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Client Side Ad Insertion

Published Date: 15 March 2023

What is Client Side Ad Insertion(CSAI)?

The method used by Video Players for delivering personalized advertisements, tailored according to previously collected data, in audiovisual content is called Client Side Ad Insertion. The Video Player requests the ad server to play an advertisement when the video reaches ad markers during playback.

How does CSAI work?

  1. Before streaming the digital content, the video player should download the manifest from CDN.
  2. Preroll advertisements will start playing before the video starts.
  3. The fragment will be paused when the video reaches a specific ad marker.
  4. The Video Player will then issue an API call as a request to the server.
  5. The server will respond with a VAST tag which comprises all the information related to the advertisement.
  6. The Video Player reads the information and streams the advertisement.
  7. After completion, the video continues from the point where it was paused before the advertisement.

Advantages of Client-Side Ad Insertion

  • Highly compatible; can support different kinds of ads, including skippable, clickable, and closable ads.
  • Useful for tracking and analyzing various ad-related performance metrics.
  • Freedom for video publishers and advertisers to leverage different ad formats like surveys, click-throughs, and overlays.
  • It can function with as well as without ad markers.
  • Can track user data and activity to personalize their advertisement experience.

Disadvantages of Client-Side Ad Insertion

  • The video player requests the ad server for a relevant advertisement and then waits for it to be processed, causing significant latency issues.
  • Complications related to bitstream can lead to buffering.
  • CSAI is highly prone to ad blockers, leading to significant loss of revenue for publishers and advertisers.
  • Ad is treated as a different digital asset, putting the client under great pressure.
  • Video quality might fluctuate while switching between the actual content and ads.

Related Terms


Codecs help rapidly compress and decompress media files while maintaining the original video's quality—reducing the required bandwidth and allowing multimedia files to be transmitted and accessed easily over networks.

CDN - Content Delivery Network

CDN or Content Delivery Network is a geographically dispersed network of servers and data centers used to quickly and efficiently deliver content.

CBR - Constant Bitrate

CBR or Constant Bitrate is a method used in encoding wherein the video encoder maintains a constant bit rate regardless of the size and complexity of the files being processed.

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