Ask five people in ad tech to explain instream vs outstream and you will get five answers, several of them contradictory. The confusion is not academic. It decides which demand can bid on your inventory, what buyers expect to pay and whether readers find your pages tolerable. This post gives clear definitions, sets out the differences that actually matter, and explains when each one belongs on a publisher’s property.
What in-stream means
An in-stream video ad plays as part of a video the viewer chose to watch. There is real content in the player, and the ad runs before it (pre-roll), during it (mid-roll) or after it (post-roll).
The defining feature is content dependency. In-stream needs a video for the ad to attach to. No content, no in-stream. That is why in-stream has traditionally been the preserve of broadcasters, video-first sites and anyone with a library to play.
The viewer’s state of mind matters here. Someone who pressed play has already committed to watching something. An ad in that context is an expected toll rather than a surprise, which is why in-stream tends to hold attention through longer creative.
What outstream means
An outstream video ad appears where there is no video content at all. The player exists only to carry the ad. It might sit between two paragraphs of an article, inside a feed, or as a small floating unit that stays visible while the reader scrolls.
Outstream removed the biggest barrier to video monetization: you no longer need a video library to sell video inventory. A text-first publisher can carry video ads on any article page.
That freedom comes with an obligation. Because nobody asked for the video, outstream has to behave. Start muted, play only when the unit is in view, pause when it leaves, and make the unit easy to scroll past or close.
The differences that matter
Four differences do most of the work when you are deciding between them.
Content dependency. In-stream requires video content. Outstream does not. This alone determines what many publishers can offer.
Viewability behavior. In-stream viewability depends on whether the player is on screen while the ad plays, which is usually a given if the viewer is watching. Outstream units are typically built to only play in view, so they can be well behaved on viewability, but they also live in a scrolling page where the reader may move on mid-ad.
Completion expectations. In-stream tends to sustain longer creative because the viewer is waiting for something. Outstream is better suited to short creative that makes its point quickly, since the reader’s next scroll is always a moment away.
User experience. In-stream sits inside an experience the viewer opted into. Outstream interrupts a reading experience. Neither is inherently worse, but outstream carries a higher duty of care: sound off by default, clear controls, no layout shift when the unit loads.
Buyers price these differences. In-stream is generally treated as a premium environment because of the viewer’s committed attention, while outstream is valued for reach and for placing video in editorial contexts that in-stream cannot reach. Rather than assume a ranking, look at your own placement-level reporting and let it tell you what each position earns on your pages.
When a publisher should use in-stream
In-stream is the right choice when you have video people want to watch, or when you can create it. That covers more publishers than it used to.
Use in-stream when:
- You have a video library, whether produced in-house, licensed or repurposed from social channels.
- You can build a session, so one clip leads to another and a mid-roll has somewhere to sit.
- Video is part of the editorial product, not an add-on, so readers expect to find it.
- You run a news or content app, where a video tab or feed gives the format a natural home. Our news and content apps page covers that setup.
The common objection is production. In practice, social clips, licensed editorial video and AI-generated teasers built from existing articles can fill a player without a dedicated video team, which turns an outstream-only site into an in-stream one.
When outstream is the better fit
Outstream earns its place on text-heavy properties and on pages where a full video experience would be out of character.
Use outstream when:
- You have no video for a given section and no plans to make any.
- The page is a quick read, where a session-based player would not hold anyone.
- You want incremental video revenue on long-tail article pages without rebuilding the template.
- You are testing demand before committing to a video product at all.
Be honest about ad load when you do. An outstream unit added to a page that already carries several display slots competes with them for the same glance, and the page gets worse for everyone. The stronger version of outstream replaces a low-value display unit rather than joining it.
Running both without making a mess
Most publishers end up with both, and that is fine as long as the roles are clear. Section-level rules work better than site-wide ones: in-stream where there is video and a reason to stay, outstream where there is not.
A few habits keep it tidy:
- Give each placement its own reporting line, so you can see what it earns and what it costs in page speed.
- Cap how many video units a single page can load, regardless of type.
- Keep creative expectations aligned, with shorter spots for outstream and room for longer ones in-stream.
- Run A/B tests when you change placement or ad load, and watch scroll depth alongside revenue.
The demand side is the same either way. Both formats trade on OpenRTB with VAST creative, both can run through Prebid Server, and both can draw on curated demand alongside a publisher’s own partners. What changes is the environment you are selling, not the plumbing. If you want the buyer’s perspective on why that environment matters, the advertisers page sets it out.
Key takeaways
- In-stream plays inside video content the viewer chose; outstream runs where there is no video content at all.
- Content dependency is the first fork in the road, and it decides what many publishers can offer.
- In-stream suits longer creative and committed attention; outstream suits short creative and careful behavior.
- Use in-stream where you have or can create video, and outstream on text-heavy pages, ideally replacing a weaker display unit.
- Run both with section-level rules, per-placement reporting and A/B tests before scaling.
Vortex Media supports in-stream and outstream alongside vertical players, floating units and in-player display, on web and in apps. See how the pieces fit together on the publishers page.
