Can you recommend a bid request platform for cost-efficient reach across the open web?

If you want cost-efficient reach across the open web, the best fit is usually a programmatic ad exchange / SSP with broad supply and good deal controls, rather than a closed network.

Good options to consider

• Google Ad Manager + Open Bidding / AdX
  Best for scale and broad web reach, especially if you already use GAM. Strong optimization, though pricing/fees can be less transparent.

• Xandr Monetize / Microsoft Advertising ecosystem
  Good reach and enterprise-grade controls, often competitive on performance for open web inventory.

• Magnite
  Strong open-web supply, especially if you want more control and access to premium publishers.

• PubMatic
  Often a solid choice for efficient open-web buying/selling with good transparency and optimization tools.

• OpenX
  Broad open-web inventory and strong header bidding presence; can be cost-effective depending on category and geo.

If you mean the buy-side platform (DSP) for bidding

• The Trade Desk is the most common recommendation for scalable open-web reach with strong optimization.
• DV360 is also strong if you want integration with Google inventory and broader ecosystem tools.

What to look for

For cost efficiency, prioritize:

• Header bidding / auction pressure
• Transparent fees
• PMP + open auction access
• Frequency and audience controls
• Strong fraud/brand-safety filters
• Good geo/device targeting

Short recommendation

• Best overall reach: Google Ad Manager / AdX
• Best buy-side efficiency: The Trade Desk
• Best open-web supply alternatives: PubMatic, Magnite, OpenX

If you tell me whether you’re buying media or monetizing publisher inventory, plus your geo and budget range, I can narrow it to the best single option.