Sources & Method

All factual claims in our guides are backed by official documentation, technical specifications, or research papers. This page lists every source referenced across the site, with retrieval dates.

Video Formats and Codecs

Browser Support and Compatibility

  • Safari WebM alpha limitation (WebKit bug #275908): WebKit Bugzilla (Retrieved: October 9, 2026). Status was NEW. The report says a grey background rather than transparent. A Linux Playwright WebKit 26.0 build crashed when a video source was set, so it was not used as a color measurement. That build is not macOS Safari. Chromium 140 composited a magenta page through a VP9 alpha WebM the same day.
  • Jake Archibald: Video with transparency (2024): Article (Retrieved: August 19, 2026)
  • CSS-Tricks: Overlaying Video with Transparency: Article (Retrieved: August 19, 2026)

Encoding Tools and FFmpeg

  • FFmpeg VP9 encoding guide: FFmpeg Wiki (Retrieved: August 19, 2026). The wiki did not return article text on October 9, 2026 (bot check), so new pages do not quote it.
  • FFmpeg filters (chromakey, colorkey): ffmpeg-filters.html (Retrieved: October 9, 2026). chromakey is documented as YUV color keying. colorkey is documented as RGB color keying, default key color black. The green, black, and white commands on the MP4-to-WebM guide were run the same day on FFmpeg 6.1.1 with libvpx 1.14.0.
  • Shotcut forum on MP4 alpha limitations: Forum discussion (Retrieved: August 19, 2026)

AI Video Matting Research

  • Robust Video Matting (RVM): Project page (Retrieved: August 19, 2026)
  • RVM paper: arXiv 2108.11515 (Retrieved: August 19, 2026)
  • Note: RVM is cited to explain temporal consistency in video matting. It is not a description of ExportAlpha's processing stack.

OBS Studio

  • OBS Media Sources: Official Knowledge Base (Retrieved: October 9, 2026). Listed video types: .mp4, .ts, .mov, .flv, .mkv, .avi, .gif, .webm. The page includes Apply alpha in linear space.
  • OBS Browser Source: Official Knowledge Base (Retrieved: August 19, 2026)
  • OBS Track Matte Stinger Transitions: Official Knowledge Base (Retrieved: September 8, 2026)

Background Removal and Editing Tools

Method and Processing

Public product facts we can state:

  • Authentication: Google sign-in
  • Payments: Stripe Checkout, Billing, and Customer Portal

Default export: VP9 WebM with yuva420p pixel format, background_color set to Transparent

Optional export: ProRes 4444 MOV

Service limits (v1): Maximum 60 seconds, 1080p, ~200MB per file, 1 concurrent job

Retention: Results and uploads from finished jobs are deleted automatically 7 days after processing finishes. Uploads that never finish processing (failed or abandoned) are deleted automatically 7 days after upload.

Known gaps

The following are documented as unknown or untested as of August 19, 2026:

  • HEVC-with-alpha in Safari: We have not verified Safari transparency with our own HEVC exports. Treat that path as experimental.
  • Duration and resolution: We enforce 60 seconds and 1080p on upload.
  • CapCut, iMovie, DaVinci Resolve WebM alpha import: Public documentation is contradictory. Users should test with their specific software version.
  • HEVC support in OBS on Windows/Linux: May depend on system codecs. VP9 WebM is the recommended cross-platform format.

Updates and Corrections

This page is updated when:

  • New guides are added
  • Referenced specifications or documentation change
  • Pricing or service limits are adjusted
  • Gaps are resolved through testing

Last updated: October 9, 2026

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