Out-of-home advertising, from fixed screens to moving ones

By Melih Koray, Marketing, Firefly · Published August 10, 2026

Out-of-home advertising is any ad placed outside the home, from printed billboards to digital screens. US OOH revenue reached a record $9.46 billion in 2025, with digital formats at 36.3% of that total. Most guides assume the screen stands still. A growing share of it moves.

This guide covers the category as a whole — what the formats are, how they are bought, how audiences are counted. It differs from the other explainers you will find in one respect: it does not assume the ad surface is bolted to something. Roughly a third of the inventory in this market is attached to a vehicle, and almost every published introduction to out-of-home skips that fact or files it under "specialty."

What is out-of-home advertising?

Out-of-home advertising, usually shortened to OOH, is advertising that reaches people while they are outside their homes. Billboards, bus sides, subway platforms, mall screens, stadium boards, vehicle wraps and truck displays all sit inside the definition. The common thread is not the format but the setting: the audience is out in public, moving, and not choosing to look.

That last part matters more than it sounds. Nobody scrolls to an out-of-home ad, and nobody can be retargeted into looking at one twice on purpose. The medium is bought on presence rather than attention capture, which is why its measurement question — how many people had a reasonable opportunity to see this — looks nothing like the click-based questions asked of digital media.

How big is the out-of-home market?

US out-of-home advertising revenue reached $9.46 billion in 2025, up 3.6% year over year, according to the Out of Home Advertising Association of America. That result extended the industry's growth streak to nineteen consecutive quarters.

Two numbers inside that total are worth separating. Digital out-of-home accounted for 36.3% of revenue and grew 10.5% — roughly three times the pace of the category. And transit was the fastest-growing segment for the second consecutive year, up 9.2%. Both of those lines describe inventory that is either screen-based, mobile, or both.

What are the main out-of-home formats?

The industry's traditional answer is four buckets: billboards, transit, street furniture and place-based. It is a workable list for fixed sites and a poor one for everything else, because it sorts inventory by where it is installed — which stops being a useful question the moment the inventory drives away.

A more honest split separates three things that the standard vocabulary jams together: what the ad surface is, what carries it, and how those carriers are deployed. Below is that taxonomy applied to the 3,783 documented campaign frames in the archive on this site.

Ad surface

Carrier

A third facet, deployment, describes how many carriers work together and how they are routed — a single truck parked at a venue is a different media buy from forty wrapped cars circulating a downtown grid, even when the surface and the vehicle are identical.

Counts above reflect campaigns documented in this archive. They are evidence that a format ran, not a claim about what is available to book today.

What changes when the screen moves?

Everything downstream of "where is it." A fixed panel occupies one coordinate for the length of the campaign. A vehicle-mounted screen occupies a route, and the route is a variable you can set.

This is the part most category explainers get wrong by omission. They describe DOOH as "digital billboards" and then apply fixed-panel logic to every screen in the market, including the ones on wheels. The mechanics are covered properly on the page about how out-of-home impressions are measured.

How is out-of-home actually bought?

Three buying units cover almost everything in the market, and confusing them is how budgets get compared incorrectly.

Posting period

The traditional unit for printed inventory. You buy a specific site for a block of time — commonly four weeks — and your poster is the only thing on it for the whole block. Production and installation have to be scheduled, so decisions get locked weeks before anything appears. What you are buying is exclusive occupancy of a physical space.

Share of loop

The standard unit for digital screens. A screen runs a loop of several ads, and you buy a slot in that loop across a set of screens for a set period. If the loop holds eight spots and you have one, your ad is on screen an eighth of the time. Nothing is printed, so creative can be changed mid-flight and different creative can run at different hours on the same screen.

Programmatic impressions

The newest unit, and the one that behaves most like the rest of digital media. Instead of buying named sites, you buy delivery against an audience through a demand-side platform, and the system decides which screens serve it. It brings audience targeting and mid-flight optimisation, and it costs you the certainty of knowing exactly which locations your brand appeared on.

Mobile inventory can be sold under any of the three, which is precisely where planners get tripped up. A four-week booking on a wrapped fleet looks like a posting period on the invoice, but the thing you bought is a set of routes, not a set of coordinates. Same paperwork, different product.

How are out-of-home audiences counted?

Out-of-home does not count clicks, so it counts opportunity. The industry measurement body in the US is Geopath, which describes itself as the OOH industry standard for audience location measurement. A fixed unit's estimate starts from how many people move past its location and narrows to how many of them plausibly could have seen it.

Mobile inventory does not fit that shape cleanly, because there is no single location to count past. That is a methodology problem rather than a marketing one, and pretending otherwise is how buyers end up comparing two numbers that were built from different questions.

Who do you actually buy from?

Five different kinds of company will all answer the phone when you say you want to run out-of-home, and they sell genuinely different things: media owners with their own inventory, specialists who run one format across markets, supply-side platforms that make inventory programmatically available, demand-side platforms that buy across owners, and agencies that plan across everything. Picking the wrong layer is the most common and most expensive planning mistake in this category.

The structure, the money flow and a decision tree for which layer to call are laid out on the page about how the out-of-home market is organised.

Where does documented evidence fit in?

Out-of-home has a proof problem. Almost every vendor page in the category illustrates itself with renders — a mockup of a billboard, a car wrap composited in Photoshop. Renders show what a format could look like under ideal light on an empty street.

The archive behind this site takes the other approach: 3,783 photographs of campaigns that actually ran, covering 603 brands across 21 US markets between 2020 and 2026. Digital surfaces alone are documented in markets including New York, San Francisco, Las Vegas, Los Angeles, Chicago. You can browse the archive by format, market and year.

Of those frames, 459 carry a source date that does not parse cleanly and are published without a year rather than with a guessed one.

What makes out-of-home creative work?

Reading conditions, mostly. The viewer is walking, driving or waiting, the surface is at a distance, and the exposure lasts seconds. Every craft rule in the medium follows from that: few words, high contrast, one idea, a brand mark that survives being glanced at rather than read.

Moving surfaces tighten the constraint further, because the viewer and the surface are often travelling at different speeds and the geometry keeps changing. A layout that reads well head-on can be unreadable at an angle. Wrap designs also have to survive the shape of the vehicle — doors, wheel arches and windows cut through artwork in ways a flat panel never does.

One habit worth dropping: putting a QR code on fast-moving inventory and calling it a response mechanism. It is a check-box, not a plan. If the audience is in traffic, they are not scanning anything.

Common planning mistakes

• Treating all DOOH as digital billboards. Screen-based does not mean stationary, and the measurement assumptions differ.
• Comparing impression counts built on different methods. A fixed-panel estimate and a mobile-unit estimate are not interchangeable line items.
• Buying a format before deciding the geography. If the target area is a corridor rather than a point, fixed inventory forces you to approximate it with several sites.
• Writing copy for a reader who is sitting down. Legibility at distance and speed governs almost everything about creative in this medium.
• Skipping local regulation. Mobile formats in particular are governed by city ordinances that vary enormously and are rarely mentioned in a sales conversation.

Where to go next

If you are planning a campaign, the two pages that answer the questions buyers actually get stuck on are how impressions are measured and how the market is structured. If you want to see what the formats look like in the field rather than in a mockup, start with the campaign archive.