Select platform: [HTML5](https://developers.google.com/ad-manager/dynamic-ad-insertion/sdk/html5/snapback "View this page for the HTML5 platform docs.") [Android](https://developers.google.com/ad-manager/dynamic-ad-insertion/sdk/android/snapback "View this page for the Android platform docs.") [iOS](https://developers.google.com/ad-manager/dynamic-ad-insertion/sdk/ios/snapback "View this page for the iOS platform docs.") [tvOS](https://developers.google.com/ad-manager/dynamic-ad-insertion/sdk/tvos/snapback "View this page for the tvOS platform docs.") [Roku](https://developers.google.com/ad-manager/dynamic-ad-insertion/sdk/roku/snapback "View this page for the Roku platform docs.")

<br />

As a video publisher, you may want to prevent your viewers from
seeking past your mid-roll ads. When a user seeks past an ad break,
you can take them back to the start of that ad break, and then return
them to their seek location after that ad break has completed. This
feature is called "snapback."

As an example, see the diagram below. Your viewer is watching a video,
and decides to seek from the 5-minute mark to the 15-minute mark.
There is, however, an ad break at the 10-minute mark that you want
them to watch before they can watch the content after it:

![](https://developers.google.com/static/interactive-media-ads/images/dai_snapback1.png)

In order to show this ad break, take the following steps:

1. Check if the user ran a seek that jumped past an unwatched ad break, and if so, take them back to the ad break.
2. After the ad break completes, return them to their original seek.

In diagram form, that looks like this:

![](https://developers.google.com/static/interactive-media-ads/images/dai_snapback2.png)

Here's how to implement snapback using the IMA DAI SDK, as demonstrated in
[Advanced Example](https://github.com/googleads/googleads-ima-html5-dai/tree/master/hls_js/advanced).

## Prevent a seek from leaving an ad break unwatched

Check if the user has run a seek that went past an unwatched ad break,
and if so, take them back to the ad break.
In the HTML5 SDK, set an event listener on the content player's `seeked` event
to trigger `onSeekEnd()`. That method (presented below) checks the cue point
prior to the user's seek time. If it is unplayed, seek to the beginning of that
ad break instead of their initial desired seek point, and save that desired
seek point in `snapForwardTime`.

    function onSeekEnd() {
      if (isLiveStream) { return; }
      if (isSnapback) {
        isSnapback = false;
        return;
      }
      var currentTime = videoElement.currentTime;
      var previousCuePoint =
          streamManager.previousCuePointForStreamTime(currentTime);
      if (previousCuePoint && !previousCuePoint.played) {
        isSnapback = true;
        snapForwardTime = currentTime;
        videoElement.currentTime = previousCuePoint.start;
    }

## Put the user back to their original seek

Now when you get an `AD_BREAK_ENDED` event, check to see if `snapForwardTime`
is set. If so, take the user to that point in the stream, because the ad
break they just watched was the result of snapback:

    function onAdBreakEnded(e) {
      videoElement.controls = true;
      clickElement.style.display = 'none';
      adUiDiv.style.display = 'none';
      if (snapForwardTime && snapForwardTime > videoElement.currentTime) {
        videoElement.currentTime = snapForwardTime;
        snapForwardTime = null;
      }
    }