Technical

Will QUIC Replace TCP for MTProto? (2026 Status)

TCP has been the default transport for MTProto since day one. QUIC is faster but has trade-offs. Here is where things stand.

TGFast Editorial Team

MTProto Proxy Engineers · Censorship Circumvention Researchers

Published April 27, 2026 Updated May 15, 2026 8 min read 327 words

Why this matters

TCP is what makes MTProto reliable, but it has well-known downsides: head-of-line blocking, slow connection setup, and a single congestion control loop per connection. QUIC, the protocol behind HTTP/3, addresses all three. Telegram experimented with QUIC for MTProto in 2023-2024 but has not (as of early 2026) made it the default. Why?

QUIC advantages

For Telegram's workload, QUIC offers: 0-RTT connection setup (faster app launch); independent stream multiplexing (a slow file upload does not block chat sync); better mobility (a connection survives changing networks). All of these would make Telegram feel snappier on mobile.

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QUIC disadvantages

QUIC runs over UDP. Many enterprise firewalls and ISPs deprioritise or rate-limit UDP traffic. UDP is also more aggressively blocked in censored regions because it is associated with VPN protocols. In Iran specifically, UDP-based protocols have a much shorter survival window than TCP-based ones.

Telegram's pragmatic stance

Telegram's engineering team has stated they prefer to maintain TCP-based MTProto as the universal baseline because it works everywhere, while opportunistically using QUIC where the network allows. As of 2026, Telegram's desktop client uses QUIC by default for users in non-restricted regions and falls back to TCP automatically when QUIC fails.

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What this means for proxies

TGFast servers currently support TCP only. We have evaluated adding QUIC support but concluded that for our user base — heavily concentrated in restricted regions — TCP gives more reliable performance. We will reconsider when QUIC blocking becomes less common in Iran and China.

How to test QUIC manually

Telegram Desktop has a hidden setting to force QUIC: launch with the flag --use-quic (Linux/Mac) or %path-to-telegram%\Telegram.exe -use-quic on Windows. If your network supports it, you should see a small latency improvement on chat load.

Future direction

We expect QUIC adoption to grow over the next 2-3 years as ISPs catch up. By 2028, QUIC may be the default for MTProto. TGFast will follow Telegram's lead and add QUIC proxy support when the upstream protocol stabilises.

Frequently Asked Questions

How is MTProto different from SOCKS5 or Shadowsocks?

MTProto is Telegram's native protocol, so traffic looks indistinguishable from a normal Telegram connection to deep packet inspection. SOCKS5 is a generic proxy with a recognizable handshake; Shadowsocks adds obfuscation but still requires the operator to defend their port and keys against probing. MTProto with Fake-TLS adds a TLS-1.3-mimicking handshake that has proven the hardest of the three to fingerprint.

Why does the secret start with "dd" or "ee"?

The leading byte is a magic prefix that tells the Telegram client which obfuscation mode to negotiate. "dd" enables MTProto 2.0 random padding to defeat traffic analysis; "ee" indicates Fake-TLS mode where the entire session is wrapped in a TLS 1.3 handshake. Both are interoperable with all modern Telegram clients.

Can a network operator detect that I am using an MTProto proxy?

A determined operator can sometimes flag suspicious flows by timing analysis, but the encrypted payload itself is opaque. Fake-TLS makes detection significantly harder because the handshake mimics a real HTTPS site (including SNI, ALPN and certificate exchange). Even when flagged, blocking is per-IP, not per-protocol — which is why TGFast rotates IPs continuously.

Does an MTProto proxy add real cryptography or only obfuscation?

Both. The MTProto 2.0 transport adds AES-256-IGE encryption between client and server with per-session keys derived from the shared secret, and Fake-TLS wraps that channel inside a real TLS 1.3 handshake. Even if the proxy operator were malicious, they could not decrypt the inner Telegram session — that key is negotiated end-to-end with Telegram's data centres.

How does TGFast pick which servers to deploy and where?

We monitor latency and packet loss from probe nodes in 14 cities across the regions hit hardest by Telegram restrictions. New servers are spun up where the median latency to nearby ISPs falls below 80 ms and where the upstream provider has historically resisted ISP take-down requests. Capacity is rebalanced weekly.