Send Folders Online Without Zipping: Direct Browser Directory Traversal

The Friction of Zipping Folders

For decades, zipping folders has been the standard way to share directories online. Whether sending a collection of design assets, a software codebase, or a music project, users compress folders into .zip or .tar archives before uploading. This process introduces several issues: it requires extra disk space, consumes CPU cycles, and adds time to the transfer. On mobile devices, zipping and unzipping folders can be particularly difficult due to limited file management systems. Our platform resolves this by allowing you to transfer entire folders directly through the browser without zipping.

By leveraging the HTML5 File System Access API, our platform reads directory structures directly from your local drive. When you drag and drop a folder into the transfer area, the browser recursively reads its files and folder structure. This metadata is sent to the receiver, allowing the system to reconstruct the exact directory tree on their device in real-time, providing a seamless sharing experience.

This method saves time and disk space. You do not need to wait for a 10GB folder to compress before sending, nor does the recipient have to wait to extract it. Files transfer instantly, and the folder structure is maintained automatically, simplifying your workflow.

How Browser Directory Reader Works

The ability to transfer folders without zipping relies on the HTML5 DirectoryReader interface. When a user selects a folder, the browser creates a file system handle. The application then recursively queries this handle to build a complete manifest of all files, subfolders, and relative paths. This map is shared with the receiving peer, establishing the structure before the transfer begins.

Once the folder structure is mapped, the sender's browser reads each file as a binary stream. These streams are divided into small chunks and sent over WebRTC data channels. At the receiving end, the browser uses the mapped structure to write each file block back to its correct location. This process ensures that files are reconstructed in their original directories without requiring compression, providing an efficient way to transfer folders.

Furthermore, because the transfer is direct and serverless, there are no file count or folder depth limitations. You can send nested folders containing thousands of individual files, such as build directories or photo archives, without worrying about compression errors or server timeouts.

Reconstructing Folders on the Fly

As file chunks travel across the WebRTC connection, the receiving browser uses stream writing interfaces to reconstruct the folder structure on the fly. In modern browsers, this is handled by the File System Access API, which allows web applications to write data directly to the user's local disk after receiving permission. This interface permits the browser to create directories and write files directly, matching the sender's folder structure.

If the browser does not support direct disk writing (such as on certain mobile platforms), the system buffers the files in memory and packages them into a download stream. While this fallback is available, most desktop browsers support direct writing, providing a seamless folder transfer experience that maintains your directory structure without requiring manual zipping.

Security and Privacy of Directory Metadata

When sharing folders, privacy is a key concern. Traditional cloud services scan uploaded zip archives, which can expose your file names and folder structures. Our platform uses end-to-end encryption to protect this metadata. The folder structure map is encrypted in the sender's browser using AES-256-GCM before transmission. This ensures that directory names, file structures, and metadata are protected from third-party interception during the transfer.

Frequently Asked Questions on Folder Sharing