If you’re a marketer wanting to maximize ad performance and ROI, you need to understand how ad units work. Ad units are foundational to online advertising, as they determine where and how your ads will be displayed across websites, apps, and video streaming platforms. This guide explains what an ad unit is and breaks down the different ad types, formats, sizes, and placements. I’ll also show you how to optimize your ad units for better engagement and performance.
What Is an Ad Unit?
An ad unit is a specific space on a web page or app that displays various types of ads, such as banner, native, video, and interstitial ads. It often contains code that tells the ad network the size, format, and placement details.
Four Common Types of Ad Units
Ad units come in a variety of types, and understanding their differences can help you choose the right ad format for your campaign. Here are the most common ad unit types:
1. Display Ad Units
Display ad units can appear on websites as static images or rich media-based ads and are usually located in a banner or sidebar format or within the web page content. Many display ad units use standardized sizes, like 250 X 250, or 728 X 90.
2. Video Ad Units
Regular video ads, also known as pre-roll, mid-roll, or post-roll, play before, during, or after video content on a wide range of platforms. They can be very effective for storytelling, as a well-crafted video can evoke emotion from the viewer. However, they can also be disruptive if they delay the content that the viewer is trying to watch.
3. Native Ad Units
Native ads units are designed to blend into the surrounding content. Marketers can do this in various ways: For example, native ad units can be placed within a news or social media feed, on a search results page (appearing like an organic listing), or as a content recommendation widget at the end of an article.
4. Interstitial Ad Units
Interstitial ads are full-screen ads that appear during natural breaks in the content, like between articles or sections of an app. They’re very good at grabbing a viewer’s attention, but can become overwhelming and disruptive if not used selectively.
Ad Unit Formats
Ad unit types and formats are closely related, but different. An ad unit type refers to the category or placement of an ad unit, e.g., display, video, native, interstitial. An ad unit format describes the specific structure of the ad content. Here are some common ad format examples:
Static Image
Static image ad units are simple, and typically use formats like JPG, PNG, or GIF. They can be easily produced and are quick to load.
Rich Media
Rich media ads offer more advanced features, such as video, audio, or other elements that make it easier for viewers to engage with the content. While rich media ads can boost engagement, they usually take longer to load than static image ads.
HTML5
HTML5 is the latest version of the HyperText Markup Language (HTML), the standard language used to create and display web content. Because HTML5 is supported by all modern web browsers and is compatible across all device types, the format is very effective for dynamic, interactive, and mobile-friendly advertising. It’s responsive, too, so you can deliver the same ad to users on a laptop, phone, or tablet. HTML5 ads are often lighter than rich media ads, so they can load faster, which improves the user experience.
Display Ads
Display ads constitute broad category that includes many common ad formats like banner ads (rectangular images), skyscraper ads (tall, narrow ads), and medium rectangles. These are classic examples of ad units, defined by their size and placement on a page.
Carousel Ads
While carousel ads are a more dynamic and interactive format of advertising (allowing multiple images/videos to be swiped through), they are still implemented within a specific, predefined ad space or container on a platform. Each “card” within a carousel ad can have its own headline, description, and call to action, all contained within that single ad unit.
Native Content
Native ads can be considered a type of ad unit as well as an ad format. The latter refers to how native ads look and interact. Essentially, they’re designed to blend seamlessly with the surrounding content by matching its look and feel. Because they are less intrusive than traditional online ads, like video, banner, or pop-up ads, native ads often generate higher engagement and better value for marketers.
Ad Unit Sizes
Digital advertising ad unit sizes have been established by the Interactive Advertising Bureau (IAB), which is an industry organization that works with advertisers, publishers, and technology providers to develop technical standards and guidelines for digital advertising. The table below outlines just a few standard fixed ad unit names and dimensions, along with their typical placements:
| Ad Unit Name | Dimensions (px) | Common Placement |
| Billboard | 970 X 250 | Top of premium pages |
| Half Page | 300 X 600 | Sidebars or interstitial areas |
| Large Rectangle | 336 X 280 | Within content or sidebars |
| Medium Rectangle | 300 X 250 | Within content or sidebars |
| Leaderboard | 728 X 90 | Top or bottom of web pages |
| Skyscraper | 120 X 600 | Sidebars |
While these classic fixed ad unit sizes are still widely used, the industry has moved toward flexible and responsive ad sizing as part of the IAB New Ad Portfolio. These ads are able to adapt their size and specifications to the user’s screen and device.
Ad Unit Placements
Ad placement refers to where an ad appears within a website, app, or video stream. By selecting the best possible placement, you can maximize visibility and user engagement. Below are some common ad placement options:
Above the Fold
Above the fold refers to the portion of a web page or app screen that is visible without scrolling. By placing ad units above the fold, they will typically receive higher impressions and engagement.
In-Content
In-content placement refers to placing ads within articles or other types of content, such as videos. Doing so can lead to higher click-through rates. It also provides marketers with an opportunity to provide contextual relevance.
Sidebar
Sidebar placements are located on the left or right side of a web page, beside the main content. Many desktop environments use sidebar layouts, as there is more horizontal space to work with. When the web page is displayed on a mobile device, the sidebar content usually moves below the main content, or is hidden entirely.
Footer
Ad units in a footer placement are located at the very bottom of a web page or app screen. They usually appear below all of the main content on the page.
How to Optimize Ad Units
Here are some common strategies marketers can use to optimize their ad units and improve ad performance:
Test Different Ad Formats and Dimensions
Consider A/B testing different ad formats to determine which ads resonate best with your audience — never assume that one format works best for all campaigns. By choosing an ad platform that offers AI-powered testing, you can continuously A/B test all your ads, optimizing both targeting and creative in real time.
Prioritize Viewability
Some ad unit types, such as in-content placements and sticky sidebars, tend to remain in view longer. By focusing on these ad units, you may be able to improve performance and boost ROI.
Use Contextual Targeting
Try to run ad units with relevant content in order to improve user engagement. This is where native ad units shine, as they blend into the environment.
Optimize Ads Units for Mobile
According to Google, mobile-friendly websites are prioritized in search results. Also, many advertisers receive the majority of their traffic from people using mobile devices. As such, it’s critical to ensure your ad units are responsive and perform well on mobile. For example, the 320 X 50 ad unit is designed for small screens, as are many native units.
Key Takeaways
Ad units are critical components of digital advertising. They define where and how ads are displayed across websites, apps, and streaming platforms, and come in various types and sizes, based on IAB standards. Remember that placement plays a key role in the performance of ad units. You can also optimize ad units by A/B testing, focusing on contextual relevance, and ensuring they are responsive: Over time, and with the right strategies, you can generate more impressions, boost viewer engagement, and improve your campaign performance.
Frequently Asked Questions (FAQs)
What are some common ad unit examples?
Popular ad units include the 120 X 600 Skyscraper, often displayed in sidebars, a native video appearing in a social media feed, or a 15-second video ad that plays before a YouTube video.
How do you create an ad unit?
The process for creating an ad unit is fairly straightforward, but will differ slightly based on the ad platform you’re using (e.g., Realize or Google Ad Manager). You will typically start by setting your ad unit size, format, and placement. Once that’s done, you can generate the ad unit code and place the code on your website or app. Note that you don’t always have to manually embed ad code: Many modern ad platforms support dynamic or automated placement methods.
What is an ad unit code?
An ad unit code is an HTML or JavaScript snippet that tells the ad server where to serve an ad on a web page or app, and how to render it. The code contains information such as the ad size, placement ID, and targeting parameters. When the web page loads, the ad unit code communicates with the ad server or exchange to retrieve and display a relevant ad.
