FileUpload

FileUpload refers to the process of sending files from a client to a server or storage system over a network. It is a common feature in web and mobile applications, typically implemented using HTTP POST requests with multipart/form-data, and supports single or multiple files per submission.

In HTTP multipart/form-data, the browser or client packages files into one or more parts, each with its own headers (such as Content-Disposition and Content-Type) followed by the binary content. Server-side frameworks parse the request and expose uploaded files as objects containing metadata (name, size, MIME type) and a temporary storage location. Some platforms also support streaming or chunked uploads to handle large files or unstable connections.

After receipt, the application validates the files and then stores them to disk, a database, or cloud storage. Validation commonly covers size limits, allowed MIME types or extensions, and content checks. Best practices include generating new, non-guessable filenames, storing files outside the web root, and applying access controls and lifecycle policies.

Security considerations are central to file uploads. Risks include malware, resource exhaustion, and the execution of uploaded content. Mitigations include strict size limits, whitelisting of extensions and MIME types, antivirus or content scanning, not exposing uploads via direct execution, and enforcing authentication, authorization, and rate limiting.

Client-side and APIs: Users typically interact with a file input control or drag-and-drop interfaces. Progress indicators and resumable uploads may be implemented with client-side libraries, using techniques such as chunked transfers or specialized protocols to recover from interruptions, and often leveraging direct-to-storage uploads to reduce server load.