Managing files across cloud storage providers usually means juggling a handful of different tools — a desktop client for S3, a web console for another bucket, maybe a WebDAV app for a self-hosted server. Cumulus takes a simpler approach: it puts a full-featured file manager directly inside your browser as a Chrome extension, with no separate app to install and no server in between.
At its core, Cumulus speaks the protocols that matter: Cloudflare R2, Amazon S3, Backblaze B2, Google Cloud Storage, Wasabi, DigitalOcean Spaces, MinIO, any other S3-compatible storage, and WebDAV. Multiple servers can be saved side by side, each with its own credentials, and switching between them takes a single click — the same workflow long-time FileZilla users will recognize from its Site Manager.
The day-to-day basics are all covered: drag-and-drop uploads with up to 50 parallel transfers, downloads that preserve folder structure, inline renaming, recursive folder deletion, and instant search and sorting. A batch rename engine lets you stack rules — find-and-replace with regex, auto-numbering, case conversion, timestamps — and preview the result before committing. Files and folders can be copied or moved between directories with a clipboard-style workflow, complete with conflict handling when names collide. A grid view with lazy-loaded thumbnails sits alongside the classic list view for browsing image and video collections.
What sets Cumulus apart structurally is what it doesn't do: there's no backend server, no SDK, no telemetry, and no build step. It's pure JavaScript talking directly to your storage provider, signing requests with AWS Signature V4 via the browser's native WebCrypto API. Every saved credential is encrypted with AES-256-GCM before it touches local storage, so the only parties who ever see your keys are you and your cloud provider.
The result is a tool that feels closer to a native desktop client than a typical browser extension, while staying entirely within the browser sandbox — open source, auditable, and free of any middleman between you and your data.
Install on chrome :
https://chromewebstore.google.com/detail/cumulus-%E2%80%94-s3-r2-webdav-fi/bcljbdjgihdnccbablncpdhankediple
