The Complete OBS Setup Guide for Multistreaming

You need three things before touching OBS’s settings: a CastFork account, a stream card set up for the encoder path (Home → New Stream → Encoder), and your ingest URL and stream key, which live in that card’s Stream Settings panel once your email is verified.

Your ingest URL looks like rtmp://ingest.castfork.com/live, and your stream key is a long, unique string starting with cf_live_. Both stay the same across sessions unless you reset the key, so you only paste them into OBS once.

1. Open OBS and go to Settings → Stream.
2. Set Service to Custom.
3. Paste rtmp://ingest.castfork.com/live into the Server field.
4. Paste your stream key into the Stream Key field.
5. Click Apply, then OK.

That’s the entire connection step. OBS doesn’t need to know which platforms you’re actually going to — that decision happens on the CastFork side, by toggling destinations on the stream card. One encoder configuration serves every combination of destinations you’ll ever use.

x264 (OBS’s software encoder) generally produces the best quality per bit, but it competes for the same CPU your game, browser sources, or other software are using. A hardware encoder — NVENC on NVIDIA GPUs, AMF on AMD, Quick Sync on Intel — offloads that work to dedicated hardware on the graphics card or processor, at a small quality cost per bit compared to x264. For a single OBS instance feeding CastFork’s fan-out, a hardware encoder is usually the practical choice: you’re not running four copies of OBS the way a DIY multistreaming setup would need, but you’re often still doing something else demanding (gaming, screen capture, a second app) at the same time.

Under Settings → Output, switch the output mode to Advanced so you get direct control over encoder, bitrate, and rate control:

• Encoder: x264 (CPU) if your machine can handle it at your target bitrate, or a hardware encoder (NVENC, AMF, Quick Sync) if you're also running a game or other CPU-heavy software alongside OBS.
• Rate control: CBR (constant bitrate) — variable bitrate can spike above what your upload can sustain and cause drops.
• Bitrate: match what your connection and resolution can actually support — see the bitrate section below.
• Keyframe interval: 2 seconds. This is the value CastFork and most destination platforms expect; a mismatched keyframe interval is a common, hard-to-diagnose cause of quality drops on some platforms.
• Audio: 128 kbps, 48 kHz, stereo AAC. That matches CastFork Studio's own program audio spec, so anything you compare against sounds consistent.

Don’t guess this part. Run a real upload speed test (fast.com or similar — your download speed tells you nothing about upload), then use the bitrate calculator with your resolution, framerate, and codec to get a recommended band and an honest headroom verdict. As a rule of thumb, your upload speed should sit at roughly 1.5x your total stream bitrate (video plus the 128 kbps of audio) so there’s room left for network jitter and anything else sharing your connection. Passthrough ingest on CastFork supports up to 4K/2160p on every plan, but there’s no point setting a resolution and bitrate your upload can’t actually sustain — that’s what produces dropped frames, not a settings problem on our end.

Click Start Streaming in OBS once your settings are saved. Your CastFork dashboard should show the stream card go live within a few seconds — that confirms the RTMP handshake worked and OBS is actually pushing frames, before you toggle a single destination on. If nothing shows up as connected within about 10 seconds:

• Re-check the server URL for typos — a stray character in rtmp://ingest.castfork.com/live is the single most common cause.
• Re-copy the stream key rather than retyping it; these are long, random strings and easy to mistype by hand.
• Confirm your account's email is verified — ingest credentials don't activate until it is.
• Check your firewall isn't blocking outbound traffic on port 1935, the standard RTMP port.

Once the connection itself is solid, toggle on one low-stakes destination — an unlisted YouTube stream works well for this — and confirm picture and audio look right there too before enabling everything you actually intend to go live to.

None of the ingest configuration above touches your Scenes or Sources in OBS — that part of the setup is entirely yours, the same as streaming to a single platform. What’s worth doing once, before a real broadcast: build a simple "Starting Soon" scene with a static graphic or the countdown page embedded as a browser source, so the first thing viewers on any destination see isn’t a bare camera feed while you’re still getting comfortable. Switching scenes doesn’t touch your RTMP connection at all — the stream stays live the entire time you’re changing what’s actually on screen.

Once OBS is pointed at your ingest URL and key, you never touch those settings again for a normal stream. Save the profile in OBS once everything above is dialed in, so a fresh install or a machine change is a five-minute restore instead of redoing every step from scratch. Every future broadcast is the same OBS profile, with whatever destinations you want enabled for that particular stream — see how the destination toggles work — and Free covers two destinations at once with no time limit, so there’s no reason to put this off until you’re on a paid plan. Compare plans once you know how many destinations you actually want live together.