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According to statistics compiled by Cisco Systems, over 80% of all published content on the internet is video traffic. Consequently, video ads are one of the most critical forms of online advertising today

Most video ads on the internet must adhere to the specifications outlined by the Video Ad Serving Template (VAST) standard to ensure functionality and compatibility with video players. One of the most common issues encountered by publishers producing video advertising through Google platforms, such as YouTube and Google AdSense, is VAST error codes. 

Learn what VAST error codes are, which error codes are the most common, and how to resolve them.

What is a VAST Error?

A Video Ad Serving Template error code is one of the many possible error states defined by the Interactive Advertising Bureau (IAB). A VAST error indicates an issue between the server hosting the ad content and the target consumer’s video player, which may hinder or prevent the proper displaying of the ad

The exact nature of the error depends on the code displayed; each code corresponds to an identified issue.

Common Challenges for Displaying VAST Ads in Ad Tech

Although displaying VAST ads tends to be simpler to implement and more cost-effective in the long run than alternative solutions like Video Player-Ad Interface Definition (VPAID), the primary challenge for publishers is ensuring ad viewability

Many types of technical issues frequently disrupt the viewability and functionality of VAST ads. In many cases, disruptions occur due to improper configuration settings, either on the buyer’s or publisher’s end. These disruptions manifest in the form of VAST error codes.

VAST error codes are categorized into two severity levels: fatal errors and potentially non-fatal

Common VAST Fatal Error Codes and How to Resolve Them

A fatal VAST error code is the most severe because it is the most likely to have stopped the ad request, resulting in a display disruption. Some common VAST fatal errors include:

VAST Error 100: XML Parsing Error

VAST Error 100 is one of the most common fatal errors. Potential causes behind VAST Error 100 include a malformed buyer response or an invalid, corrupted, or improperly formatted XML document. Another possibility is a VAST URL redirect issue, for example, when the redirect does not resolve correctly.

Publishers noticing an Error Code 100 should alert the buyer. In turn, buyers must verify that the VAST URL is properly configured, then ensure that all VAST XML documents are functional and correctly formatted with the proper attributes. 

VAST Error 101: Schema Validation Error

A schema validation error typically occurs when the buyer’s response is missing the required XML elements or attributes or contains unrecognized elements.

The best way to address an Error 101 code is for the buyer to consult IAB documentation, check VAST XML specifications, and ensure all required and correctly formatted elements are present.

VAST Error 102: Response Version Not Supported

This commonly-occurring error code is triggered when a target video player does not support the bid request’s VAST version. This may also happen if the exchange sent the wrong VAST version.

In rare instances, the VAST ad may not specify a version number. In that case, it can also be considered a schema validation error.

To remediate Error 102, the buyer must ensure that responses only feature supported VAST versions.

VAST Error 300: Wrapper Error

VAST Error 300 is a general wrapper error. It is triggered when the wrapper limit is reached.

This error code is non-actionable; there are no resolution methods. However, there are a few remedial steps that can potentially prevent an Error 300 from displaying, such as periodically reviewing VAST URIs and ensuring none of them are timing out.

VAST Error 301: Redirect Timeout Reached

The IAB initially defined Error Code 301 to indicate a faulty, non-responding, or timed-out VAST URI. However, ad tech specialists typically associate Error 301s with high latency (colloquially known as “lag”) and poor or unstable internet connections.

Potential direct causes of an Error 301 include:

  • The player timeout setting is too low (the default setting is 5)
  • Wrong creative dimension (ad size)
  • Invalid URI
  • Timeout of VAST URI
  • High latency
  • HTTP to HTTPS
  • Poorly optimized website

VAST Error 302: Wrapper Limit Reached

The video player receiving an ad is typically configured with its own predefined wrapper limit. Reaching this limit is the most common cause of an Error 302 code.

Error 302s usually occur due to an excessive number of wrapper responses received without an inline response. The remedial action is for the publisher to increase the video player’s wrapper limit.

In rare instances, Error 302s happen due to daisy-chaining: a looping or an excessive number of VAST redirects before returning a media file, causing the video player to abort the ad request. In that instance, the buyer must ensure that no VAST redirects point to another redirect.

VAST Error 303: Empty VAST Response Returned

Error Code 303 indicates an empty VAST response, typically due to an ad request contained inside a third-party wrapper

Buyers and publishers working with third-party networks must check the fill rate, which is usually under 100%. For instance, a fill rate of 86% means there is a 14% chance of this error occurring.

To resolve a VAST Error 303, publishers should enable the fallback feature in Google Ad Manager. Follow these steps:

  • Log into your Google Ad Manager account and open the dashboard.
  • Click the Admin button on the left-hand panel, navigate to Video, then Video Settings.
  • Enable Video Fallback, then click on Save.

VAST Error 400: General Linear Error

A VAST Error 404 is usually the result of a video player being unable to display a linear ad

The most common causes of a failure to display linear ads include:

  • The web browser restricts automatic playing (autoplay) with sound
  • The MediaFile format is invalid (e.g., not a valid video file or incorrectly specified format)
  • Unknown or unspecified source

Publishers noticing an Error 400 should check for video player issues and configure the player to detect browsers with restricted autoplay. If these measures do not remedy the problem, buyers should check the VAST response and ensure it returns a valid creative.

VAST Error 401: MediaFile Not Found

If you see an Error Code 401, it indicates the MediaFile URI does not return a valid video creative or cannot otherwise find a valid video file. 

Publishers finding this error code should alert buyers as soon as possible, and buyers must ensure all of their MediaFile URIs return a valid video creative.

VAST Error 402: Unable to Download or Timeout of MediaFile URI

A VAST Error 402 can have multiple possible causes. The following four issues are the most likely:

  • The value (in milliseconds) at the loadVideoTimeout variable in the file’s IMA SDK is too low. If the page load time takes longer than this value, ad playback will be canceled, potentially resulting in an error.
  • Poor website performance or optimization, causing sufficient load time delays to cancel ad playback
  • The video file auto-plays or attempted auto-playing in a mobile environment where it isn’t intended to behave this way (most video ads on mobile should be click-to-play except in select instances)
  • On Google Chrome browsers, showing a video ad in an autoplay environment despite the window not being in focus (e.g., minimized window, different tab selected, or another program on another screen currently active)

Although not all of these causes have corresponding remedies, the recommended solution for publishers is to inspect the video player’s timeout limit and set the loadVideoTimeout variable to a higher value. The default value is -1, corresponding to 8 seconds (8,000 ms). 

Other potential solutions include website optimization to achieve faster load speeds or adjusting the video bitrate for better ad serving performance on mobile devices.

VAST Error 403: Response Declared Unsupported MIME Types for All MediaFiles

This error code is among the most frequently encountered and is most common on mobile devices. 

Error Code 403 indicates a VAST response has declared one or multiple unsupported Multipurpose Internet Mail Extensions (MIME) types for all available MediaFiles (e.g., attempting to play Flash content on mobile). This error code may also occur when the wrong creative type has tried playing.

When experiencing this error code, publishers must ensure that the ads’ file format and technology are supported by the player’s device and operating system. Buyers must also verify that all returned creatives respect the bid request’s video formats (e.g., mobile apps shouldn’t request VPAID creatives).

VAST Error 405: MediaFile Display Error

A MediaFile Display Error (VAST 405) usually occurs due to a faulty creative. Common failure types include:

  • MIME type and video file type do not match
  • Improper Cross-Origin Resource Sharing (CORS) configuration on the creative CDN
  • Transcoding issue

To address this issue, buyers must verify that all creative MIME types and CDN configuration options are accurate.

VAST Error 406: Missing required mezzanine file

The most common cause of an Error 406 code is a VAST response returned without a required mezzanine file. A mezzanine file is a high-quality, high-resolution video file, often raw (uncompressed) or compressed so that it is indistinguishable from the raw file.

Mezzanine files are typically required in environments relying on server-side ad implementations. These files are employed to generate video files of appropriate quality for the target platform, like for mobile environments or to perform ad-stitching.

Buyers seeing an Error Code 406 must ensure that an appropriate mezzanine file is included in the VAST response.

VAST Error 407: Mezzanine File Downloaded For The First Time

Error code 407 indicates the mezzanine file is being downloaded and transcoded for the first time, causing a failure to serve an ad. This error code is expected and non-actionable; the only remedial action is to wait for the transcoding process to complete.

Depending on the size of the mezzanine file, this process may take several hours.

VAST Error 408: Rejected Ad in VAST Response

If you see VAST Error code 408, it indicates the ad file returned in the VAST response has been rejected.

Publishers should alert buyers of Error 408s as soon as possible, and buyers must ensure VAST responses only contain approved creatives. Entities acting as ad creative hosts (e.g., the advertising or publishing agency) should also be aware of any ad rejections to take appropriate action.

VAST Error 409: Interactive Creative Defined in the InteractiveCreativeFile Node Did Not Execute

The most likely cause of a VAST Error 409 is a failure to play the creative defined by the video ad’s InteractiveCreativeFile node. Buyers must ensure that any interactive creatives (e.g., a playable demo for a mobile game) returned in the VAST response play correctly when requested.

VAST Error 410: Code Referenced In The Verification Node Did Not Execute

VAST Error 410s typically occur due to a failure to execute the code defined in the AdVerification node, a VAST 4 feature. Buyers should ensure that the AdVerification code is functional and correctly implemented.

VAST Error 500: General NonLinearAds Error

If this error code is returned, it typically indicates that the video player failed to display a nonlinear ad for unknown reasons.

Publishers may attempt remediating the error code by checking for video player issues, and buyers should check all VAST responses to ensure they return valid creatives.

VAST Error 501: Nonlinear Ad Creative Dimensions Do Not Align With Creative Display Area

A VAST 501 error is usually the result of a failure to play a nonlinear ad due to a mismatch between the creative dimensions (ad size) and creative display area (screen space). Specifically, Error 501s occur when the creative dimensions are too large for the display area (in other words, the ad is too big for the screen).

In rarer instances, an error 501 can be triggered by incorrectly configured CSS, such as CSS styles fixing the height and width of the video content element.

Publishers can remedy this error code by changing the creative’s set height and width to match the display area. If the publisher has set the video content element’s size using CSS styles, the recommended action is to use HTML attributes instead.

VAST Error 502: Unable To Fetch NonLinearAds/NonLinear Resource

The most common cause of a VAST 502 code is a buyer’s response returning a nonlinear ad that failed to return a valid creative. Buyers must ensure that all nonlinear ad responses return valid creatives.

VAST Error 503: Could Not Find NonLinear Resource With Supported Type

Publishers requesting a creative size larger than the video player’s dimensions may encounter an Error Code 503. An invalid media type may result in this error code in rarer instances.

The recommended remedial action is for the publisher to ensure that all requested creative sizes and media types are compatible with the video player.

VAST Error 901: General VPAID Error

An Error 901 is a generic fatal error code that any VPAID error can cause. Possible causes include:

  • SSP VPAID wrapper has timed out
  • SSP VPAID wrapper not buying
  • VPAID creatives required insecure mode
  • Usage of an “IMA Adapter” tag with the IMA SDK (the correct VAST tag to use is “Direct SDK”)

Publishers must ensure all VPAID requests are supported for target devices and video players. Google’s video creative profile feature can help you manage your creatives and avoid this error code.

Buyers can examine VAST responses returning HTML5 VPAID wrappers and ensure that they include an MP4 asset and do not abort playback.

Common Potentially Non-Fatal VAST Error Codes and How to Resolve Them

A non-fatal error indicates an issue that may not have stopped the ad from displaying. However, addressing the cause of the error as soon as possible is critical to ensure optimal performance and prevent more severe errors. Here are some common non-fatal VAST errors:

VAST Error 200: Video Player Expected Different Ad Type

A VAST Error 200 usually occurs when the video player does not support or expect the ad type requested in a bid request. 

An example of an unsupported ad type is skippable ads sent to players that can only support linear ads.

Publishers can address this error code by checking for trafficking errors. If the publisher can’t solve the issue, the buyer must ensure that VAST responses only send specified ad types.

VAST Error 201: Video Player Expected Different Linearity

This error code is typically caused by a linearity mismatch between the video player’s request and the buyer’s response. An example of a linearity mismatch is a VAST response sending a nonlinear ad when the request specified a linear ad.

Publishers should ensure ad requests specify the correct linearity, and buyers should verify that VAST responses only include the linearity specified in the ad request.

VAST Error 202: Video Player Expected Different Duration

VAST Error code 202 occurs when the response returns a creative with a different duration than specified. For example, if the specified duration is 30 seconds, but the MediaFile’s actual duration is 45 seconds, it may result in an Error 202.

Publishers must properly configure creative duration in Google Ad Manager, and buyers must ensure the response respects the request’s specified maximum duration.

VAST Error 203: Video Player Expected Different Size

This error code is most commonly caused by an incompatibility between the returned MediaFiles and the target device. For example, sending a creative with a high bitrate to mobile devices, even though these devices are better suited for lower bitrates.

Buyers can remedy an Error 203 by ensuring all VAST responses include MediaFiles compatible with multiple types of devices and technologies, including bitrate compatibility.

VAST Error 600: General CompanionAds Error

Error 600 is a generic non-fatal error typically caused by an unspecified issue with companion ads. It most commonly occurs when the publisher cannot display a companion ad for no specified reason.

To address this error code, publishers may try checking for potential ad serving issues, and buyers should ensure VAST responses return valid creative files.

VAST Error 601: Companion Creative Dimensions Did Not Align With Companion Display Area

This error code usually occurs when a companion creative’s size is too large to fit in the companion ad display area.

Publishers should ensure the requested companion ad’s size (height and length) fits within the ad unit’s dimensions. 

VAST Error 602: Unable To Display Required Companion

A VAST Error 602 means the publisher has failed to render the companion creative returned in the corresponding VAST response

This error code is typically the symptom of an ad serving issue, which publishers must check for and address. Buyers should also ensure the VAST response returns a valid creative.

VAST Error 603: Unable to Fetch CompanionAds/Companion Resource

Vast Error 603s usually occur when the buyer’s response returns a companion that could not return a valid creative. The buyer must check and ensure all companion ad responses return valid creatives.

VAST Error 604: Could Not Find Companion Resource With Supported Type

A Vast Error 604 is typically the result of a publisher requesting an unsupported creative type for a companion ad slot.

To resolve this error code, publishers must ensure the companion ad slot supports the specified creative types.

Both Potentially Fatal and Non-Fatal VAST Error Codes

These error codes may or may not correspond to fatal errors.

VAST Error 900: VAST 2 Error (Potentially Non-Fatal)

This specific error code is caused by a VAST 2 error of any type, even if later VAST versions are requested (e..g, VAST 3) or your network default version is VAST 3 or later.

To address this error code, publishers should either start requesting VAST 3 or activate VAST 3 on their network. Buyers are advised to work with the publisher for more specific troubleshooting.

VAST Fatal Error 900: Undefined VAST 3 Error

This error code is returned when an unknown VAST 3 error has occurred and stopped the ad request. Due to the non-specific nature of this error code, publishers and buyers are advised to work together to identify the exact issue.

Best Practices for the Publishers to Handle Errors

Although the best way to avoid error codes of any type is to prevent the conditions necessary for an error code to occur, they are sometimes unavoidable. Here are a few best practices for publishers to follow:

  • Pay close attention to the error code number. Many errors can be resolved or mitigated without contacting the buyer, saving a significant amount of time.
  • Ensure that Demand Side Platforms (DSPs) have the opportunity to scan every creative and resolve potential error-causing issues before serving the ad.
  • Communicate and partner with your DSPs, Supply-Side Platforms (SSPs), ad networks, and ad servers to improve the performance of your creatives.

Resolve the VAST Error Codes with CodeFuel

Understanding the nature of each VAST error is critical to addressing all potential ad serving problems and optimizing your video advertisements’ performance.

If you need assistance resolving VAST errors, CodeFuel can help. Our team of video ad experts and monetization specialists can assist and resolve any VAST error codes that may occur. Contact us today for more information.