Does WebM keep the alpha channel from my ProRes 4444 MOV?

Yes — VP9 in WebM supports transparency, and the size reduction on alpha video is enormous compared to ProRes 4444. The caveat is Safari, which handles transparent video via HEVC-with-alpha in MOV instead, so cross-browser sites ship both files and let the browser pick.

Why is the conversion taking so long?

VP9 encoding is computationally heavy — several times slower than H.264 encoding at comparable settings, and AV1 is slower still. For long footage, expect multiple minutes of processing per minute of HD video; the payoff is the smaller, royalty-free output.

What happens to the audio track?

AAC or PCM audio from the MOV is re-encoded to Opus, since WebM cannot legally carry AAC. Opus at 128 kbps is transparent for most material, so the audible difference is nil even though the audio is technically transcoded.

MOV to WEBM Converter – Free & Online

Convert MOV to WEBM

Turn MOV files into WEBM in seconds — free, secure, and no signup required.

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iPhone and ProRes footage becomes compact, royalty-free web video when converted from MOV to WebM with VP9 and Opus inside. Browsers play the result natively, and the files are usually far smaller than the QuickTime source.

Convert MOV to WEBM – Free Online MOV to WEBM Converter

Why convert MOV to WEBM?

Publish Mac-edited video on the open web without H.264 licensing entanglements or plugin requirements.
Shrink hero-section and background videos for faster page loads — VP9 typically undercuts H.264 by 30-50% at matching quality.
Ship animations with transparency: VP9 WebM carries an alpha channel, replacing enormous ProRes 4444 files in web contexts.

Tip: The alpha-channel trick is the killer feature here — a transparent ProRes 4444 overlay weighing hundreds of megabytes often lands under 10 MB as VP9 WebM with the transparency intact.

How to convert MOV to WEBM

Upload your MOV file using the area above.
WEBM is preselected as the target format.
Click Start and wait for the conversion to finish.
Download your converted WEBM file.

Convert MOV to WEBM

Convert MOV to WEBM – Free Online MOV to WEBM Converter

Why convert MOV to WEBM?

How to convert MOV to WEBM

MOV to WEBM — Frequently Asked Questions