By baking new ad blocking tools into their web browsers, Google and Apple have made it clear they don’t like certain types of web ads – in particular, video ads that play with the sound on.

Many consumers probably agree. But it is not welcome news for ad tech companies that profit from video ads that play automatically whether people asked for them or not. For now, there are a lot more questions than answers about how the ad blocking will work and what kinds of ads are going to be affected by the new versions of Google’s Chrome or Apple’s Safari.

But ad tech companies ranging from Appnexus to Rubicon Project to Teads (which was just acquired by the French media giant Altice for $307 million) that have placed big bets on – or raised significant funding toward -building their businesses on so-called outstream ads, are paying close attention. Outstream ads generally refer to video ads that run in non-video parts of content sites, such as in between paragraphs of a text-driven editorial post. (In other words, these are not video ads running within video content. They are video ads stuck on other parts of a web page).

The way these ads are delivered varies. In some cases, they only stream when a person scrolls past them or mouses over them. Often they don’t run with sound unless a person engages with them in some fashion. Some in the ad industry refer to them as “native video” ads. “Publishers who mix text, images and auto-play-sound-on-video will be,” affected, said Tal Chalozin, co-founder and chief technology officer of the ad tech firm Innovid. Premium video publishers such as Hulu, meanwhile, probably won’t be, since – generally speaking – their video ads run alongside video content and only play when people deliberately click on videos. These kinds of ads aren’t being targeted by the new browser-blockers.

Teads executive chairman Pierre Chappaz said that because his company’s ads don’t automatically play with sound, he believes that Apple’s new browser won’t block them. “We have always placed the respect of the user at the heart of all our work,” he said. “Ads should never block or annoy users.”

Consumers may have more options to avoid annoyance-soon. Walter Knapp, CEO at the video at tech firm Sovrn Holdings, said that he expects all the major browsers to follow suit on blocking autoplay video ads with sound. He sees a fundamental challenge with the out stream ad model, one that works in Apple and Google's favor.

"Publishers like the format because it brings in high dollar amounts," he said. "And advertisers like it. But here's the rub. Consumers don't like it."

"Really good video advertising is user-initiated," he added. "What you're going to find is the more publishers push non-user initiated video ads, the more people who install ad blockers. The more that happens, it's mid-sized publishers really get hurt."