For publishers, 100% viewability is not a future theoretical but a present reality.

Viewability demands on three advertiser requests for proposals obtained by Ad Age show the standard is now a common requirement sent to publishers.

"As part of this media buy, we will be requiring a quality guarantee of 100%," reads one RFP. "This means 100% of the media must be viewable, bot-free, and served within appropriate content."

Another gets more specific, telling publishers that ad-quality monitor Integral Ad Science will be watching performance, and only ads meeting the MRC viewability standard (at least 50% of the ad viewable for one second) will be billable. "We will seek make-goods for all impressions out of view."

The third is slightly softer but still clear in its demand: "Publishers who are able to guarantee viewability through this service will be prioritized."

The Interactive Advertising Bureau recently asked for patience from advertisers demanding 100% viewability, saying 70% is more realistic due to technical hurdles. But advertisers don't seem to be willing to play along.

These requirements were far less present a year ago, said one publishing executive who asked to remain anonymous. "There's absolutely been an uptick over the course of the past few months," he said.

One might imagine that a viewable guarantee would command premium prices in the marketplace, but the demands from advertisers are not being accompanied by a willingness to pay more. "I haven't heard of many examples where sellers have said, 'Hey look, I've been able to increase my rates as a result of offering viewability,'" said the executive. "Buyers have leverage. That's the reality of the market."