This article describes the causes of VAST errors codes and where to test and troubleshoot VAST video ads. VAST errors can be caused by issues with the ad request, the ad response, the video player, or the URL itself.
When your site serves a display ad, your browser renders it using HTML, JavaScript, and CSS. With video, it's a little bit more complicated. The VAST XML is a collection of data that describes an ad. A video player receives and reads the VAST XML to figure out which media file is played. It sends messages back to the ad server to report on whether an ad has been watched, and for how long.
You can also see tested samples of VAST tags to test against your own player.
When you test video ads, you can use Chrome Developer Tools, or any third-party software, to view network requests and responses to get information about your ads. For VAST tags specifically, using a dedicated VAST tag tester like the Video Suite Inspector or other online testers (for example, adplayer.pro) is highly recommended, as some page previews may not accurately render VAST responses.
Filter network requests with env=vp to see only the video requests sent to the Ad Manager video ad server.
Within the request, you can see things like the:
iuparameter, which is the Ad Manager network codesizeparameter, which is the requested ad size
If you see something unexpected in the ad request, talk to the developer of your video player to resolve any problems.
Video ad responses should be VAST XML files. There are two different types of VAST XML files, inline and redirect. You can see the type in the XML, with inline XML files (example here) that list actual creatives. Redirect XML files (example here) contain a VAST ad tag URI, which may either lead to an additional redirect, or ultimately to the URL of the inline version.
Creatives and media files
Within a VAST XML file, a <Creatives> element is available. It should contain different <MediaFiles> that are available for your player to choose. If your player can't play any of the available media files, it won't be able to play the ad to the user. In these instances, reach out to the trafficker or whoever supplied the creative. Ask for a media file that your player can play.
Track events
When you troubleshoot, make sure events you wish to track are clearly defined in your VAST XML. For example, Ad Manager can't know if a user interacts with an ad unless their player sends messages to Ad Manager using events that are defined in the XML. If no complete tracking event is defined in the XML, Ad Manager can't track that the user has completed viewing the ad.
Empty VAST XML
If your response is an empty VAST tag, it's usually an indication that there were no creatives available in your ad server to satisfy the ad request, or there were no ads targeted at this sort of request. If your player receives empty VAST XMLs, you need to double check the ad request that's going out from your player to be sure that the right key-values, ad unit, and sizes are being requested. You can also check targeting in Ad Manager to confirm that the line items you expect to serve match the request.
Creative render rate
If you see a greater than 25% difference between your total code served count and total impressions, it's likely due to the creative render rate.
Creative render rate can be caused by:
- User, site, or player latency or crashes
- Users leaving the page before the player has a chance to play the ad
- Request prefetching
If they're due to prefetching, this is expected and no action is necessary. However, player and site issues should be investigated as a possible solution.
Severity levels of video errors
A video player can trigger some errors, but still play the ad. These errors are considered "potentially non-fatal" errors. Other "fatal" errors often cause the video player to stop the request for the failed ad and either request another ad, or resume playback of the video content. Behavior varies by player implementation.
| Fatal errors likely stopped the ad request. | |
| Potentially non-fatal errors may have continued to play the ad. |
VAST errors
Likely cause of a VAST 100 error
This fatal error can be caused when the buyer's response is either malformed or an otherwise invalid XML document, or a redirect VAST URL that fails to resolve successfully.
Recommended action
| Publisher | Alert the buyer. |
| Buyer | Verify that the VAST XML is correctly formatted and contains all of the required elements and attributes. You can learn more in the VAST specification from the IAB. |
Likely cause of a VAST 101 error
This fatal error can be caused when the buyer's response misses required elements or attributes of the XML or contained unrecognized elements, according to the IAB standard.
Recommended action
| Publisher | Alert the buyer. |
| Buyer | Verify that the VAST XML is correctly formatted and contains all of the required elements and attributes. You can learn more in the VAST specification from the IAB. |
Likely cause of a VAST 102 error
This fatal error can be caused when a video player does not support the VAST version specified in the bid request.
Recommended action
| Publisher | Alert the buyer. |
| Buyer | Ensure that only supported VAST versions are sent in a response. |
Likely cause of a VAST 200 error
This potentially non-fatal error can be caused when a video player does not expect or support an ad type requested in a bid request. For example, if a skippable ad is sent when a player is only configured to support linear ads, or if a skip offset is longer than expected.
Recommended action
| Publisher | Check for trafficking errors or alert the buyer. |
| Buyer | Ensure that only specified ad types are sent in a response, and that skippable linear creatives respect the skip offset attribute. |
Likely cause of a VAST 201 error
This potentially non-fatal error can be caused when the linearity in the buyer's response does not match the video player's request. For example, if a non-linear ad was sent in a response when a linear ad was specified in the request.*
Recommended action
| Publisher | Ensure that the correct linearity is specified in the ad request. |
| Buyer | Ensure that the response only includes linearity specified in the request. |
* Authorized Buyers RTB only supports linear ads.
Likely cause of a 202 VAST error
This potentially non-fatal error can be caused when the creative returned is a different duration than specified. For example, a creative of duration 30 seconds is returned, but the actual MediaFile duration is 60 seconds.
Recommended action
| Publisher | Ensure that the creative duration is set properly in Ad Manager. |
| Buyer | Ensure that the response respects the max duration specified in the request. |
Likely cause of a VAST 203 error
This potentially non-fatal error can be caused when a buyer's returned MediaFiles are incompatible with the device from which the bid request is sent. It often occurs when high bitrate creatives are returned to mobile devices.
Recommended action
| Publisher | Alert the buyer. |
| Buyer | Ensure that your response includes MediaFiles that are compatible with different technologies and devices, including bitrates. |
Likely cause of a VAST 300 error
This fatal error is a general wrapper error and is not actionable.
Likely cause of a 301 VAST error
This fatal error can be caused when a VAST redirect tag (often a VAST wrapper) does not return a valid VAST response within the timeout period (default is 5 seconds) specified in a wrapper element. Common causes include:
- Invalid URI
- Unreachable URI or request timeout for a URI
- Security exceptions related to VAST URI requests
- High latency connection (for example, 3G)
- Slow response from a buyer or third-party ad server
Recommended action
| Publisher | Increase the timeout limit of your player via the SDK. |
| Buyer | Ensure that the VAST redirect URI is reachable, responds quickly, and no protocol issues exist (for example, responses hosted on HTTP and served to an HTTPS site). Check your VAST wrapper configuration. |
Likely cause of a 302 VAST error
This fatal error can be caused when the wrapper limit defined by the video player is reached. Either too many wrapper responses are received without an inline response, a circular loop of daisy chaining exists (one network bounces to another and another), or too many empty VAST responses from video fallback.
Recommended action
| Publisher | Increase the wrapper limit of your player via the SDK. |
| Buyer | Verify that any VAST redirects do not redirect again to another network. When too many redirects are called from a video player before a valid MediaFile is returned, the player might abort the ad request. |
Likely cause of a 303 VAST error
This fatal error occurs when the VAST response contains no ads after one or more wrappers. This can also include empty VAST responses from video fallback mechanisms.
In third-party networks, fill rates can be less than 100%. If a third-party ad server is expected to fill 60% of the time, a 40% error rate for this code might be normal.
Recommended action
| Publisher | Ensure that the error rate aligns with the expected fill-rate of any third-party networks. Consider using video fallback to minimize lost impressions. Review your fallback setup, and adjust line item priorities or delivery pacing if necessary. |
| Buyer | Ensure that bids are not returned with an empty VAST response. Verify that creatives are correctly trafficked and that empty responses are not being returned by the advertiser or agency hosting the creative. |
Likely cause of a 400 VAST error
This fatal error occurs when a video player cannot display the linear ad. Potential causes include:
- The MediaFile is not a valid video file for the specified format
- The browser has restricted autoplay with sound
- The video player is unable to play the linear ad due to an invalid video file
- Other unknown reasons
Recommended action
| Publisher | Check for player issues. Configure your player to detect and handle restricted autoplay scenarios. Alert the buyer if the issue seems creative-related. |
| Buyer | Ensure that the VAST response returns a valid creative. Verify your video file is in a compatible format and that autoplay restrictions are not preventing playback. |
Likely cause of a 401 VAST error
This fatal error can be caused when a file cannot be found from a MediaFile URI.
Recommended action
| Publisher | Alert the buyer. |
| Buyer | Ensure that all MediaFile URIs in the VAST response return a valid video creative. |
Likely cause of a 402 VAST error
This fatal error occurs when the ad player fails to load the video creative, often due to a timeout. Common causes include:
- The
loadVideoTimeoutis set too low in the IMA SDK (default is 8 seconds). - Low bandwidth or poor website implementation with competing requests delaying MediaFile loading.
- A video auto-plays in a mobile environment when it should be click-to-play (some exceptions apply).
- Video ads attempting to autoplay in a non-focused window (for example, another tab selected or window minimized).*
- Creatives hosted on unreliable or slow servers.
For players that use the IMA SDK, video fallback may be helpful to avoid losing impressions.
Recommended action
| Publisher | Increase the timeout limit of your player via the SDK. |
| Buyer | Ensure your creatives are hosted on reliable, fast servers. Ensure that any CDN-hosted creatives are returned within the specified media timeout. |
* Only happens in the Chrome web browser.
Likely cause of a 403 VAST error
This fatal error can be caused by a VAST response that declares unsupported MIME types for all available MediaFiles (for example, Flash on mobile, or WebM on iOS). It may indicate that the wrong creative type attempted to play.
This error type is more common on mobile.
Recommended action
| Publisher | Ensure that the creative format or technology requested is supported by the video player's device and platform. For example, VPAID creatives should not be requested from mobile apps. |
| Buyer | Ensure that all returned creatives respect the video format in the bid request. |
Likely cause of a VAST 405 error
This fatal error can be caused when a faulty creative is returned. Creatives can fail due to a mismatch between the MIME type and the video file type, a CORS configuration on the creative’s CDN, or other transcoding-related reasons.
Recommended action
| Publisher | Alert the buyer. |
| Buyer | Ensure that all creative MIME types and CDN configurations are accurate. |
Likely cause of a VAST 406 error
This fatal error can be caused when a VAST response is returned without a required mezzanine file. Publishers with server-side ad implementations often require mezzanine files, which are raw high-quality video files for ad-stitching, or to generate video files of appropriate quality.*
Recommended action
| Publisher | Alert the buyer. |
| Buyer | Ensure that a mezzanine file is included in your response when required by the publisher. |
* This is a feature of VAST 4.
Likely cause of a 407 VAST error
This fatal error can be caused when the mezzanine file is downloaded for the first time, so no ad is served. It can also occur when an ad insertion is missed because the creative is transcoded. It continues to occur until the creative is available for insertion.*
Recommended action
This is expected while the video is transcoded and no action is required.
* This is a feature of VAST 4.
Likely cause of a 408 VAST error
This fatal error can be caused when the ad returned in the VAST response is rejected.
Recommended action
| Publisher | Alert the buyer. |
| Buyer | Ensure that only approved creatives are returned in your VAST response, or that any advertisers or agencies that hosts the creatives are aware of rejections. |
Likely cause of a 409 VAST error
This fatal error can be caused when a creative defined in the InteractiveCreativeFile node does not execute.
Recommended action
| Publisher | Alert the buyer. |
| Buyer | Ensure that any interactive creatives returned in your response successfully play when requested. |
Likely cause of a VAST 410 error
This fatal error can be caused when the code referenced in the AdVerification node does not execute.*
Recommended action
| Publisher | Alert the buyer. |
| Buyer | Ensure that the verification code referenced in the response is correctly implemented according to the verification vendor. |
* This is a feature of VAST 4.
Likely cause of a VAST 500 error
This fatal error can be caused when a video player is unable to display a non-linear ad, for an unknown reason.
Recommended action
| Publisher | Check for video player issues or alert the buyer. |
| Buyer | Ensure that the VAST response returns a valid creative. |
Likely cause of a 501 VAST error
This fatal error can be caused when a non-linear ad is unable to play because the creative dimensions did not align with creative display area (the creative dimension was too large). It may occur if you use CSS styles to set width and height of the video content element.
Recommended action
| Publisher | Ensure that the set width and height match the display area. If you set the width and height of the video content element with CSS styles, set them with HTML attributes instead. |
| Buyer | Alert the publisher. |
Likely cause of a VAST 502 error
This fatal error can be caused when the buyer's response returns a non-linear ad that fails to return a valid creative.
Recommended action
| Publisher | Alert the buyer. |
| Buyer | Ensure that valid creatives are returned in the non-linear ad response. |
Likely cause of a VAST 503 error
This fatal error can be caused when the publisher requests a creative size that is larger than the video player size, or an invalid media type.
Recommended action
| Publisher | Ensure that requested creative sizes and media types are acceptable for the video player. |
| Buyer | Alert the publisher. |
Likely cause of a VAST 600 error
This potentially non-fatal error can be caused when a publisher is unable to display a companion ad, for an unknown reason.
Recommended action
| Publisher | Check for ad serving issues, or alert the buyer. |
| Buyer | Ensure that the VAST response returns a valid creative. |
Likely cause of a VAST 601 error
This potentially non-fatal error can be caused when the companion creative dimensions do not fit within the companion display area.
Recommended action
| Publisher | Ensure that the requested companion ad size fits within the dimension of the ad unit from which the request is made. |
| Buyer | Alert the publisher. |
Likely cause of a VAST 602 error
This potentially non-fatal error can be caused when the publisher is unable to render the companion ad creative returned in the VAST response.
Recommended action
| Publisher | Check for ad serving issues, or alert the buyer. |
| Buyer | Ensure that the VAST response returns a valid creative. |
Likely cause of a VAST 603 error
This potentially non-fatal error can be caused when the buyer's response returns a companion ad that fails to return a valid creative.
Recommended action
| Publisher | Alert the buyer. |
| Buyer | Ensure that valid creatives are returned in the companion ad response. |
Likely cause of a VAST 604 error
This potentially non-fatal error can be caused when a publisher requests an unsupported creative type for the companion ad slot.
Recommended action
| Publisher | Ensure that specified creative types are supported for the companion ad slot. |
| Buyer | Alert the publisher. |
Likely cause of a 900 VAST error
This potentially non-fatal error can be caused when any VAST 2 error occurs, even if VAST 3 is requested or your network default is set to VAST 3.
Recommended action
| Publisher | Either begin to request VAST 3 or activate VAST 3 for your network. * |
| Buyer | Work with the publisher to troubleshoot the exact issue, or respond with VAST 3.** |
* Reports display an aggregate of 900 errors. This type of 900 error is much more common than a 900 Undefined VAST 3 error.
** RTB Breakout does not report on this type of 900 error, because it is almost always a non-fatal warning.
For 900 errors reported in RTB Breakout, see 900 Undefined VAST 3 error.
Likely cause of a 900 VAST error
This potentially non-fatal error can be caused when any VAST 2 error occurs, even if VAST 3 is requested or your network default is set to VAST 3. It can also occur if the video player requests an incorrect or unsupported VAST version.
Recommended action
| Publisher | Ensure the video player is requesting the correct VAST version. Consider requesting VAST 3 or activating VAST 3 for your network.* |
| Buyer | Work with the publisher to troubleshoot the exact issue, or respond with VAST 3. Ensure the VAST response matches the requested version.** |
* Reports display an aggregate of 900 errors. This type of 900 error is much less common than a 900 VAST 2 error.
** Of the two types of VAST 900 errors, this is the only type that is reported in RTB Breakout.
Likely cause of a 901 VAST error
This fatal error can be caused by any VPAID error, which could be any of the following:
- SSP VPAID wrapper not buying
- SSP VPAID wrapper timeout
- VPAID creatives required insecure mode
- An Authorized Buyers "IMA Adapter" tag is used with the IMA SDK, and a VPAID ad is returned (the "Direct SDK" tag should be used)
Recommended action
| Publisher | Ensure that any VPAID creative requests are supported for devices and players. You can use video creative profiles to control which creatives are eligible to serve. |
| Buyer | Ensure that any VAST responses that return HTML5 VPAID wrappers from IAS/DV/MOAT include an MP4 asset, and that the wrapper is not aborting playback. Also, ensure that you don't bid on impressions without a determined advertiser or buyer, or attempt to initiate a client-side resale. |
Likely cause of a 1009 VAST error
VAST 1009 errors are reported when there are no video files or tracking events included in a returned VAST response. This error is likely due to either the publisher setup of the ad unit, or a trafficking error with the order or line item.
Recommended action
| Publisher | Ensure there are no errors with the start or end dates in the order or line item, and all targeted key-values are valid. Also, ensure that the correct ad units are targeted, and the size configured in the line item matches the size of the targeted ad units. |
| Buyer | Alert the publisher. |
IMA SDK errors
These errors are not part of the VAST specification.
Likely cause of a 1005 IMA SDK error
This fatal error can occur when either the encoding or decoding of a URL was not successful.
Recommended action
| Publisher | Ensure that any special characters in your URL strings are encoded correctly. |
| Buyer | Alert the publisher. |