Set a Video's Audio Bitrate
Pick a video and a target audio bitrate — its soundtrack is re-encoded in your browser while the picture is copied untouched. Nothing is uploaded.
Shrink a video's audio without touching the picture
Pick a video, choose a target audio bitrate, and get the same clip back with a smaller, re-encoded soundtrack. The picture is stream-copied (not re-encoded), so it stays byte-for-byte identical and processing is fast — only the audio track is re-encoded to the bitrate you pick. Everything runs in your browser; nothing is uploaded.
Why change the audio bitrate?
A lot of clips carry a soundtrack recorded at 256–320 kbps (or higher) when the audio is only speech. Dropping it to 96–128 kbps can shave megabytes off the file with no visible change to the video and little audible change to talking. Because the video is copied untouched, the whole file is only as big as its picture plus the smaller audio you chose.
Picking a bitrate
- 64–96 kbps — voice, podcasts, screen recordings, narration. Smallest files; fine for speech.
- 128 kbps — the default. A good balance for stereo music or mixed speech and music.
- 160–192 kbps — keeps music sounding clean.
- 256–320 kbps — near-transparent quality; use when the soundtrack matters and file size doesn't.
Worked example: a 40 MB screen recording whose audio is a 320 kbps stereo
track of someone talking. Load recording.mp4, pick 96 kbps, and you get
recording-audio.mp4 — the same video, an audio track a fraction of the size,
and a noticeably smaller overall file.
Notes and limits
- The video stream is copied losslessly; the output keeps the same container (mp4 → mp4, webm → webm). WebM audio is re-encoded to Opus, everything else to AAC.
- Bitrate is constant (CBR) — the same target across the whole clip.
- This lowers (or raises) the audio bitrate; it does not re-encode or shrink the picture. To make the video smaller, use a video-compression tool instead.
- Input and output are each capped at 25 MB (the file is processed in your browser's memory).
FAQ
Is my video uploaded to a server?
No — ffmpeg runs inside your browser tab, so the file never leaves your device.
Will changing the audio bitrate hurt the video quality?
No. Only the audio is re-encoded; the picture is stream-copied without re-encoding, so the video quality is identical to the original.
Does a lower bitrate make the whole file smaller?
Yes, for the audio portion. The video stream is copied unchanged, so the total saving equals the difference between the old and new audio bitrates times the clip length. On a talky clip with a high-bitrate soundtrack that can be several megabytes.
Can I raise the bitrate to improve quality?
You can pick a higher value, but re-encoding lossy audio to a higher bitrate cannot recover detail that was already discarded — it only makes the file bigger. Raising the bitrate makes sense only when the source audio is high-quality to begin with.
Which video formats can I use, and how big can the file be?
Anything ffmpeg can read — mp4, mov, mkv and webm are the common cases. The
output keeps the input's container and is named after the original with an
-audio suffix (e.g. clip.mp4 → clip-audio.mp4). WebM audio is re-encoded
to Opus and everything else to AAC. The input and output are each capped at
25 MB.
Developer & Automation Access
Run it from the terminal
Same engine as this page, headless — via the gizza CLI:
gizza tool video-audio-bitrate-set 'url=https://example.com/input' 'bitrate=128'New to the CLI? Get gizza →
Open it by URL
Pre-fill and auto-run this tool with query parameters — the names match the API/CLI:
https://gizza.ai/tools/video-audio-bitrate-set/?url=https://example.com/input&bitrate=128Machine-readable descriptor: tool.json — title + parameters JSON Schema for agents.