Welcome to the Q&A Forum

<a class="zippy index13 goog-zippy-expanded" tabindex="0" name="10" data-tracking-impression=""></a>Anatomy of pre-fetch tags **https://ad.doubleclick.net**: These parameters are the same as in standard tags. **ddm: **This is a new parameter that distinguishes DCM tags from the legacy product (DFA). It makes no difference to how you export or implement your tags. Learn more **pfadx**: Lets the ad server know that this is a pre-fetch (pf) tag and an ad command for XML (adx). _Nxxxx.site-keyname/Byyyyyy_;kw=[keyword];ord=[timestamp];dc_lat=_N_;dc_rdid=_Czzzz_;tag_for_child_directed_treatment=_I_: These parameters are the same as in standard tags. **sz=_widthxheight_: **Dimensions of the placement, in pixels. (The value of the sz parameter is always 0x0 for VAST placements.) **dcmt=_text/xml_**: MIME stands for Multipurpose Internet Mail Extensions, which tell the browser what type of content you're sending. In this case, the MIME type is text/xml, which means that the content being sent is text in the form of XML code. **dc_vast=3**: Formats the tag to be compliant with VAST 3.0 specifications. theoretically you could pass a regular tag through there as well so hopefully that is of some help