FLV to WebM (VP9) - Online Video Converter
Convert FLV to WebM (VP9) online. Private, client-side - no uploadrequired. Batch conversion, quality presets, codec control.
About FLV to WebM (VP9)
FLV is Adobe's Flash-video container carrying Sorenson Spark or H.264 streams with MP3 or AAC sound. WebM re-encodes the picture to VP9 with Opus audio for current browsers, since Flash-era players are gone. H.264 sources near the target settings re-encode with small losses, while Sorenson sources need full decoding first. The converter writes a fresh index, which repairs sparse Flash seek tables. Verify duration and sync after conversion, because variable timestamps in old files can drift.
Why convert FLV to WebM (VP9)?
- Smaller files with WebM lossy compression.
- Keep animation and transparency where supported.
- Private, no upload - runs in your browser.
FLV vs WebM (VP9)
| Animation | Yes | Yes |
|---|---|---|
| Transparency | No | Yes |
| Compression | lossy | lossy |
| Typical use | FLV is Adobe's Flash-video container carrying Sorenson Spark or H.264 streams. | WebM pairs VP9 video with Opus audio and supports an alpha channel. |
When not to convert FLV to WebM (VP9)
- Skip WebM for archival masters: lossy compression discards detail, so keep the FLV original.
- Keep a master copy: repeated exports stack small losses, so archive FLV before batch WebM shares.
Limits
Starting point: FLV - FLV is Adobe's Flash-video container carrying Sorenson Spark or H.264 streams. Flash-era players are gone, so convert for current browsers. Apple editors accept it unevenly; keep MP4 for editing round-trips. Encode WebM (VP9 / Opus) from FLV at a bitrate near the source, and confirm the audio track before converting.
How conversion works
Conversion runs entirely in your browser with FFmpeg WASM. Files never leave your device.