I shipped a transparent-video exporter because “remove background” usually just means a black fill

I kept hitting the same search after “AI remove video background”: why is the result a black rectangle? Does MP4 even carry transparency? Why is the WebM fine in Chrome and black in Safari? How do I drop this into OBS without chroma-keying a green screen that was never there?

The answer is usually not “the model failed.” Everyday H.264 MP4 does not carry an alpha channel. A lot of players composite transparent pixels onto black. Safari ignores WebM alpha. So I shipped ExportAlpha — a small exporter that writes a real alpha channel: transparent WebM (VP9, yuva420p) for Chrome, Firefox, and OBS, or ProRes 4444 MOV for Premiere, Resolve, and Final Cut.

ExportAlpha homepage. Official product screenshot. Source: exportalpha.com.

Fifteen free seconds on first Google sign-in. No card required to try a short clip. Upload is MP4 / MOV / WebM / M4V, up to 60 seconds, 1080p, 200MB. It is a file workflow, not a live-stream plugin.

What I refused to invent

The site has a public Sources & Method page. Retrieval dates are 19 August 2026. A few gaps stay labeled instead of being filled in:

• HEVC-with-alpha for Safari is the correct destination format on paper (WWDC 2019 Session 506). We have not verified Safari transparency on our own exports. The sources page marks that feature experimental.
• CapCut / iMovie / DaVinci Resolve importing WebM-with-alpha: public docs contradict each other. The format guide says test your version; if WebM fails, use ProRes 4444.
• HEVC inside OBS on Windows/Linux depends on system codecs. The OBS guide recommends VP9 WebM as the cross-platform overlay.

I also do not claim this is real-time webcam matting. The OBS page says it in plain language: no virtual camera, no live filter, no stream plugin. You upload a clip, download a file, then add a Media Source.

The model stack is listed on that same sources page: fal.ai calling Bria VRMBG 3.0. RVM is cited only as a paper on temporal consistency, not as the production model.

The searches that became pages

Each URL is a question people already type. The page answers it, then links the dated source.

• Why does my transparent video have a black background? — alpha was never written, or the player composites onto black. Check ffprobe for yuva420p / yuva444p10le / rgba, or drop the file over a colored plate in an NLE.
• Does MP4 support a transparent background? — everyday H.264 does not. Do not export H.264 if you need transparency.
• Which transparent video format should I export? — WebM for Chrome/Firefox/OBS; HEVC-with-alpha for Safari (we have not verified our own HEVC); ProRes 4444 for editors; already-composited H.264 only as a finished deliverable.
• Why is my transparent WebM black in Safari? — Safari ignores WebM alpha. Chrome and Firefox composite it.
• How do I make a WebM video with a transparent background? — VP9 with yuva420p, or FFmpeg if you already have alpha.
• Can I use a transparent video overlay in OBS? — Media Source + local WebM, or Browser Source for a hosted page. Do not add a Chroma Key filter if the file already has alpha.
• Why does AI video background removal flicker? — frame-by-frame masks drift; a temporal video model keeps edges stable.
• What is a video alpha channel? — the fourth channel. Without it, “transparent” regions become black.

Homepage examples: hair, hand overlay, home-office talking head, product. Official product screenshot. Source: exportalpha.com.

Guide: black background is usually format or playback, not a failed job. Official product screenshot. Source: exportalpha.com/guides/why-transparent-video-has-black-background.

Decision table: WebM vs HEVC vs ProRes vs composited MP4. Official product screenshot. Source: exportalpha.com/guides/what-transparent-video-format.

OBS: Media Source + VP9 WebM. Not a live camera plugin. Official product screenshot. Source: exportalpha.com/guides/how-to-use-transparent-video-in-obs.

Pricing as it sits on the page today

Credits: 1 credit = 1 started second. New accounts get 15 seconds. Plan credits reset monthly; pack credits never expire. Failed jobs refund credits. Successful exports do not. Checked on the live homepage, 25 August 2026.

Monthly: Creator $19 (1,200 seconds), Pro $39 (3,000 seconds), Studio $79 (7,200 seconds). Annual is shown as $15.83 / $32.50 / $65.83 per month ($190 / $390 / $790 billed once). One-time packs: Quick $5.99 / 240s, Starter $9.99 / 480s, Plus $29.99 / 1,800s.

Homepage pricing. Official product screenshot. Source: exportalpha.com/#pricing.

What it will not do

Copied from the site’s own “We can’t” list: restore quality lost to heavy compression, act as a real-time live-stream plugin, bypass content safety, or process clips longer than 60 seconds. Adult content, minors, and non-consensual use are blocked. Results are kept 7 days, then deleted.

If you are exporting a stream alert, a lower-third, or a talking-head overlay and you keep getting a black plate: the file probably never had alpha, or the player is lying to you. Export WebM or ProRes 4444, then test over a colored background.

Live tool: https://exportalpha.com/