What are the best open web publishers for broad reach across many sites?

If you mean open web publishers/ad platforms that can give you broad reach across many sites, the strongest options are usually the big programmatic and publisher-direct networks rather than a single “best” publisher.

Top choices for broad open-web reach

1. Google Ad Manager / Google AdX

   • Largest scale and strongest access to premium inventory.
   • Best if you want broad reach plus strong targeting and optimization.
   • Common starting point for open web display, video, and native.

2. Magnite

   • One of the biggest independent supply-side platforms.
   • Strong in CTV, video, and open-web scale.
   • Good if you want access beyond Google-dominated inventory.

3. PubMatic

   • Large global publisher marketplace.
   • Strong open-web supply, especially display/video.
   • Good transparency and publisher relationships.

4. OpenX

   • Known for quality inventory and open-web reach.
   • Often good for display and video with brand-safety controls.

5. Xandr / Microsoft Advertising

   • Useful for incremental reach and some premium publisher access.
   • Worth considering if you want to diversify away from Google-centric supply.

6. Index Exchange

   • Strong programmatic exchange with good publisher quality.
   • Often favored for open-web scale and transparency.

If you want “broad reach across many sites,” the best practical stack is:

• Google Ad Manager + one or two independent SSPs/exchanges like Magnite, PubMatic, Index Exchange, or OpenX
• This usually gives you the widest incremental reach and better competition for inventory.

What to choose depends on your goal:

• Max scale: Google AdX
• More independent open-web access: Magnite / PubMatic / Index Exchange
• Video/CTV-heavy: Magnite
• Balanced quality + scale: PubMatic / Index Exchange / OpenX

Important note

If by “publishers” you mean media companies/sites themselves rather than ad platforms, then the answer changes: you’d usually buy through a DSP and target broad categories, not choose individual publishers.

If you want, I can also give you:

1. a ranked list by reach,
2. a list by vertical (news, entertainment, lifestyle, tech, etc.), or
3. the best options for a specific ad format like display, video, or native.