Raids are the most underrated growth moment in Twitch streaming. When another channel ends its broadcast and points its whole live chat at you, you get a spike of viewers who are actively looking for somewhere to land. A good raid alert turns that ten-second window into a follow — and a weak one lets all of them drift away.

This guide covers Twitch raid alerts from the ground up: what a raid actually does, how one is triggered and received, how to add a raid alert to OBS with a transparent WebM file (or a Browser Source), and how to design the alert so it converts raided viewers instead of just announcing them.

What a Raid Is (and Why Raid Alerts Matter)

A raid sends everyone connected to chat at the time of the raid to the recipient channel, according to Twitch's official raids documentation. It is not a hosted stream — it redirects live viewers from the outgoing channel to yours. The target channel gets a chat message announcing the raid and the number of raiders who joined.

That is a high-intent audience. These are people who just finished someone's stream and chose to keep watching together. Twitch's own guidance for handling an incoming raid is to thank the streamer and the raiders, introduce yourself, and keep it short and genuine. A raid alert is the visual version of that introduction — your first impression, and it should make raiders feel welcome rather than interrupted.

How a Twitch Raid Works, Step by Step

Understanding the mechanics helps you design around them. To start a raid, a broadcaster types /raid followed by the target channel name, or uses the Raid Channel quick action in the Creator Dashboard. A pop-up in chat tracks the number of participants and runs a countdown; viewers can opt out before it begins. After about ten seconds — or when everyone is ready — the broadcaster clicks Raid Now, and everyone connected to chat is redirected to the target channel. If nobody clicks, the raid starts automatically when the countdown depletes. Twitch's How to Use Raids article covers this in full.

On the receiving side, a raided channel controls who is allowed in. Incoming Raid Settings let you set a minimum and maximum viewer count, a minimum account age for the raiding channel, and optional groups such as teammates. A channel that is offline, blocked, or below your thresholds cannot raid you. Broadcasters can also pause all incoming raids for up to an hour while live using a Stop Raids for 1 Hour quick action.

The practical takeaway: raids arrive in a burst, with no warning, at the end of someone else's stream. Your raid alert has to load instantly and play once — no looping, no lag, no black box — because the whole thing lasts only a few seconds.

Which Events Can Trigger a Raid Alert

Twitch treats raiding as a first-class alert event. In Twitch's own alerts setup, the alerts editor includes Raids as one of the events you can build variants for, alongside Follows, Subscriptions, Hype Train, Goals, Charity, and Cheering. You can even create raid variants based on conditions such as the number of raiders, so a small raid gets a quieter thank-you and a big one gets something bigger.

If you use a dedicated alert tool instead of Twitch's built-in alerts, raid alerts are a standard supported type. AlertForge covers follower, subscriber, donation, raid, bits, and gift-sub alerts. You generate the alert as a transparent WebM and drop it into OBS, while your event source supplies the trigger.

Transparent WebM vs. Browser Source for Raid Alerts

You have two main ways to display a raid alert in OBS, and each suits a different workflow.

Transparent WebM (Media Source). A WebM file with an alpha channel carries its transparency natively. According to OBS's Media Sources documentation, Media Source supports .webm among its video file types and exposes an "Apply alpha in linear space" option for accurate alpha compositing. Because the transparency is baked into the file, you do not need a chroma key or a green screen to layer the alert over your gameplay. You control exactly when it plays, which makes it predictable for a one-shot event like a raid.

Browser Source. OBS's Browser Source is literally a web browser embedded in your scene, rendering the page (including video) on top of your stream. OBS's Browser Source documentation notes that its default custom CSS makes the page background transparent. Alert services that hand you a URL — including Twitch's own alerts — plug in here. The trade-off is that a Browser Source is heavier and, unless your service fires the alert from a live feed, it relies on the service to trigger it rather than on a local file you control.

For a raid alert in particular, a transparent WebM in a Media Source is usually the cleaner choice: it is lightweight, plays exactly once, and never depends on a third-party feed staying up at the exact moment a raid lands.

How to Add a Transparent WebM Raid Alert to OBS

The setup is short, and the exact steps are in the how-to block at the end of this article. First, make sure your raid alert is a WebM that actually has alpha — a regular MP4 will not be transparent and will show a black background. If you generated the alert with a tool like AlertForge, choose the transparent WebM export (VP9 WebM with alpha) rather than the green-screen MP4 fallback.

Then, in OBS: open the scene where the alert belongs, add a Media Source pointed at your .webm file, turn Loop off, keep "Restart playback when source becomes active" on, and turn on "Show nothing when playback ends" so the alert disappears cleanly instead of freezing on its last frame. Trigger a test alert and confirm it plays over your game with a fully transparent background.

What to Put Inside a Raid Alert

A raid alert that converts viewers does more than say "raid." It should do four things, fast:

Acknowledge the source. Show the raiding channel's name, and optionally the raider count. People came from somewhere; naming it feels personal and genuine.
Welcome the new audience. A short message like "welcome raiders" sets the tone. Twitch's own advice for incoming raids is to thank everyone and introduce yourself — your alert is the on-screen version of that first sentence.
Prompt the next action. The point is to keep people around. A subtle nudge — "if you're new, drop a follow" — materially raises the chance the burst becomes a lasting audience.
Stay short. Raids last a few seconds. An alert that runs for ten seconds is gone from view by the time it finishes. Keep the animation tight.

Designing a Raid Alert That Matches Your Brand

Raid alerts are stream branding as much as they are alerts. If your follow, sub, and donation alerts share a visual language — same colors, same font, same motion style — a raid alert that matches them makes the whole package feel professional. If it clashes, it looks like an afterthought.

Because AlertForge generates the rest of your alert set from a single approved Style Sheet, a raid alert can inherit the same palette, typography, and motion as your other alerts instead of being a separate, unrelated file. For streamers who want viewer-requested alerts on top of the standard set, there is also a viewer alerts option where viewers pay to request a custom alert for your overlay.

The pattern that works: settle on a consistent visual identity first, then make every alert — including the raid alert — an expression of it.

Common Raid Alert Problems and Fixes

Black box instead of transparency. Your file is probably a WebM without an alpha channel, or an MP4. Re-export with VP9 + alpha (the transparent WebM option), and check that you did not add a chroma key filter to the Media Source.
Alert plays on a loop. Turn Loop off and enable "Show nothing when playback ends."
Alert is slow to appear. A local WebM in a Media Source is nearly instant. If you use a Browser Source, keep it to a single URL and consider "Shutdown source when not visible" so it is not using resources all stream.
Raid fires but nothing shows. Confirm the alert source is in the active scene, that you triggered the correct event, and that the file path is valid.

Raid Alerts as Part of a Broader Alert Strategy

Twitch raid alerts are one small moment in a larger ecosystem of follow, sub, and donation alerts. The channels that look cohesive treat all of them as one system. When you build or refresh yours, plan the full set together rather than bolting on alerts one at a time — and put the raid alert at the same quality bar as the rest. The same transparent-WebM-in-OBS approach carries over to OBS alerts generally, and to Kick alerts and YouTube live alerts on other platforms.