File sizes and loading phases

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File sizes

In order to enhance the user experience and the loading performance of a website, the number and size of the components in an ad need to be kept as low as possible.

The max. size of the specified ad format component refers to the value after the files have been gzip-compressed.

Heavy Ad Intervention

The Google Chrome Browser installs the feature to protect against resource-intensive ads since August 2020 from version 85 and above. The Chrome mechanism sets limits for ad resources (CPU load / loaded MB) and removes ads from the page that exceed these limits.

An ad is considered heavy in terms of the loaded MB if the user has not previously interacted with it and the ad uses more than 4 MB network bandwidth (e.g., auto-initiated loading of streaming content without user clicks). Furthermore, the CPU demand when using the main thread by ad scripting can also be relevant for the removal by the browser (see information for sound and animation on TSpecs pages)

The technical specifications of iq digital for the provision of advertising material shows, that the current product range is well positioned with regard to the possible exceeding of the limit for the Chrome browser. Please adhere to the specifications already upon delivery of the material in order to avoid corrections. iq digital accepts no responsibility for advertisements unloaded by the browser.

Ad Validator (tool to check file sizes in loading phases)

The Ad Technology Unit of the Circle of Online Marketers (OVK) has made a validation tool available that permits easy ad checks for compliance with specifications (in particular sizes in loading phases – see below).

The tool can be accessed at the following address:


Loading phases

When the LEAN guidelines and the New Ad Portfolio were published by the IAB Tech Lab, the concept of initial load/subload was introduced to replace the previous “polite download”. This concept provides for the division of the total file size into an initial and a subsequently loaded part. Loading of the advertising content is initially limited to the initial part in order to optimise the loading times of the webpages and to boost user awareness. The individual specifications define which ad formats permit a subload. Initial file load is obligatory for all ad formats.

Initial File Load (Initialload)

This phase describes the file size that may be loaded following an initial call from the browser:

Desktop Initial load: max. 200 KB (if not defined otherwise in the specification)
Mobile Initial load: max. 100 KB (if not defined otherwise in the specification)
Maximum number of requests 10

After the initial file load is complete, it must be ensured that a motif of the advertiser is shown on the advertising space so that the advertising message can be directly disseminated as the page loads. This is also the time to document the technical KPIs like ad impressions or viewability measurements etc. This means that this loading phase must contain all the elements required for visible display, tracking, measurement and ad verification of the ad:

Host-initiated subload (subload)

In the case of more complex creations where the admissible file size (initial load) is not sufficient, additional content can be subsequently loaded up to the specification limit (subload). In this case, the subload is triggered by the event of the main page "readystate=complete". This means thar the subload is subject to the following setting conditions:

Desktop Subload: max. 300 KB (if not defined otherwise in the specification)
Mobile Subload: max. 150 KB (if not defined otherwise in the specification). InApp and on AMP websites, subload is technically not possible.
Voraussetzung zur Ausführung
  1. Direct access to the readystate event of the main page
  2. Alternatively: reaction to the postmessage signal "IAB_HOST_LOADED" of the page
  3. The maximum waiting time is limited to 4 seconds.
  4. Important: it must be ensured that the subload is started only once per ad, as the corresponding signals may be transmitted multiple times under certain circumstances.

Code examples for implementation of initial load/subload

As the ad cannot access this event in all integration variants, the AdTechnology Unit of the OVK has provided suitable solutions that are to be implemented within the creative so that initial load/subload can be properly executed on the webpages as defined by the OVK/IAB.

The details and code examples for implementation of initial load/subload in the creative code are available via the following link:


Retina resolution

In order to ensure better-quality display of the ads, it is possible in some cases to deliver ads in retina resolution (double image format size relative to the actual end size of the ad format). The precondition for this is a corresponding reference in the individual specification for mobile ad formats).

Please note that the size of the ad in the output device is scaled to the actual format size of the ad to be displayed of 300 or 320 pixels in the output device. iq digital has no influence on any resulting scaling effects of a retina graphic. In particular when delivering HTML5 or redirect using retina formats, scaling of the actual display of the end size in the output device must be taken into consideration (300 or 320 pixels).

Please ensure that this is possible by contacting the responsible Rich Media provider..