What file size limits exist for OnionShare?

OnionShare has no hard-coded file size limit. In practice, your internet connection's upload speed is the bottleneck. Transferring a 1GB file over a typical home internet upload speed (10-50 Mbit/s) takes 2-15 minutes. Tor adds overhead - effective throughput is typically 1-5 Mbit/s per circuit. For files larger than a few hundred MB, OnionShare becomes slow. Consider using SFTP over Tor for large file transfers where you have server infrastructure available.

How do recipients verify that a downloaded file has not been tampered with?

Provide a cryptographic hash (SHA-256) of the file through an independent channel (in an encrypted message, in a PGP-signed announcement). Recipients verify: sha256sum downloaded-file.ext and compare to the expected hash. For software distributions, provide a PGP signature of the file: gpg --detach-sign --armor software.tar.gz produces software.tar.gz.asc. Recipients verify with gpg --verify software.tar.gz.asc software.tar.gz. The verification step is important for sensitive files where tampering during transfer is a concern.

Can I use Tor Browser to upload files via a web form on a .onion service?

Yes. Tor Browser supports file uploads through standard HTML file input elements. Large file uploads (over a few hundred MB) may be slow due to Tor bandwidth limitations. For large uploads, use an SFTP client with Tor proxy instead of browser-based upload. Tor Browser does not support WebRTC-based file transfer (WebRTC is disabled in Tor Browser) so applications using WebRTC for peer-to-peer file transfer will not work.

What encryption is used for OnionShare file transfers?

OnionShare file transfers use Tor's built-in encryption for the transport layer (multiple layers of TLS encryption through Tor circuits). The file content itself is not additionally encrypted by OnionShare - the file is transmitted in plaintext over the encrypted Tor circuit. If you need the file to be encrypted even if the Tor circuit is somehow compromised, encrypt the file with PGP or AES (using gpg --symmetric or similar) before sharing via OnionShare.

Is there a difference between sharing with a specific recipient versus a public download?

Yes. OnionShare's private mode generates both a .onion address and an access key - the recipient needs both to download, preventing anyone who discovers the .onion address from downloading. For public downloads (like software releases), use OnionShare without private mode or use a self-hosted file server with autoindex. Private mode is appropriate for sensitive documents; public mode is appropriate for files you want to distribute widely.

Secure File Sharing on the Dark Web: Anonymous Transfer Methods

Sharing files anonymously requires both an anonymous transport layer (to hide who is sending to whom) and appropriate encryption (to hide what is being sent). Tor provides the anonymous transport layer; the choice of file transfer method determines the encryption model and operational complexity. Different use cases demand different approaches: sharing a single document with a specific recipient, operating a public download server for many anonymous users, or synchronizing files between multiple devices all require different tools. This guide compares the major approaches to file sharing over Tor, covering OnionShare (the simplest tool for direct file transfer), SFTP over Tor (for interactive file management), Tor-accessible cloud storage (for scalable distribution), and self-hosted .onion file servers.

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OnionShare: Simplest Direct File Transfer

OnionShare (onionshare.org) is a tool that creates a temporary or persistent .onion address for file sharing directly from your computer. No server required: your computer acts as the server while OnionShare is running. Usage: drag the file into OnionShare, click 'Start Sharing', share the generated .onion address with the recipient. The recipient opens the address in Tor Browser and downloads the file directly from your computer. After the download completes (or after a set number of downloads), OnionShare stops the server. OnionShare uses Tor's hidden service protocol so the recipient's IP is not revealed to you and your IP is not revealed to the recipient. OnionShare 2.6+ supports: private mode (recipient needs an access key in addition to the .onion address), persistent mode (the same .onion address works across multiple sessions), and receive mode (the other person can upload files to you). OnionShare is ideal for: sharing documents with sources, sending files to a single recipient without email, one-off anonymous file transfers. Not suitable for: high-bandwidth transfers (your home connection is the bottleneck), many simultaneous recipients.

SFTP over Tor Hidden Service

SFTP (SSH File Transfer Protocol) over a Tor hidden service provides interactive file management: upload, download, browse directories, and manage permissions from any SFTP client configured with a Tor proxy. Configure SSH as a Tor hidden service: HiddenServicePort 22 127.0.0.1:22 in torrc. Connect with an SFTP client using the SOCKS5 proxy: FileZilla -> Site Manager -> Protocol: SFTP, Host: youraddress.onion, Connection through proxy: SOCKS5 proxy 127.0.0.1:9050. Or use the command line: sftp -o ProxyCommand='ncat --proxy 127.0.0.1:9050 --proxy-type socks5 %h %p' user@youraddress.onion. SFTP over Tor is slower than direct SFTP due to Tor overhead but provides strong anonymity for both client and server. For large file transfers (gigabytes), the bandwidth limitation of Tor circuits may be frustrating - plan for slower transfer speeds (typically 1-10 Mbit/s per circuit).

Self-Hosted .onion File Server

For distributing files to many anonymous recipients, a self-hosted .onion file server provides scalable distribution. Simple setup with Nginx: configure Nginx with autoindex on; for a specific directory, create a virtual host for the hidden service port that serves the files directory with automatic file listing. Visitors see a directory listing and can download individual files. This is simple and suitable for distributing public files (documentation, software, media) to anonymous recipients. For access-controlled distribution (some files require authorization), add HTTP basic authentication or implement a simple token-based access control in the application layer. For very large file libraries, pair with BitTorrent: seed files on the clearnet, post magnet links on the .onion site, and provide a Tor-friendly way to download (Tor Browser cannot natively download torrents - provide direct HTTP download links alongside magnet links).

Encrypted Cloud Storage Accessible from Dark Web

Several encrypted cloud storage services are accessible via Tor: ProtonDrive (proton.me) is accessible from Tor Browser, CryptPad (self-hosted) can be deployed as a .onion service, and Nextcloud (self-hosted) with E2EE enables Tor-accessible encrypted cloud storage. For self-hosted solutions, Nextcloud deployed as a .onion hidden service provides: file storage, sharing links (generate a link to a specific file that expires after a set number of downloads or time period), collaborative editing (Nextcloud Office), and multi-device sync (Nextcloud clients support SOCKS5 proxy for Tor routing). Nextcloud's sharing links work well for distributing files anonymously: generate a link with download limit and expiry, share via encrypted channel, recipient downloads through Tor Browser.

Choosing the Right File Sharing Method

Decision guide for dark web file sharing: OnionShare - best for one-time transfers between two parties, no infrastructure needed, simple to use, but requires the sender's computer to be online during transfer. SFTP over Tor hidden service - best for ongoing access to a file server by authorized users, interactive file management, requires server infrastructure. Self-hosted .onion file server - best for distributing files to many anonymous recipients, scalable, requires server infrastructure and maintenance. Encrypted cloud (.onion Nextcloud) - best for team file sharing with multiple authorized users, persistent storage, requires more complex setup. For journalists sharing documents with editors: OnionShare or SFTP. For software developers distributing anonymized builds: self-hosted file server. For research teams sharing datasets: Nextcloud with E2EE. For one-time sensitive document delivery: OnionShare.

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