StreamLive Pro

RTMP vs RTMPS vs SRT: which one to use and when

RTMP vs RTMPS vs SRT compared: transport, ports, encryption, how each handles a bad line, which networks accept which, and how to choose for your encoder.

Updated November 5, 2026 · 5 min read

RTMP, RTMPS and SRT all carry a live stream from your encoder to a server. RTMP is the old default that everything supports. RTMPS is the same thing inside encryption, on a port that almost no network blocks. SRT is built for unreliable lines and recovers lost packets better, at the cost of a little delay and a little more setup. Where to find keys on each network, and RTSP and WHIP, are in RTMP and stream keys: where to find them, what breaks; this page is the side-by-side comparison and the decision.

Short definitions

RTMP (Real-Time Messaging Protocol). Pushes video over TCP, usually to port 1935. TCP resends every lost packet in order, which is reliable on a clean line and stalls on a lossy one. Not encrypted: the stream key travels in the clear.

RTMPS. RTMP inside TLS, the encryption used by HTTPS, usually on port 443. Same behaviour on a bad line as RTMP, but the key cannot be read on the way, and corporate or venue firewalls that block 1935 normally let 443 through.

SRT (Secure Reliable Transport). Pushes video over UDP and resends lost packets only within a time window you set (latency). Optional AES encryption with a passphrase; vMix, for example, offers up to 256-bit (vMix: SRT). Has three connection modes: Caller, Listener and Rendezvous.

Side by side

Sources for the last row: YouTube's encoder page lists RTMP and RTMPS (YouTube Help: live encoder settings); Meta's Live Video API returns an RTMPS ingest address (Meta: Live Video API, getting started); Instagram's stream URL for computer lives starts with rtmps://. All checked 5 November 2026.

What a bad line does to each

Take an example: the Wi-Fi in a hall loses a small share of packets for ten seconds while people arrive.

• RTMP and RTMPS. TCP holds back everything that comes after a lost packet until that packet arrives again. The encoder's buffer fills, OBS starts counting dropped frames, and if the loss goes on long enough the connection resets and the encoder reconnects. Viewers see a freeze, sometimes a short break.
• SRT. The receiver asks again for the missing packets and keeps playing what it has. If the resent packets arrive inside the latency window, nothing is visible. If they arrive too late, viewers see a short glitch, but the connection stays up.

That is the whole case for SRT: it trades a fixed, small delay for resilience. On a clean wired line there is nothing to recover, and the extra setup buys nothing.

Ports and firewalls

• RTMP usually needs outgoing TCP port 1935. Office, school and hotel networks often block it.
• RTMPS uses TCP port 443, the same port as every secure web page, so it passes almost anywhere a browser works.
• SRT uses UDP on a port set by the receiving server. Some guest and corporate networks block outgoing UDP. Test at the venue before the day, and keep the RTMPS address as a fallback.

Encryption and your stream key

With plain RTMP the stream key travels unencrypted. On a shared network, someone watching the traffic could read it and broadcast on your channel. RTMPS wraps the whole connection, key included, in TLS. SRT encrypts the stream with the passphrase, and a push without the right passphrase is refused. Whatever the protocol, treat the key and the passphrase as passwords and never show them on screen.

WHIP, the fourth tab

WHIP sends video over WebRTC, the technology behind video calls, and aims for very low delay. Encoder support is newer: recent OBS versions have it, many tools do not. In StreamLive Pro, WHIP is a beta tab on the Encoder card for the incoming stream only; it is not offered as a destination.

Which one to choose

• Office, school or venue network: RTMPS. Port 443 is almost always open.
• Home or studio on a cable, stable line: RTMPS, or RTMP if your encoder has no RTMPS.
• Mobile data, shared Wi-Fi, long distance: SRT, with latency set to a few times the round trip (OBS says at least 2.5 times, vMix at least 4 times the ping).
• The line is simply too slow for the bitrate: none of them fixes that. Lower the bitrate (Upload speed and bitrate for multistreaming).

Common mistakes

• Choosing SRT to fix a slow line. SRT recovers lost packets; it does not add bandwidth. Lower the bitrate instead.
• SRT in Listener mode. Pushing to a relay needs Caller mode.
• Plain RTMP on public Wi-Fi. The key travels in the clear. Use RTMPS.
• An rtmp:// address pasted into an SRT setting, or the reverse. Each tab on the Encoder card has its own address. Copy from the tab that matches the protocol you set in the encoder.

Where they appear in StreamLive Pro

• Coming in, from your encoder. The Encoder card has RTMP, RTMPS, SRT and WHIP (beta) tabs. RTMP and RTMPS show an address and a separate key; SRT shows an address and, when the broadcast has one, a separate passphrase. Encoder ingest is on the paid plans. Setup: Connect OBS to StreamLive Pro and multistream and Stream with SRT from OBS, vMix or a hardware encoder.
• Going out, to the networks. Our servers push each destination over RTMP, RTMPS or SRT, whichever that destination uses. Your choice for the incoming leg does not change what YouTube or Facebook receive.
• Your own servers. A custom destination accepts addresses starting with rtmp://, rtmps:// or srt://. WHIP and HLS destinations are not supported. See Stream to a custom RTMP or SRT server.

Frequently asked questions

What is the main difference between RTMP and SRT?

RTMP runs over TCP and stalls while it resends lost data. SRT runs over UDP and recovers lost packets within a latency window you set, so it holds up better on mobile, Wi-Fi and long routes.

Is RTMPS better than RTMP?

For most people, yes. It carries the same stream but encrypted, so the key cannot be read on the way, and it usually runs on port 443, which networks rarely block.

Does YouTube accept SRT?

YouTube's encoder settings page lists RTMP and RTMPS for ingest. To use SRT from your encoder, send it to a relay such as StreamLive Pro, which delivers to YouTube in a protocol YouTube accepts.

Can I switch protocol from one broadcast to the next?

Yes. The Encoder card shows an RTMP, an RTMPS and an SRT address for the same broadcast. Pick the tab that suits the network you are on and set your encoder to match.

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