitFullscreen();  }}</script>​</body></html>​​