PNG sequence to transparent WebM.
Upload a ZIP of transparent PNG frames—from After Effects, Blender, Unity or Spine—and download a WebM with a real VP9 alpha channel. No FFmpeg, no command line.
Good to know.
How should the frames be named?+
Any names work; frames are ordered naturally, so frame_2.png comes before frame_10.png. Put only the PNG frames in the ZIP, up to 900 of them.
Why WebM and not MP4?+
H.264 MP4 cannot store transparency. WebM with VP9 alpha plays transparently in Chrome, Firefox, Edge and OBS. Safari ignores WebM alpha—see the black background guide.
What is the FFmpeg equivalent?+
ffmpeg -framerate 30 -i frame_%04d.png -c:v libvpx-vp9 -pix_fmt yuva420p -auto-alt-ref 0 -b:v 0 -crf 32 output.webm. The yuva420p pixel format carries the alpha; without it the result is opaque.
My frames have no transparency.+
The converter checks the first frame. PNGs saved without an alpha channel are refused, because the WebM would be opaque too.
Is it really free?+
Yes. Sign in with Google and convert up to 10 files a day without credits. Files up to 30 seconds, 1080p, 30 fps and 100 MB. Results stay in My videos for 7 days.