Run of Site (ROS) Advertising: The Ultimate Guide for AI and SEO Experts

Run of Site, often abbreviated as ROS, is a common digital advertising strategy that allows advertisers to place their ads across an entire website rather than in specific sections or targeting certain audience segments. In this ultimate guide, we‘ll take an in-depth look at what ROS advertising entails, explore its origins and evolution, examine the benefits and best practices, and discuss what the future may hold for this important approach to online ad placement.

What is Run of Site (ROS) Advertising?

In the simplest terms, Run of Site advertising refers to the practice of displaying ads on any and all pages of a website, without restrictions based on the content of those pages or the specific characteristics of the audience viewing them. When an advertiser buys ROS ad placements, their ads are eligible to appear anywhere on the site, alongside a wide variety of content.

This is in contrast to more targeted advertising approaches, where ads are only shown on certain pages or to certain users based on factors like:

  • Contextual relevance (e.g. showing car ads on auto-related content)
  • Demographics (e.g. age, gender, income, etc.)
  • Geographic location
  • Past browsing behavior or interests
  • Retargeting based on previous interactions with the brand

With ROS, the focus is on maximizing reach and getting as many ad impressions as possible across the site‘s entire audience. Advertisers often use ROS as a brand awareness strategy to introduce themselves to new potential customers, drive top-of-funnel engagement, and cast a wide net with their messaging.

How Does ROS Ad Serving Work?

To understand how ROS advertising actually gets delivered to users, it‘s important to have a basic understanding of ad serving technology. Ad serving refers to the process of delivering ads to users‘ browsers or apps as they navigate through a website or use an application.

Most modern ad serving uses a technique called "real-time bidding" (RTB), which is a type of programmatic advertising. With RTB, advertisers bid on ad impressions in real-time, as a user is loading a webpage. The ad server then selects the winning bid and serves the corresponding ad creative to the user.

Here‘s a simplified overview of how this process works:

  1. A user navigates to a webpage that has ad slots available.
  2. The webpage sends a request to an ad server, along with information about the user (such as their location, device type, and any available targeting data).
  3. The ad server analyzes the available ad inventory and sends bid requests to multiple advertisers or demand-side platforms (DSPs).
  4. Advertisers or DSPs submit bids for the impression based on their targeting criteria and campaign goals.
  5. The ad server selects the winning bid and sends the corresponding ad creative back to the webpage.
  6. The webpage displays the ad to the user.

All of this happens in a matter of milliseconds, allowing for a seamless user experience and efficient ad delivery.

For ROS campaigns, the process is similar, but with a few key differences:

  1. Rather than targeting specific pages or audience segments, ROS campaigns are eligible to serve ads on any and all ad slots across a website.
  2. ROS campaigns are often given a lower priority in the ad server compared to more targeted campaigns, meaning they may only serve if there are no higher-value targeted ads available for a given impression.
  3. ROS pricing is typically lower than targeted campaigns on a cost-per-thousand-impressions (CPM) basis, since the inventory is considered less valuable.

Here‘s a visual representation of how ROS ads fit into the broader ad serving ecosystem:

ROS Ad Serving Diagram

As you can see, ROS campaigns essentially act as a "catch-all" for ad impressions that are not claimed by higher-priority targeted campaigns. This allows publishers to maximize their ad revenue and ensures that advertisers can still achieve broad reach and awareness even if they don‘t have the budget or data for more sophisticated targeting.

The Origins and Evolution of ROS

To truly understand ROS and its role in the digital advertising ecosystem, it‘s helpful to look back at the early days of online ads and how the approach originated. In the 1990s, as the first publishing websites began to monetize their content with advertising, the concept of ROS emerged as the default option for ad placement.

At the time, web traffic was limited and online audiences were seen as more homogenous compared to offline channels like print or television, where ads could be targeted to different demographics or interest groups based on the publication or program where they appeared. With less ability to segment audiences, advertisers embraced ROS as an efficient way to get broad exposure for their brands.

As the internet grew and evolved, so too did online advertising technology and practices. With the rise of ad networks and exchanges in the early 2000s, advertisers gained the ability to reach users across multiple websites through a single platform, rather than having to negotiate individual ROS deals with each publisher.

The advent of programmatic advertising and real-time bidding (RTB) in the late 2000s and early 2010s marked another major shift, as advertisers could now use data and algorithms to automatically target specific audience segments at scale. This led to a decline in ROS buying as brands pursued more granular targeting options.

However, ROS has remained an important part of the digital ad mix to this day for several reasons:

  • Brand building: ROS is still seen as an effective way to generate broad awareness and introduce a brand to new audiences who may not be reached through targeted campaigns.

  • Filling inventory: Publishers often use ROS to monetize inventory that isn‘t sold through more targeted channels, ensuring they are generating as much ad revenue as possible.

  • Balancing reach and efficiency: Advertisers may include an ROS component in their overall media mix to maintain reach while also running more targeted, higher-ROI campaigns.

In recent years, there has also been a resurgence of interest in ROS with the growth of native and sponsored content advertising, which is often purchased on a site-wide basis to integrate a brand‘s messaging into a publisher‘s editorial environment.

According to a 2020 survey by eMarketer, nearly 60% of US digital media professionals said they used ROS advertising as part of their marketing mix, highlighting its continued relevance and popularity.

The Benefits of ROS Advertising

So why do advertisers continue to allocate budget to ROS campaigns with all the advances in ad targeting and automated media buying? There are several key benefits to this approach:

  1. Reach and scale: By nature, ROS campaigns are designed to reach the widest possible audience on a given website. For advertisers looking to drive massive awareness and get as many ad impressions as possible, ROS is often the most efficient option.

  2. Cost efficiency: Compared to more targeted ad buys, ROS inventory is typically less expensive on a cost-per-thousand impressions (CPM) basis since it is seen as less valuable than an ad shown to a specific high-value audience segment. This allows advertisers to stretch their budgets further.

  3. Brand safety: With ROS placements, advertisers know they will be appearing on a reputable publisher‘s site and not on low-quality or potentially problematic pages. This is especially important for brands concerned about their ads showing up next to objectionable content.

  4. Publisher relationships: Buying ROS inventory directly from a publisher helps advertisers build closer partnerships and gain access to premium first-party data and high-impact creative executions.

  5. Ease of execution: ROS campaigns are often simpler to plan and traffic than more complex data-driven or hyper-targeted campaigns, making them a good choice for advertisers with limited time or resources.

To illustrate the cost efficiency of ROS compared to targeted advertising, consider the following data from a 2019 report by AdStage:

Ad Type Average CPM
ROS (Run of Site) $2.80
Behavioral Targeting $4.20
Contextual Targeting $3.50
Geographic Targeting $3.00
Retargeting $5.50

As you can see, ROS has the lowest average CPM of any ad type listed, making it an attractive option for advertisers looking to maximize their reach on a budget.

Best Practices for Effective ROS Campaigns

Of course, not all ROS campaigns are created equal. To get the most out of this approach, advertisers should follow these best practices:

  • Define clear goals: As with any campaign, start by outlining what you hope to achieve, whether it‘s driving brand awareness, increasing site traffic, or generating leads. This will inform your creative approach, KPIs, and overall strategy.

  • Choose the right publishers: Look for reputable sites that align with your brand values and target audience interests. Consider factors like the publisher‘s content mix, audience demographics, and ad specs to ensure your ads will resonate.

  • Use engaging creative: Since ROS ads are typically served to a wide audience, it‘s important to use eye-catching visuals and compelling copy that will grab people‘s attention and communicate your key message quickly. Consider using interactive formats like video or rich media to stand out.

  • Implement frequency caps: To avoid oversaturating users with your ads, set frequency caps to limit the number of times an individual will see your ad in a given time period. This helps manage brand fatigue and maintain a positive user experience.

  • Test and optimize: As with any digital campaign, be sure to A/B test different ad creative, calls-to-action, and landing pages to see what resonates best with your audience. Use the insights gained to continually optimize your ROS strategy for better performance over time.

Here‘s an example of how an advertiser might set up an ROS campaign with relevant keywords for SEO:

Campaign: Summer Sneaker Sale

Ad Copy: Get 20% off the hottest sneaker styles of the season! Shop now for the best selection. [Relevant Keywords: summer sneakers, sneaker sale, discount sneakers]

Landing Page: A dedicated page on the advertiser‘s e-commerce site featuring a curated selection of discounted summer sneakers, with optimized product descriptions and meta tags including relevant keywords.

By incorporating relevant keywords into the ad copy and linking to an optimized landing page, the advertiser can improve their chances of driving organic search traffic in addition to the awareness and engagement generated by the ROS campaign.

ROS and SEO: A Winning Combination

Speaking of SEO, it‘s worth exploring how ROS advertising can complement and enhance an advertiser‘s search engine optimization efforts. While paid search advertising (such as Google Ads) is often the go-to tactic for driving short-term search visibility and traffic, ROS can play an important role in building long-term organic search equity.

Here are a few ways ROS and SEO can work together:

  1. Increasing brand awareness and search demand: By exposing a wide audience to your brand through ROS campaigns, you can generate more branded search queries and direct traffic over time. As more people become familiar with your brand, they are more likely to search for you by name and click through to your site from organic search results.

  2. Driving backlinks and referral traffic: When users click on your ROS ads and visit your site, they may be more likely to link back to your content or share it on social media. These backlinks and referral traffic can help improve your site‘s domain authority and search rankings over time.

  3. Supporting content marketing efforts: ROS campaigns can be a great way to amplify and distribute your brand‘s content marketing assets, such as blog posts, infographics, and videos. By driving more traffic and engagement to your content, you can improve its chances of ranking well in search results for relevant keywords.

  4. Providing keyword and audience insights: By analyzing the search queries and audience data associated with your ROS campaigns, you can gain valuable insights into the keywords and topics that resonate with your target audience. These insights can inform your SEO keyword research and content strategy, helping you create more relevant and engaging content that ranks well in search results.

For example, let‘s say a fitness apparel brand runs an ROS campaign promoting a new line of yoga pants. By analyzing the search queries that drive traffic to the campaign‘s landing page, they may discover that "high-waisted yoga pants" and "yoga pants with pockets" are popular keywords among their target audience. They could then create new blog content or product pages optimized around these keywords to capture more organic search traffic.

The Future of ROS Advertising

Looking ahead, it‘s clear that ROS will continue to play an important role in the digital advertising landscape, even as more advanced targeting and programmatic technologies gain adoption.

One potential area of growth is in the realm of connected TV (CTV) and over-the-top (OTT) advertising. As more consumers shift their viewing habits to streaming platforms, advertisers are looking for ways to reach these audiences at scale. ROS-style buys that allow for broad reach across a platform‘s entire user base are an attractive option.

Another trend to watch is the rise of first-party data and the decline of third-party cookies. With the phasing out of cookies in Chrome and other browsers, publishers are increasingly looking to monetize their first-party audience data through direct deals with advertisers. ROS buys provide a way for brands to access this valuable data while still achieving broad reach.

Finally, advances in machine learning and AI are opening up new possibilities for ROS optimization. By analyzing data on ad performance, user behavior, and content engagement, advertisers can gain insights into which placements and creative approaches are most effective for driving their KPIs. This data-driven approach allows for a more nuanced approach to ROS that combines the benefits of reach and targeting.

As Gartner predicts, by 2024, 75% of all digital advertising will be powered by AI and machine learning. This trend is likely to have a significant impact on ROS advertising, as AI-powered optimization and targeting become more sophisticated and accessible to advertisers of all sizes.


Run of Site advertising has a long and storied history in the world of digital marketing, and it‘s clear that this approach still has an important role to play for brands looking to drive awareness and engagement at scale. By understanding the benefits and best practices of ROS, and keeping an eye on emerging trends, advertisers can continue to leverage this tactic effectively for years to come.

As the digital landscape continues to evolve and new advertising challenges and opportunities arise, savvy marketers will undoubtedly find new and creative ways to adapt ROS for their needs. Whether it‘s leveraging AI for optimization, tapping into new channels like CTV, or combining ROS with SEO and content marketing, the possibilities are endless.

The future is bright for this enduring and adaptable approach to online advertising, and we can‘t wait to see how it continues to evolve and drive results for brands of all types and sizes.

So if you‘re looking to build brand awareness, drive engagement, and maximize your digital ad spend, give ROS a try. With the right strategy and execution, it just might become your new secret weapon.

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