Simulcasting live video to multiple platforms

You go live.

And half your audience isn’t there.

Some are on YouTube. Others swear by Twitch. A few still hang out on Facebook Live.

So what do you do? Pick one and hope for the best? Or melt your upstream bandwidth trying to push to all of them at once?

Local encoders hate this game. Multiple RTMP connections chew up CPU, hog bandwidth, and introduce just enough chaos that something will fail mid-stream.

And yet, if you’re serious about reach, you can’t ignore where your audience already is.

The question is: how do you get one live stream everywhere at once… without your gear waving the white flag?

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What is simulcasting?

Simulcasting, short for simultaneous broadcasting, is the process of taking a single live video feed and delivering it to multiple destinations at the same time.

In streaming architecture terms, it’s a single-ingest, multi-output workflow. Your encoder (OBS, Wirecast, vMix, hardware appliance, etc.) sends one upstream feed, typically via RTMP or SRT to an ingest endpoint. That ingest point then fans out the stream to multiple platforms, each with their own quirks:

• YouTube Live wants RTMP, capped at 51 Mbps. ‍
• Twitch has a strict max bitrate and resolution policy. ‍
• Facebook Live requires periodic stream key refreshes and has a max stream duration. ‍
• LinkedIn Live enforces strict ingest URL formats and authentication.

Without simulcasting, your encoder has to connect to each platform directly, one RTMP session for YouTube, another for Twitch, another for Facebook, and so on. Each connection is its own upload.

That means your outbound bandwidth usage, CPU load, and encoder stress scale with every new destination. On a 10 Mbps upstream, trying to push three separate 1080p streams is just asking for dropped frames, rising latency, and a fan that sounds like it’s about to take off.

With simulcasting, you only send one master stream, usually at the highest bitrate and resolution you want any platform to get,  to a replication service or media server in the cloud. From there, the cloud handles all the messy parts:

• Protocol conversion  e.g., RTMP ingest → HLS out, or RTMP → multiple RTMP outputs. ‍
• Bitrate ladder adjustments so each destination gets a format it can accept. ‍
• Stream key injection per platform so you don’t have to juggle them locally. ‍
• Failover and retries if a platform drops mid-stream.

The result is simple:

• One high-quality upstream from your location.
• Multiple optimized outputs for each platform, handled off-site.
• No more building and maintaining a separate workflow for every audience.

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Why simulcasting is worth it?

If you’re already running a live stream, you might as well make the most of it. Simulcasting means you get more reach, more engagement, and more chances to be found, with almost zero extra effort on your end. Here’s why it’s become a no-brainer for most teams:

• Reach every audience, everywhere
  Every platform’s got its own user base. Gamers on Twitch, communities on Facebook, creators on YouTube. Simulcasting means you don’t force people to jump platforms, your stream just shows up where they’re already watching.
  

• Real-time interaction, no silos
  Nobody wants to manage five chats at once, but simulcasting makes it doable. Respond to YouTube comments and Twitch reactions in real time, all from a single workflow. Your viewers feel seen, not ignored.
  

• Algorithm-proof discoverability
  No one trusts a platform algorithm. Simulcasting gives you more surface area: if one platform buries you, another might pick you up. The more engines working for you, the better your odds of being found.
  

• Single workflow, less overhead
  Running separate encoders for every destination is a waste of time (and bandwidth). With simulcasting, you push one stream and the infra takes care of fan-out. Fewer moving parts, fewer headaches.

Now, you could duct-tape your own simulcasting setups, spin up extra servers, configure custom RTMP outputs, troubleshoot every time a platform changes its ingest URL. Plenty of devs have gone down that road. Most don’t do it twice.

Or you could let FastPix handle it. The idea: you send one stream in, and we worry about getting it everywhere it needs to go. No more context switching, no more guessing which output is actually live.

Here’s how it works in practice.

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How to simulcast with FastPix

So you want to reach everyone at once, without the pain of managing three (or more) different streaming setups. FastPix makes that about as simple as it gets. Whether your crowd is on Twitch, YouTube, Facebook, or somewhere new, you can push one stream and let the platform handle the fan-out.

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Here’s how to get simulcasting up and running with FastPix:

1. Spin up a live stream

Start by creating a live stream using the FastPix Create Livestream API. You’ll get back a stream ID and a stream key, think of these as your unique handles for everything that comes next. They’re what connect your live source to FastPix and, from there, out to the world.

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2. Add your simulcast targets

This is where you tell FastPix where to send your stream. For each platform (Twitch, YouTube, Facebook, add as many as you need), you’ll use the FastPix Create Simulcast API. Just provide:

• Your stream ID

• The platform’s RTMP server URL (for Twitch: rtmp://hyd01.contribute.live-video.net/app/, for YouTube: rtmp://a.rtmp.youtube.com/live2, for Facebook: rtmp://live-api-s.facebook.com:80/rtmp/)

• Your stream key from that platform

Do this once per platform. Now, when you go live, FastPix will handle pushing your stream to all destinations in parallel.

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3. Wire up OBS (or your encoder of choice)

Open OBS and head to Settings → Stream. Select “Custom” as the service, and drop in your FastPix server URL: rtmps://live.fastpix.io:443/live

Paste your FastPix stream key.

That’s it, hit “Start Streaming” in OBS. FastPix will pick up your feed and fan it out to Twitch, YouTube, Facebook, or wherever else you’ve set up simulcast targets. No more copy-pasting to three dashboards. No “wait, did I update the right stream key?” moments.

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Creating a livestream with the FastPix dashboard

1. If you're new to FastPix, start by signing up at  https://dashboard.fastpix.io. After signing in, you'll be redirected to the main dashboard.

2. On the dashboard, hover over the left-hand menu and select "Live" to access the Live page.

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3. Now to create a new livestream, click the "Create live stream" button.

Note: Initially, you'll only be able to create test streams while on the trial plan.

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Upgrading to the pro plan

1. Go to your account settings, located in the bottom-left corner of the dashboard.

2. Select the "Billing and Payment" section to view available plans and click the "Upgrade" option.

3. Provide your payment details and any required information. Once the card is added, your Pro plan will be activated, granting you full access to all FastPix features.

Note: FastPix uses a usage-based pricing model. For more details, see pricing in detail.

Now as pro plan is activated. click on "Run Request" to create your livestream. To view your stream, click on "View Stream," which will take you to the Live Stream Details page.

Now that you have the streamId, you can use it to create multiple simulcast targets, such as Facebook, Twitch, and YouTube, by using the Simulcast API. Follow the same steps you used during the initial simulcast creation process with the API.

Use the stream key along with the FastPix RTMP URL: rtmps://live.fastpix.io:443/live‍

Apply the same OBS settings we discussed earlier, and then start streaming.  

In Twitch:

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In Facebook:

In YouTube:

You can even view the livestream in FastPix dashboard in the livestream detail page.

This streamlined process not only saves you time but also allows you to engage with a diverse audience across different platforms simultaneously.

By following these steps, you can maximize your reach and connect with viewers on multiple platforms with ease!

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The real challenges of simulcasting (and how to avoid the pain)

1. Stream sync issues: It’s surprisingly easy to end up with your stream running 10 seconds ahead on Twitch while lagging on YouTube. For real-time Q&A or community chat, that kills the moment. FastPix lines up your output across all platforms, so everyone’s watching the same moment together, no awkward time drift, just synchronized delivery everywhere.
   

2. Every platform has its own “special” rules: YouTube expects one flavor of RTMP, Facebook wants a different key, Twitch changes its ingest rules every few months. You end up trawling docs and fighting arcane error codes, sometimes mid-event. FastPix takes care of those config changes and API quirks for you; you stream to FastPix once, and it keeps your output up to date everywhere, even as platform specs shift.
   

3. Bandwidth overload: Try to simulcast the old-school way and your local network buckles under the load. Suddenly, your stream drops frames or quality tanks for everyone. With FastPix, you only send your video once. We handle all outbound traffic in the cloud, so your upload doesn’t become the bottleneck and your stream holds steady.
   

4. Error handling turns into a fire drill: When something fails (and it will, eventually), a dropped connection to one platform can mean downtime for all. Fixing it often means frantic reconnections and manual restarts. FastPix auto-detects drops and failures, quietly retrying in the background, so most issues are fixed before your audience even notices, and your stream stays up everywhere else.
   

5. Bitrate and quality headaches: Adaptive streaming is essential, but not every platform agrees on what “adaptive” means. Setting up custom ladders for each is tedious and full of edge cases. FastPix generates the right adaptive ladders and stream variants for every target automatically. You get smooth playback and optimal quality on every platform, without hand-tuning.
   

6. Metadata becomes a mess: You tweak your title or description for one platform and forget to update the rest, now viewers are confused or missing crucial info. With FastPix, you edit once and your metadata is synced everywhere. Titles, captions, and descriptions are always consistent, right where they need to be.

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Simulcasting vs. Multicasting: What’s the real difference?

These two terms sound similar, but in streaming, they’re built for different jobs. Understanding the distinction can save a lot of bandwidth, configuration time, and head-scratching down the road.

Simulcasting is your go-to when you want to broadcast a live stream to multiple public platforms at once, YouTube, Twitch, Facebook, and more. Each service gets its own stream, so you’re sending out a separate signal for every destination. It’s a bit like hosting a radio show on multiple stations at the same time, maximum visibility, but your connection has to handle the extra traffic.

Multicasting, meanwhile, is designed for efficient streaming within a closed network like a company, campus, or controlled IPTV setup. Instead of sending a new copy of your stream to every viewer, multicasting uses specialized network protocols (think UDP and IGMP) to deliver a single stream that many devices can access at once. It’s ideal for big audiences on a private network, with minimal bandwidth overhead.

Technically, simulcasting means building integrations for each public platform and managing multiple outgoing streams, which can stretch your bandwidth. Multicasting requires a network that’s set up for multicast, but makes large-scale internal streaming far more efficient.

In short:
Simulcasting is built for broad public reach, great for creators, events, or any time your audience is scattered across the internet. Multicasting is about delivering a single stream to lots of people inside a network, perfect for private events or enterprise broadcasts. Choose the approach that matches your audience and your goals.

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Final words

You’ve got your stream, your story, your audience. Getting it everywhere? That’s its own challenge. FastPix takes care of the heavy lifting, simulcasting to every major platform, managing the bandwidth, syncing your chat, all with a single setup.  Want to see how it fits into your workflow, sign up and try it out. Or talk to us we’re happy to help.