TL;DR

• Liner sought to monetize its free users through contextual ads that complemented their academic research

• When legacy ad formats couldn’t adapt quickly enough, Liner deployed Koah’s lightweight SDK to serve users innovative and highly relevant ads 

• Koah is now a core pillar of Liner’s monetization engine, driving consistently higher CTR and coverage 

About

Liner is a global AI search engine that delivers precise answers backed up by reliable, line-by-line citations. Trusted by over 12 million students and researchers in 220+ countries, Liner has been featured three consecutive times on Andreessen Horowitz’s list of top GenAI consumer companies and raised KRW 44 billion (~$32M USD) in cumulative funding.

Challenge

Monetization Was Essential for Growth—But Traditional Ads Didn’t Suit Liner’s Academic Audience 

Liner’s citation-based answers and low hallucination rates make it the ideal AI-powered search engine for PhDs, students, and postdocs. This trust-first approach has enabled the app to convert record numbers of its global users into paid subscribers. 

Liner CEO Luke Jinu Kim knew that subscriptions would only be one part of building truly sustainable, long-term growth. That’s why he set out to monetize Liner’s popular free tier with ads.

The problem? Finding an ad format fit for LLM interfaces.

Aware that no purpose-built options existed yet, Luke deployed GoogleAdSense units across web and mobile surfaces. As he had suspected, these traditional ad formats didn’t match Liner’s carefully designed user experience. Not only were the placements visually disruptive, but the ads slotted into them rarely related to the academic queries they accompanied.

“Every aspect of our user experience is crafted with our academic audience in mind. If we disrupt a user studying for an exam with a loud ad, they’ll bounce.” – Luke Jinu Kim

Moreover, Luke had no easy way to iterate on his efforts because Google provided minimal visibility into why each ad did or didn’t resonate with audiences.

He wished someone would invent a contextual ad technology that could unlock meaningful revenue without jeopardizing the user experience. One that would seamlessly embed itself into queries, suggest relevant products, and provide full performance transparency.

As it turned out, Luke didn’t have to wait long. Soon after, a founder friend introduced him to a team building the exact technology he’d envisioned: Koah. And just like that, a lasting partnership began.

“Legacy ad formats aren’t equipped to help us meaningfully monetize our AI search platform. Koah is miles ahead.” – Luke Jinu Kim

Solution

Koah’s Inline, Contextual Placements Engage and Convert at Scale

Koah’s LLM-native ads were exactly what Liner needed to maximize revenue per traffic while retaining its strong academic base.

Onboarding began with a quick SDK build. Because Liner’s mobile app is so popular, the Koah team tailored their SDK for mobile placements in addition to web. With this integration, Luke began deploying context-aware ads from Koah’s highly curated advertiser network and quickly saw tangible revenue gains. 

To ensure every placement complements—and even enhances—the user experience, Koah enables Luke’s team to test several never-before-seen formats, including:

• Prefix and suffix placements above and below AI answers

• Inline ads within AI answers

• Sponsored follow-up questions

• Sponsored data sources next to citations

Koah makes it easy for Luke and Allan, Liner’s Head of Ads, to measure the impact of this experimentation. Allan meets with the Koah team weekly to discuss how each format is performing across key metrics, including coverage, CTR, RPS, and RPM.

While the highest performers have been the prefix placements and sponsored data sources—which boast a 20% CTR—every ad format and advertising partner is precisely paired with the query. A university student studying for finals may see a prefix placement for an AI-powered study tool, while a researcher exploring the latest publications is served a sponsored citation from a trusted academic institution—each precisely aligned to the user’s intent. This deep commitment to relevance prevents churn and maintains trust.

“If you want to succeed in answer engine marketing, you have to test relentlessly. And with Koah’s constant support, we can take bigger swings.” – Allan, Head of Ads at Liner

Luke and Allan both appreciate how collaborative the partnership has remained over time. Whether Allan wants to make small tweaks to a mockup or overhaul it entirely, the Koah team quickly integrates the feedback into their UI renderings and ensures the final product reflects his expert design vision.

The partnership is paying off for Liner. As Koah’s Publisher Dashboard reports, CTR and surface area are both consistently rising. These encouraging trends have given Luke and Allan the confidence to send an ever-greater share of their web and mobile traffic to Koah. AI monetization is still a moving target, but they both know they’ve found the ideal partner to help them succeed at it.

“Koah’s fast execution, iterative partner support, and real-time metrics help us understand exactly what resonates with our users and why. This rapid learning cycle is why performance is continuously improving.” – Allan

Results

A Powerful Monetization Framework and Rapidly Rising CTR

With Koah, Liner upgraded its monetization model for the LLM era, generating revenue without sacrificing its trustworthy user experience. With this new revenue channel, the company has more flexibility to ship new innovations that supercharge information discovery for millions of academic users.

The results:

• 122% CTR lift

• 84% increase in surface area served monetized ads

• 454% boost in average DAU

The Liner team is excited to continue ramping up the partnership with Koah. Allan is currently strategizing with Koah on photo and video ad formats to serve users during load periods. While AI search hasn’t yet evolved to accommodate these rich placements—which promise enormous eCPM potential—Allan knows that Koah is at the forefront of their development.

“Koah isn’t just the best partner for answer engine marketing; they’re the best partner I’ve worked with, full stop. I know there’s so much more we can build together.” – Allan