Add a Silent Audio Track to a Video
Pick a video with no sound and get it back with a silent audio track added, so tools that demand an audio stream stop rejecting it. The picture is copied untouched and nothing is uploaded.
Give a silent video the audio stream other tools insist on
Plenty of files have a picture but no sound at all: screen captures, exported renders, timelapses, GIF conversions, drone clips. That is perfectly valid video — but a lot of uploaders, editors, ad platforms and playback pipelines assume every file has an audio stream, and reject or mangle the ones that don't. The standard fix is to add a track of pure digital silence.
This tool does exactly that. Load a video, and it comes back with a silent audio
track attached. The picture is stream-copied (-c:v copy) — not re-encoded —
so it stays byte-for-byte identical, the file processes in seconds, and nothing
is uploaded: ffmpeg runs inside your browser tab.
What it does under the hood
The silence isn't a file you have to supply — it is generated on the fly by
ffmpeg's anullsrc source at the channel layout and sample rate you pick, then
muxed alongside your untouched video and bounded to the video's exact length.
Worked example: screencast.mp4 is a 12 MB, 3-minute H.264 recording with
no audio stream, and an upload check keeps failing it. Load it here with the
defaults (stereo, 48 kHz, 128 kbps) and you get screencast-silent-audio.mp4:
the same 3-minute H.264 picture, unchanged, now carrying one AAC audio track of
silence — and the upload goes through.
The options
- Channels —
stereo(default) is what most validators expect;monois half the size and still a perfectly valid audio stream. - Sample rate —
48000Hz (default) is the video-world standard,44100Hz matches CD/editor conventions,22050Hz keeps the added bytes smallest. - Audio bitrate —
128kbps is the universally accepted default. Silence sounds the same at every setting, so32–64kbps is a good choice on a long clip;192kbps is there for checks that demand a higher rate. - If the video already has audio —
replace(default) leaves exactly one track in the output, the silence, so the clip ends up muted.keeppreserves the original track and adds the silence as a second track. On a video with no audio the two behave identically.
Notes and limits
- The video stream is copied losslessly — the picture, resolution, frame rate and duration are untouched.
- The output keeps the input container (mp4 → mp4, mov → mov, mkv → mkv, webm → webm). Any other container falls back to mp4.
- WebM output uses Opus at 48 kHz — that is the only rate Opus encodes, so a 22.05/44.1 kHz choice is pinned to 48 kHz there. Every other container uses AAC at the rate you picked.
keepre-encodes the existing audio track at the chosen bitrate (it can't be copied while a filter-generated track is being added in the same pass).- Input and output are each capped at 25 MB — the file is processed in your browser's memory.
- This adds an audio stream; it does not add sound. If you want to attach real music or narration, that needs a second media file and a different tool.
FAQ
My video already plays fine — why would I add silent audio?
Because something downstream requires an audio stream. Upload validators, ad platforms, some NLE timelines, hardware players and automated encoding pipelines routinely error out, drop the file, or produce a broken result when a video carries no audio track at all. A silent track satisfies the requirement without changing anything you can see or hear.
Does this re-encode or degrade my video?
No. The picture is stream-copied with -c:v copy, so the video stream in the
output is bit-identical to the input. Only the new audio track is encoded, and
it contains nothing but silence.
What's the difference between "no audio track" and "a muted audio track"?
A video with no audio track has zero audio streams — that's what trips up
strict tools. A muted video has an audio stream whose samples are all zero.
This tool turns the first into the second. If your file already has an audio
stream and you simply want it silenced, choose replace: the existing track is
dropped and a silent one takes its place.
How much bigger does the file get?
Very little. Silence compresses extremely well, and the added track is roughly the bitrate you choose times the clip length as an upper bound — at 32 kbps that's about 240 KB per minute at worst, usually far less. The video stream, which is the bulk of the file, is copied unchanged.
Which formats work, and how large can the file be?
Anything ffmpeg can read; mp4, mov, mkv and webm are the common cases and each
keeps its own container. The output is named after the original with a
-silent-audio suffix (e.g. clip.mp4 → clip-silent-audio.mp4). WebM gets an
Opus track at 48 kHz, everything else an AAC track. Input and output are each
capped at 25 MB.
Is my video uploaded anywhere?
No. ffmpeg runs as WebAssembly inside your browser tab, so the file never leaves your device.
Developer & Automation Access
Run it from the terminal
Same engine as this page, headless — via the gizza CLI:
gizza tool video-add-silent-audio 'url=https://example.com/input' 'channels=stereo' 'sample_rate=48000' 'bitrate=128' 'existing_audio=replace'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-add-silent-audio/?url=https://example.com/input&channels=stereo&sample_rate=48000&bitrate=128&existing_audio=replaceMachine-readable descriptor: tool.json — title + parameters JSON Schema for agents.