In-app mobile advertising is exactly what it sounds like: adverts shown inside mobile applications rather than on the mobile web. When a banner sits at the bottom of a weather app, a video plays between levels of a game, or a sponsored listing appears in a shopping app's feed, that is in-app advertising at work. It is one of the largest corners of digital advertising, because it is where attention actually lives: UK adults now spend far more of their phone time inside apps than in mobile browsers. For businesses, that means in-app placements are often the most direct route to a phone screen. This guide explains what in-app advertising is, how it works behind the scenes, the formats available, and how a UK small business can use it sensibly.
The basic idea is simple. App developers need revenue, and most apps are free, so they sell space inside their apps to advertisers. Advertisers buy that space to reach people in a highly engaged, full-screen environment. A network or platform sits in the middle, matching adverts to apps and audiences. What makes in-app different from web advertising is the environment: apps know a lot about context and behaviour (with user consent), the formats are built for touchscreens, and engagement rates are typically higher than equivalent mobile web placements because the user is focused, not tab-hopping.
The main in-app ad formats
There are five formats you will encounter, and each suits different goals.
Banner ads are the small rectangular units at the top or bottom of the screen. They are cheap and unobtrusive but easy to ignore, so they work best for broad awareness or retargeting where frequency matters more than impact.
Interstitial ads are full-screen placements that appear at natural transition points, such as between game levels or when moving between app sections. They command attention and get strong click-through rates, but they interrupt the experience, so overuse annoys users and some apps limit them.
Rewarded video is the standout performer for engagement. The user watches a short video (usually 15 to 30 seconds) in exchange for an in-app reward like extra lives, premium features, or virtual currency. Because the user opts in, completion rates are very high, often above 70%. This format is dominant in mobile gaming but increasingly used in lifestyle and utility apps.
Native ads match the look and feel of the app around them, appearing as just another item in a feed. They perform well because they do not feel like adverts, though they must be clearly labelled as sponsored to comply with UK advertising rules.
Playable ads let users try a mini interactive demo, most commonly for other apps and games. They are expensive to produce but qualify intent brilliantly: someone who plays the demo is far more likely to install.
How it works behind the scenes
The mechanics will feel familiar if you have run any programmatic advertising. App developers integrate a software development kit (SDK) from an ad network or mediation platform into their app. That SDK reports available ad space, "inventory", to the network in real time. When you launch a campaign on a platform such as Google App campaigns, Meta, TikTok, or a dedicated in-app network, your ad enters auctions for that inventory. The winning ad is served in milliseconds, targeted according to the criteria you set.
Targeting in-app works much like other digital advertising: demographics, interests, location, device type, and operating system. What is distinctive is contextual and behavioural depth. An advertiser can target users of specific app categories (fitness apps, finance apps, parenting apps), and with consent, richer signals such as past in-app purchases. Since Apple's App Tracking Transparency changes, targeting on iOS relies more on aggregated and contextual signals than on individual tracking, which has pushed advertisers toward broader audience strategies and better creative rather than hyper-granular targeting.
Measurement typically centres on impressions, click-through rate, video completion rate, installs (for app advertisers), and post-install events such as sign-ups or purchases. For non-app advertisers, the goal is usually driving traffic to a mobile site or generating leads, so conversion tracking via a mobile measurement partner or platform pixel is essential. Without it, you are buying attention blind.
Should a UK small business use in-app advertising?
It depends on your goal and your customer. In-app advertising excels at reaching people during leisure time in an attentive state, which suits consumer brands, local services, entertainment, and ecommerce. It is less natural for B2B, though not useless: decision-makers still play games and check weather apps. The honest caveat is creative: small static banners get ignored, so budget for proper mobile creative, short vertical video especially. A repurposed desktop display banner will underperform and you will conclude the channel does not work, when the creative was the problem.
Start with the platforms you may already use. Google App campaigns and Meta's Audience Network both serve in-app inventory and can be run with modest budgets, letting you test whether your audience responds before committing to specialist networks. Set a clear test budget and a time limit, define success in advance (cost per lead, cost per acquisition, or even just engaged visits), and compare against your other channels on equal terms. Watch for invalid traffic too: in-app has historically attracted more accidental clicks and fraud than other channels, so use a platform with solid fraud filtering and check placement reports.
Also mind compliance. Ads must be clearly distinguishable from app content under ASA rules, and any data-driven targeting must respect UK GDPR consent requirements. Reputable networks handle much of this, but the advertiser remains responsible for the claims in the creative.
In-app mobile advertising is not a novelty channel; it is where a huge share of mobile attention already sits. Used with good creative, clear targeting, and honest measurement, it can be a cost-effective addition to a broader paid media mix. If you are already running paid campaigns and want to extend them properly, our PPC advertising team plans and manages campaigns across in-app and other placements, and you can get in touch to discuss what fits your goals. New to paid media entirely? Start with our beginner's guide to PPC for UK small businesses.
FAQs
What is in-app advertising in simple terms?
It is advertising displayed inside mobile apps rather than on websites. Examples include banners in a news app, video ads between game levels, and sponsored posts in a shopping app's feed. App developers earn revenue from the space; advertisers buy access to an engaged audience.
How much does in-app advertising cost?
Costs vary widely by format, targeting, and platform. Banner inventory can be very cheap per thousand impressions, while rewarded video and playable ads cost more but deliver far higher engagement. Most major platforms let you start with small daily budgets, so testing is affordable. Agree your success metric before spending.
Is in-app advertising effective for small businesses?
It can be, particularly for consumer-facing businesses with strong mobile creative. Short vertical video tends to outperform static banners significantly. It is best used as part of a mix alongside search and social rather than as your only channel, so you can compare performance fairly.
What is the difference between in-app ads and mobile web ads?
In-app ads appear inside applications; mobile web ads appear in mobile browsers. In-app environments typically offer higher engagement, richer behavioural signals (with consent), and formats designed for touchscreens, while mobile web offers broader reach across sites. Many campaigns run across both.
Do in-app ads work on both iPhone and Android?
Yes, all major platforms serve both iOS and Android inventory, and you can target or exclude either operating system. Note that iOS targeting is less granular than it once was due to Apple's privacy changes, so creative quality and broader audience strategies matter more on iPhone.
