Rich Media creatives

Collect site specs

The media agency is responsible for collecting site specs. It's best to start this process when the media agency begins the request for proposal (RFP) for the site or purchases the media.

Different publishers often have different specifications for Rich Media creatives. So to make sure your ad can run across all sites, create a lowest common denominator (LCD) chart (see below) and deliver it to your creative agency before the unit is built. If you build to the LCD, we’ll be able to build one ad that conforms to the limits of multiple sites.  

If you haven't finalized creative specs yet but want to provide guidelines to the creative team, show them Best practices for LCD guidelines in the interim.

Spec collection is a three-step process:

Step 1: Finalize the media plan

The media plan document must include:

  • A list of the sites targeted for your campaign, with start and end dates, impression levels, and placement names if available
  • Creative ad sizes (e.g. 300x250, 728x90) and types (e.g. expanding, floating) for each site
  • Features for each type (video, audio, etc.)
  • Names, email addresses, and phone numbers for your trafficking and sales contacts for each site

Step 2: Collect site specs from each site

These must include the sizes and types of units that you're running in the media plan. Use these forms:

Step 3: Generate an LCD

After site specs are gathered, generate an LCD. The LCD is based on the smallest file size, expansion size, expansion direction, etc. for each size and type of banner chosen to accommodate all publishers on the media plan. Please fill out the first tab of this spec sheet.

To find an LCD, look at all the ad specs for the publisher sites you want to serve on. Then take the smallest file size, expansion size, expansion direction, etc. for each size and type of creative.


Let's say your client wants to run an expanding ad on three sites. Here are examples of some specs for each:

Site Size Expand direction Expand size Initial load Subsequent (polite) load Total load Expansion method
Site 1 728 x 90 left 728 x 240 40 K 70 K 110 K Click to expand
Site 2 728 x 90 left 728 x 260 35 K 55 K 90 K Mouse-over or click to expand
Site 3 728 x 90 right 728 x 120 40 K 60 K 100 K Mouse-over or click to expand

What's the LCD?

Site Size Expand direction Expand size Initial load Polite load Total load Allowed expand directions
LCD 728 x 90 MDE 728 x 120 30 K 55 K 90 K Click to expand.1

1If one site requires mouse-over and another requires click to expand, you must create two units, one for each requirement.

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