Question: Can you recommend a service that allows me to add file upload capabilities to my app with a customizable interface?

If you need a service that lets you add file upload abilities to your app with a custom interface, Filestack is a great choice. It makes it easy to add file upload abilities to your apps with its customizable user interface and can handle uploads from local disk, cloud storage and device cameras. Filestack's feature-rich service includes virus, copyright, phishing, object and explicit content detection along with OCR abilities for data capture. It's great for apps that need to handle files in detail.

Another good option is Uploadcare, a full-featured file management service that lets you upload, process and deliver files in a lightweight, developer-friendly way. It offers features like real-time optimization, on-the-fly image processing, AI-powered image operations and automated document conversion. Uploadcare also offers secure delivery and access control with signed URLs, built-in security and malware filtering. Its customizable and scalable platform supports multiple JavaScript frameworks and APIs for custom integration, so it's a good option for a variety of use cases.

If you're looking for a service that's really focused on file processing, Transloadit could be the way to go. It lets you accept files from multiple sources, transcode them and deliver them fast through a Smart CDN. Transloadit supports a lot of programming languages and offers SDKs for several platforms. It's designed to automate media workflows and offer high uptime and scalability, so it's good for developers and businesses that need to handle files efficiently.

Also worth a look is Payload, a headless Content Management System (CMS) and application framework that can handle file upload processing among other things. Built with TypeScript and React, it offers AI-powered content generation, visual editing and custom component integration. Payload is flexible and extensible, so it's a good option for agencies, marketers and developers who want to build their own business solutions.