Formats and when to use them
| Format | Encoder | Best for |
|---|---|---|
| MP3 | LAME (LGPL) in WebAssembly | Anything: every player, car stereo and phone plays MP3 |
| M4A (AAC) | Browser's AAC encoder | Apple devices and podcasts; better than MP3 at the same bitrate |
| Opus (.ogg) | Browser's Opus encoder | Smallest files for speech; modern players and browsers |
| WAV | None (uncompressed) | Editing in an audio program; large files |
The tool says which encoder it used with each result. If this browser cannot encode AAC (some Linux builds), choose MP3 or Opus instead.
Choosing a bitrate
Bitrate decides size and quality: 128 kbps is about 1 MB a minute. For a recorded lecture, meeting or podcast, 96 kbps is clear and small. For music, 192 kbps MP3 is hard to tell from the original on most headphones; 256 to 320 kbps leaves headroom. Choosing a bitrate higher than the source's sound (often 96 to 128 kbps in phone videos) only makes the file bigger.
Common uses
- Turn a recorded talk or webinar into a podcast-style file to listen to on the move.
- Pull a voice memo or interview out of a video for transcription.
- Keep the soundtrack of a home video you made.
Respect copyright: extract audio only from videos you made or have permission to use.
Speed
Extracting audio is fast because the video does not need to be decoded: a 10-minute video usually takes a few seconds. WAV is fastest of all, since it needs no encoding.
Why audio is small next to video
A video file is mostly its bitrate (how many bits are spent per second) multiplied by its duration. A 2-minute clip at 2 megabits per second is about 2 × 120 ÷ 8 = 30 MB, plus the sound. Everything else matters only through the bitrate it needs to look good:
- Resolution. 1080p has 2.25 times the pixels of 720p, so it needs roughly twice the bitrate for the same sharpness. Below a certain bitrate, a smaller resolution looks better than a blocky big one, which is why the automatic setting steps down.
- Frame rate. 60 fps needs more bitrate than 30 fps; for talking, screen recordings and most phone clips, 30 or even 24 fps is plenty.
- Movement and detail. A static screen recording compresses far better than handheld footage of a crowd, confetti or water. Two videos of the same length and settings can differ several-fold in size.
- Codec. H.264 plays everywhere. VP9, HEVC (H.265) and AV1 give the same quality in 30 to 50% fewer bits but are not supported by every player or upload form.
- Sound. Usually small: 96 kbps stereo is about 0.7 MB a minute. Removing it helps only for very small targets.
Browser support and troubleshooting
The line at the top of the tool lists the video and audio codecs this browser can encode. Current Chrome and Edge on Windows and Mac handle H.264, VP9 and AV1 with AAC and Opus; Safari adds HEVC; Firefox supports WebCodecs from version 130. If a file will not open:
- "This browser cannot decode…" usually means HEVC (H.265) video, common from iPhones, in a browser without HEVC support. Try Safari or Edge on a computer with hardware HEVC, or convert it on the phone (Settings › Camera › Formats › Most Compatible for future videos).
- "Cannot read this file's format" means an old or unusual container such as AVI, WMV or FLV that browsers cannot read. Convert it with HandBrake first.
- It stops or the tab reloads on long or 4K videos: the tab ran out of memory. Trim the video into parts, close other tabs, or use a desktop app.
- Very slow on a phone or an older laptop: the browser may be using software encoding. Shorter clips and lower resolutions help.
Troubleshooting
- "This file has no sound": some screen recordings and exported clips have no audio track at all. Check the video plays with sound in your media player.
- The MP3 is silent: the video's audio track may be silent (for example a muted recording) even though it exists.
- AAC is missing from the list of encoders: some browsers on Linux cannot encode AAC. Choose MP3 or Opus.
File names and tags
The audio file is named after the video. Title, artist and album tags are not added; set them in your music app after importing if you want the file to show up properly in a library.
Privacy
Your video never leaves your device. It is read and written in the browser tab; there is no upload, no server-side processing and no account. You can disconnect from the internet after the page has loaded and it still works. Free use has no watermark and covers files up to 500 MB and 10 minutes; the A$9 lifetime licence removes those limits (your device's memory still applies), queues up to 20 files and saves presets.