UploadThing File Upload Service

UploadThing is a file upload service that provides type-safe file upload endpoints, storage, and delivery for full-stack TypeScript applications without requiring developers to configure S3 buckets, presigned URLs, CORS policies, or backend upload handlers manually. The integration model uses a server-side file router definition where each upload route specifies the allowed MIME types, maximum file size, and a callback function that receives the uploaded file metadata and authenticated user context. On the client side, React and Solid hooks expose typed upload functions, drag-and-drop file input components, and progress tracking, so the entire upload flow from file selection through storage completion is handled by the library. Files are stored in regional data centers with global CDN delivery, and the platform handles virus scanning, image optimization, content-type validation, and rate limiting automatically. The file router approach means access control is enforced at the route definition level: the callback function can check the user identity, verify plan limits, and conditionally allow or reject the upload before any bytes are transferred. A presigned URL flow is also available for direct-to-S3 uploads where the application does not want to proxy file data through its own servers. The platform supports multipart uploads for files up to several gigabytes, batch uploads for multiple files in a single operation, webhooks for post-upload processing, and signed URLs for time-limited access to private files. Integration packages are available for Next.js, Remix, Astro, SvelteKit, Nuxt, Hono, and Express, each providing framework-native middleware and route handlers.