Brian from Backblaze here.
> Range header has existed since HTTP 1.1
Backblaze built the original zip restore functionality in 2007 and I believe the range header was introduced after that? We FULLY support the range header in our B2 Object Storage and we actually have support for it (now) in the ZIP file download functionality.
However, because we built the client side custom program bzdownloader (our restartable restore downloader) it seems to still succeed in some situations where a web browser doesn't succeed. We can slowly retire our custom bzdownloader application as all web browsers catch up and have restartable downloads.