In-app purchases: This is one of the most common and effective monetization strategies for mobile apps. With in-app purchases, you allow users to purchase additional content, features, services or items within your app. Some common examples of in-app purchases include:

Removing ads: You can offer an option for users to pay a one-time fee to remove ads from showing up in your app.

Virtual currencies: Games often use virtual currencies like coins or gems that users earn by playing the game but can also purchase more of using real money. The currencies are then used to purchase power-ups, characters, levels etc.

Subscriptions: You can create subscription plans where users pay a monthly/annual fee to unlock premium features or get unlimited access to certain content/services in your app. Common subscription durations are 1 month, 6 months or 1 year.

Additional content: Sell expansions, additional levels, characters, maps, tools etc. as in-app purchases to enhance the core app experience.

Consumables: Offer items that get used up or depleted over time like bonus lives in a game so users have to keep purchasing them.

Some tips for optimizing in-app purchases include having a clear free trial experience, bundling related items together, using sales and discounts strategically, and upselling and cross-selling other relevant products. Analytics on player segments is also important to target the right users.

Paid apps: Instead of making the core app free with optional in-app purchases, you can also develop a paid app model where users pay an upfront one-time fee to download and access all core app functionality without any ads or limitations.

The paid app approach works well for apps with very high perceived value, complex utilities, content creation or productivity tools where a subscription may not make sense. Some artists, writers and creative professionals also prefer a simple one-time purchase model over subscriptions. It limits the potential user base and monetization compared to free-to-play models.

Advertising: Showing ads, especially full-screen interstitial ads, is one of the most widespread methods to monetize free apps. With mobile advertising, you can earn revenue through:

Display ads: Banner, text ads shown within the app UI on screens like level loads, between sessions etc.

Video ads: Pre-roll or mid-roll video ads displayed before or during video playback within the app.

Interstitial ads: Full-screen takeover ads shown when transitioning between screens or game levels.

It’s important to balance ad frequency, placement and types to avoid frustrating users. Analytics on ad click-through and engagement helps optimize monetization. You can also explore offering ad-free experiences through in-app purchases. Various ad mediation SDKs like Google AdMob, Facebook Audience Network help manage multiple ad demand sources.

Affiliate marketing: Promote and earn commissions from selling other companies’ products and services through your app. For example, a travel app can recommend hotels and flights from affiliate partners and earn a percentage of sales. Likewise, an e-commerce app can promote trending products from affiliate retailers and brands.

Successful affiliate programs require building strong app audiences, complementary product matching and transparent affiliate disclosures. Analytics helps track what affiliates drive the most sales. Affiliate marketing works best for apps with large, engaged audiences with an innate interest in purchasable products and services.

Referral programs: Encourage your app’s existing users to refer their friends and family by sharing referral codes. When the referred users take a desired action like completing onboarding, making a purchase etc., both earn a reward – typically cash, in-app currency or discounts. Building viral growth through personalized and targeted referrals helps scale the user base. Some apps also let high-referring users unlock special status or badges to encourage ongoing referrals.

Sponsorships: Approach brands, agencies, or other businesses to sponsor different parts of your app experience in return for promotions and branding. Common sponsorship opportunities include sponsored filters, featured app sections, login/launch page takeovers, exclusive offers etc. Analytics helps sponsors measure engagement with their promotions and campaigns. Sponsorships work best for apps with very large, loyal user communities.

Data monetization: For apps with access to valuable user data signals (demographics, behaviors, interests etc.), you can monetize anonymized insights through partnerships with market research firms, advertisers or other data buyers. It requires utmost responsibility and compliance with privacy regulations when handling personal user information.

Crowdfunding/Donations: Some passion apps rely on user goodwill and appeal to their communities for voluntary crowdfunding or micro-donations to continue development. While unpredictable, cultivated fanfare around new features or anniversary milestones can drive unprompted donations from loyal superfans.

Combining multiple monetization strategies often works best to maximize revenue potential and provide users flexibility in how they choose to engage and support an app over time. Testing new ideas is also key to continued growth and success with in-app monetization models. The right balance of different methods depends on the core app experience and business model.