Uploads transfer a local file into a running remote browser. Downloads expose files produced by that session. They are different from browser profile contexts.
Uploads are limited to 512 KiB per file and 16 files per running session and are removed when the session ends. The Cloudflare Containers transport currently refuses uploads and downloads.
Downloads use application-authenticated metadata and byte streams. Transport, storage, retention and quota availability determine whether a file can be retained after browser shutdown. No signed public download URL is issued. Screenshots and PDFs can be produced over CDP.