Video and audio tools
Kilnfile's video and audio tools convert, trim, compress and re-encode media files using FFmpeg compiled to WebAssembly, so the work happens on your device rather than on a server. There is no upload, no signup and no watermark. Larger files take longer, but a typical phone clip finishes in under a minute.
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All video and audio tools (10)
MediaMP4 to MP3Pull the soundtrack out of any MP4 and save it as an MP3 at the bitrate you choose.MediaMOV to MP4Turn QuickTime MOV files into MP4 that plays anywhere, in seconds, without leaving your browser.MediaCompress VideoCut a video's file size by more than half without it leaving your device.MediaTrim VideoKeep just the part of a video you want, cut in your browser with nothing uploaded.MediaVideo to GIFPick a few seconds of any video and turn them into a sharp, looping GIF.MediaMP3 to WAVDecode MP3 files to standard PCM WAV that any editor, DAW or CD burner will accept.MediaWAV to MP3Shrink bulky WAV recordings to MP3 at the bitrate you choose, entirely in your browser.MediaM4A to MP3Turn iPhone voice memos and other M4A or AAC audio into MP3 that plays everywhere.MediaExtract Audio from VideoSave the soundtrack of any video as MP3, WAV or an untouched M4A copy.MediaChange Video SpeedMake a video faster or slower, from quarter speed to 4x, with the audio kept in tune.
| Tool | Accepts | Batch | Updated |
|---|---|---|---|
| MP4 to MP3 | .mp4, .mov, .webm, .mkv, .avi, .m4v | Yes | 20 September 2026 |
| MOV to MP4 | .mov, .qt | Yes | 20 September 2026 |
| Compress Video | .mp4, .mov, .webm, .mkv, .avi, .m4v | Yes | 20 September 2026 |
| Trim Video | .mp4, .mov, .webm, .mkv, .avi, .m4v | No | 20 September 2026 |
| Video to GIF | .mp4, .mov, .webm, .mkv, .avi, .m4v | No | 20 September 2026 |
| MP3 to WAV | .mp3 | Yes | 20 September 2026 |
| WAV to MP3 | .wav | Yes | 20 September 2026 |
| M4A to MP3 | .m4a, .aac | Yes | 20 September 2026 |
| Extract Audio from Video | .mp4, .mov, .webm, .mkv, .avi, .m4v | Yes | 20 September 2026 |
| Change Video Speed | .mp4, .mov, .webm, .mkv, .avi, .m4v | No | 20 September 2026 |
Uploading a video to a converter site is slow and puts a copy of your footage on someone else's server. These tools load FFmpeg into your browser once (about 30 MB, cached afterwards) and then work offline.
Common jobs include ripping the audio from an MP4, converting iPhone MOV files for Windows, trimming a clip, shrinking a video for WhatsApp, and turning a short clip into a GIF.
Guides for video and audio tools
- How to convert MOV to MP4 on WindowsConvert iPhone MOV videos to MP4 on Windows in your browser, no software. When a 5 second remux is enough and when HEVC clips need re-encoding.
- How to shrink a video for WhatsAppGet a video under WhatsApp's 16 MB media limit in your browser, or send it as a document up to 2 GB at full quality. Settings and real file sizes.
- How to make a GIF from a videoTurn a clip into a GIF in your browser: pick the start, duration, frame rate and width, and keep the file under the limits for Slack, X and websites.
- Audio formats and bitrates explainedMP3, AAC, WAV and FLAC compared with real file sizes per minute. Which bitrate you can actually hear, and when converting loses nothing at all.