To build a pet food delivery app, start by identifying your target audience and their needs. Design a user-friendly interface that allows easy navigation and ordering. Include features like product categories, detailed descriptions, and customer reviews. Implement a secure payment gateway for smooth transactions. Offer subscription options for regular deliveries and promotions to encourage loyalty. Partner with local suppliers to ensure a variety of high-quality products. Incorporate real-time order tracking and notifications to keep customers informed. Finally, devise a marketing strategy that utilizes social media and pet communities to attract users and boost engagement with your app.