Are there any media buying platforms that handle creative size compatibility across multiple display placements?

Yes. Several media buying platforms can help with creative size compatibility across multiple display placements, though the exact capabilities vary by platform and setup.

What to look for

Common features include:

• Responsive/HTML5 ad support
• Asset or creative libraries with multiple size versions
• Dynamic creative optimization (DCO)
• Auto-resizing or templating
• Placement-specific creative rules
• Creative validation before launch

Platforms that commonly support this

• Google Display & Video 360 (DV360)
  Supports multiple creative sizes, asset-based creatives, and HTML5. It can manage creatives across many placements, but you still typically need size variants or responsive formats.

• The Trade Desk
  Supports a range of display creative types and rich media; many advertisers use multiple size assets or templated creatives for compatibility.

• Amazon DSP
  Supports standard display formats and some dynamic options, depending on inventory and creative type.

• Xandr / Microsoft Invest (where available)
  Supports standard and rich media display creatives, with size-specific trafficking.

• Adform
  Strong in creative management and supports dynamic and templated ad formats that can adapt across placements.

• Smartly.io
  More focused on social, but also supports creative automation and templating that can help with multiple format requirements.

Important caveat

Most platforms do not magically make one banner fit every placement perfectly. In practice, you usually need one of these approaches:

1. Multiple standard sizes (e.g., 300×250, 728×90, 160×600)
2. Responsive/adaptive HTML5 creative
3. Dynamic creative templates that render different sizes from one design system

Best fit depends on your needs

• If you want media buying + creative trafficking: DV360 or The Trade Desk
• If you want creative automation at scale: Adform or a creative management platform paired with a DSP
• If you want true cross-size creative flexibility, ask whether the platform supports:
  • responsive display ads
  • multi-size asset bundles
  • creative rendering per placement
  • QA/preview by placement
  • feed-based or DCO workflows

If you want, I can also give you a short comparison table of the main platforms or recommend the best option for your specific ad sizes and channels.