Why Are Stream Alerts Delivered as WEBM?
1 min read
Stream alerts — every Flix Store alert among them — are delivered as WEBM because it is a lightweight video format that supports a transparent background, so the alert plays over your stream with no black box around it.
How the formats differ
| Format | Transparent background | Sound | Notes |
|---|---|---|---|
| WEBM | Yes | Yes | Lightweight; works in OBS, Streamlabs and StreamElements |
| MP4 | No | Yes | Plays with a full background; right for intros and ordinary videos |
| GIF | Limited | No | Fewer colors and a larger file |
Where else WEBM is used
- Transitions: cover the screen as you switch between two scenes.
- Animated frames and screens: stay over the camera or the game for the whole stream.
How to try an alert file in OBS
- In Sources, click + and choose Media Source.
- Turn on Local File and choose the alert file.
- Watch it over your scene and check that the background is transparent.
This is for trying it only. On a real stream, alerts are uploaded to an alert tool so they play by themselves on every donation.
Common problems
- A black background behind the alert: the file is an MP4, or was not exported with transparency. Ask for a WEBM version.
- Choppy motion: the file is larger than the stream. Use a file at the stream's own size.
Every Flix Store alert is delivered as a WEBM with a transparent background. For adding one step by step, read how to add an alert in OBS.