active-storage

Secure file uploads in Rails 8 are handled using Active Storage to attach files to models via has_one_attached and has_many_attached, with built-in content-type and size validations to prevent unsafe uploads.

Yes, direct browser uploads are supported for large files across local and cloud storage backends like S3 or GCS, allowing files to upload directly to the storage service without passing through your application servers.

The best way to generate image variants is using Active Storage's lazy variant processing, which creates versions on-demand, supports optional background processing, and uses Rails-friendly eager loading to prevent N+1 queries.

You validate content types, file sizes, and filenames for Active Storage attachments by applying built-in validation rules to your models, ensuring that only safe and appropriately sized files are accepted into your database.