The news: Reddit and mobile apps were the fastest-growing US ad channels in Q3, showing their emerging importance to advertisers.

Ad spend on Reddit increased 46% YoY, per Sensor Tower’s Q3 Digital Market Index report, and mobile app ad spend grew 42%. Social networks still account for 72% of ad spend, largely driven by Meta platforms, though total spending on social rose just 11% YoY.

Digging into the data: Instagram remained a bright spot for Meta with 22% YoY growth, while TikTok, Facebook, X, and Snapchat saw ad spend rise by less than 10%. That suggests those apps are nearing saturation point. Diversifying budgets into Reddit and mobile apps could help reduce over-reliance on mature platforms like Meta and TikTok.

Although Reddit remains relatively small in total ad spend—$338 million in Q3 compared with Facebook’s $9.2 billion and Instagram’s $7.8 billion—the rapid growth in investment indicates that advertisers are finding value in niche communities, high-intent audiences, and increasing usage.

Nearly half (48%) of US adults under 30 have used Reddit, up from 36% in 2021, per Pew Research, and the platform is working to monetize that user base. In May, it expanded its ad product offerings to include Dynamic Product Ads that deliver personalized, context-aware ad experiences.

What it means for marketers: Reddit is becoming a high ROI opportunity for early movers. Its growth suggests that highly engaged micro-communities (subreddits) are offering more precise targeting and less competition. That makes Reddit a strong testing ground for community-based and brand awareness campaigns for consumers who are actively looking to discover new content and products.

If mobile app ad spending growth continues, it could outpace TikTok or YouTube in the future, per Sensor Tower. This comes from a steady rise in time spent in-app, improved metrics around app-install tracking, and the commerce-friendly inventory available across gaming, retail, and utility apps.

What marketers should do: Diversify spending beyond legacy social platforms and invest in Reddit and mobile apps to find engaged, intent-driven consumers.

• On Reddit: Target subreddits where people actively seek product advice and recommendations, and establish a brand presence so customers can interact, post reviews, and increase organic discovery.
• On apps: Experiment with vertical-specific placements, like shopping apps for retail brands, and treat app ads as a way to offset Meta’s and TikTok’s saturation with fresh reach.