Convert an Audacity project to MP4 video
Video sites and phones take a video file, and an Audacity project is not even an audio file. Drop an .aup3 or .aup4 here and export an MP4: the mix as AAC sound with a still picture — the project's name and waveform, or an image of yours. Nothing is uploaded.
Several projects? Drop or choose them together: export them all to one ZIP at once (Pro), or open them one by one free.
How do I convert an Audacity project (.aup3 or .aup4) to MP4?
Export it with a picture. An .aup3 or .aup4 is an Audacity project — an SQLite database of audio blocks and a document saying how they play — not a media file, and Audacity's own export (File → Export Audio) writes audio files. Drop the project on this page, choose MP4 · video and export: the mix becomes AAC sound and a still picture — the project's name and waveform, or an image you pick — becomes 1280×720 H.264 video, in one .mp4 that video sites and phones take. Nothing is uploaded; MP4 export is part of Pro.
Drop an .aup3 or .aup4 project (with its -wal, if one sits beside it).
Pick MP4 · video. The picture shows the project's name, length and waveform; Use my image shows a picture of your own instead.
Export: the mix is encoded as AAC sound, then the still picture as H.264 video, into one .mp4.
MP4 export is part of Pro; the stereo mix as MP3 or WAV is free for projects up to 256 MB.
Convert an Audacity project to MP4 video
People ask for an MP4 when a recording has to go somewhere that only takes video: a YouTube upload, a message on a phone, a slide in a presentation. Audacity's own export writes audio files, so the usual route is an MP3 first and then a video editor to put a picture under it. Here the project is read in the browser, the mix is rendered once, and the browser's own encoders turn it into one .mp4 — 1280×720 H.264 with AAC sound.
MP4 export is part of Pro; the stereo mix as MP3 or WAV stays free for projects up to 256 MB.
On a Mac? Audacity's own recovery utility only gained a macOS build in January 2026, and it is still a terminal program that asks for about four times the project's size in free space. Everything on this page runs in the browser instead, on any operating system.
How the MP4 is put together
An .mp4 is an ISO base media file: an index box (moov) describing each track, then the media data (mdat). Waveward writes two tracks — AAC sound and H.264 picture — with the index first, and the media data as two runs: every packet of sound, then every frame of picture. The sound can be written while it is encoded and the picture after it, so neither has to be held in memory, and the index is filled in at the end from the sizes the encoders reported.
The picture is drawn on a canvas in the page's worker and handed to the browser's H.264 encoder (WebCodecs' VideoEncoder) in its "avc" format: length-prefixed NAL units, with an AVCDecoderConfigurationRecord as the decoder configuration, which goes into the file's avcC box as it is. The same picture is encoded once a second for the length of the mix, a keyframe every 10 seconds; the frames in between are a few hundred bytes each, because nothing in them changes. High profile is asked for first, then Main, then Baseline, whichever the browser's encoder takes.
The sound is the M4A export's: the mix rendered a window at a time, the waveform's peaks gathered on the same pass, encoded to AAC by WebCodecs' AudioEncoder. No edit list is written — YouTube's recommended settings warn that a video with one might not get processed correctly — so the encoder's lead-in stays at the start, and the picture's last frame is shortened so both tracks end together.
- Picture
- H.264, 1280×720, 4:2:0, High / Main / Baseline
- Frame rate
- 1 per second; a keyframe every 10 s
- Sound
- AAC-LC, 128 / 192 / 256 kbit/s, the project's rate
- Layout
- moov first, sound then picture, no edit list
- Shows
- Name, length and waveform — or your image
- Measured
- 10 min → 13 MB in about 18 s (Chrome, Mac)
- Free
- The mix as MP3 or WAV, up to 256 MB
New to the format? What an .aup4 file is, table by table — and how it differs from .aup3.
Sources
Where the facts on this page were checked. Audacity's code is cited at the tagged release it was read from.
- YouTube Help: recommended upload encoding settings — MP4 container with the moov atom at the front and no edit lists; H.264 video, High profile, 4:2:0; AAC-LC (or Opus) stereo sound at 48 kHz; common frame rates 24–60 with other frame rates also acceptable.
- WebCodecs, W3C — VideoEncoder and AudioEncoder, isConfigSupported (how the page asks the browser before offering MP4), encoded chunks with their decoder configuration.
- AVC (H.264) WebCodecs Registration, W3C — The avc format: a description that is an AVCDecoderConfigurationRecord (ISO/IEC 14496-15, 5.3.3.1) and a bitstream of length-prefixed NAL units, which is what the avcC box and the samples hold.
- Audacity Support: saving and exporting projects — Audacity exports a project into an audio file with File → Export Audio (MP3, WAV, OGG and, with FFmpeg, more audio formats).
Converting this file
Q. Can I upload the MP4 to YouTube?
It is made the way YouTube's recommended upload encoding settings describe: an MP4 container with its index (the moov box) at the front of the file, no edit lists, H.264 video in 4:2:0 — High profile where the browser's encoder offers it — and AAC-LC sound in stereo. Those settings list 48 kHz as the recommended sample rate; the sound here keeps the project's own rate unless you pick another under Options. They name 24 to 60 frames per second as common and say other frame rates are also acceptable; this video has one frame a second, because the picture never changes.
Q. What does the picture show?
By default the project's name, its length and the waveform of the mix, drawn on a dark background at 1280×720. Choose Use my image to show a picture of your own instead — PNG, JPEG, WebP or the first frame of a GIF — fitted whole and centred. It is one still picture for the whole length: no moving waveform, no captions.
Q. Why one frame a second?
The picture never changes, so more frames would only add encoding time: every frame goes through the encoder again. At one frame a second, with a keyframe every 10 seconds so a player can seek, the waveform picture took about 19 kbit/s. A 10-minute test project came out at 13 MB and exported in about 18 seconds in Chrome on a Mac.
Q. Is the sound the same as the MP3 or WAV export?
It is the same mix — clip gains, envelopes, track volume and pan, and with Pro the built-in realtime effects — encoded as AAC at 128, 192 or 256 kbit/s by the same encoder as the M4A export. It starts after the encoder's lead-in (2,112 samples with Apple's encoder, about 48 ms at 44.1 kHz): the M4A file trims that with an edit list, but YouTube's settings ask for none, so the video keeps it, and the picture's last frame is cut to end with the sound.
Q. Which browsers can make the MP4?
Ones whose WebCodecs offer both an H.264 video encoder and an AAC audio encoder — Chrome and Edge have both. The page asks the browser before it offers MP4; where either encoder is missing the option shows “not in this browser”, and MP3, WAV and FLAC still work there.
Q. Can each track, clip or labelled part be its own video?
Yes. With the scope set to every track, every clip, or split at labels, each file is an MP4 of its own and its picture shows that file's own name — the track's, the clip's or the label's.
Free to open, play and export the stereo mix for projects up to 256 MB; larger projects still open and play free, and downgrading to .aup3 is free up to the same size. Recovery, per-track stems, and exports or downgrades above that size are a one-time $19 license — no subscription, no recurring fees.
Every job an Audacity project needs
Same local-first engine, one page per task.