obfs4 vs. WebTunnel: Tor Bridge Transport Comparison 2026

obfs4 (obfuscated transport protocol version 4) has been the primary Tor bridge transport since its development by David Fifield. It transforms Tor's traffic signature into traffic that appears as random bytes, without distinctive packet sizes or timing patterns that DPI can identify as Tor. obfs4 is well-tested in production across China, Iran, Russia, and other censored environments. Its main limitation is that sufficiently advanced DPI can still identify obfs4 traffic through statistical analysis of traffic patterns, even if it cannot read the content. China's Great Firewall has become increasingly effective at detecting obfs4 in recent years.

WebTunnel is a newer pluggable transport that wraps Tor traffic inside WebSocket connections that appear as standard HTTPS traffic to the same website. The bridge's server presents a legitimate website at its IP address, so when censors probe it (active probing), they receive a real website response. The Tor traffic tunneled through WebSocket blends with actual web traffic patterns. WebTunnel requires: a domain name, a TLS certificate for that domain, and a decoy website (can be a simple static site) served on the same server. This additional infrastructure requirement is higher than obfs4 but provides meaningfully better blocking resistance in environments with advanced DPI.

obfs4 blocking resistance: good against passive DPI based on traffic signatures; vulnerable to active probing (a censor probing an obfs4 bridge IP sees clearly that it is running obfs4 if they send probe traffic). WebTunnel blocking resistance: excellent against passive DPI (traffic is indistinguishable from HTTPS browsing); excellent against active probing (probes receive legitimate website content). WebTunnel's active probing resistance is its key advantage. China's GFW uses active probing extensively, making WebTunnel significantly harder to block than obfs4. For Iran's filtering systems, both provide reasonable resistance with WebTunnel having an edge for sophisticated censors.

obfs4 setup: install Tor, add Bridge, ServerTransportPlugin, and ExtORPort lines to torrc. No additional infrastructure required. Can run on any IP address without a domain. WebTunnel setup: requires a domain name, TLS certificate (Let's Encrypt), a decoy website (simple nginx serving static content), Tor and obfs4proxy configured with the WebTunnel transport, and proper TLS configuration. Approximately 2-3x more setup effort than obfs4. The additional infrastructure cost (domain + TLS + decoy site) is relatively modest but creates ongoing maintenance requirements.

Run both transports if possible - they serve different censorship environments. For Romania VPS operators: configure both obfs4 and WebTunnel, distributing addresses for both to users. obfs4 works for users in moderate-censorship environments (Turkey, some ISPs in Russia). WebTunnel is needed for users in advanced-censorship environments (China, during high-enforcement periods in Iran). If forced to choose one: WebTunnel provides forward-looking blocking resistance as censors increasingly adopt active probing. If running only one and infrastructure is constrained: obfs4 for simplicity. Submit both transport types to BridgeDB to serve the full range of censored users.