Convert .aup3 to MP3 online
An .aup3 file is an Audacity 3 project, not an audio file — which is why players, converters and phones all refuse it. Drop it here to hear it and download an MP3, with nothing uploaded.
Why can't I play an .aup3 file, and how do I turn it into an MP3?
An .aup3 file is an Audacity 3 project: an SQLite database holding the audio as thousands of separate blocks plus a document describing where each clip sits. There is no continuous audio stream inside for a player to read, which is why VLC, a phone and a generic converter all fail. Drop it on this page and the browser reconstructs the timeline from those blocks and encodes an MP3 locally, with nothing uploaded.
Drop the .aup3 file — it is read on your machine.
See the track list and play the mix.
Pick a bitrate and download the MP3.
Pro adds per-track and per-clip exports, and exports of projects larger than 256 MB.
Convert .aup3 to MP3 online
This is the most common way people meet the problem: a recording was made in Audacity, saved, and the .aup3 file is the only thing left. Emailing it to someone gets "I can't open this", and every converter that turns up in a search either identifies the file and stops, or advertises desktop software that cannot read the format either. The engine on this page is the same one used for Audacity 4 projects — Audacity 3 and 4 store audio identically, so an .aup3 opens here just as well.
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.
Why an .aup3 file will not play
Audacity 3.0 replaced the old .aup-plus-folder arrangement with a single SQLite database. Inside, the `sampleblocks` table holds the audio in immutable blocks of up to about a megabyte, each around five seconds of mono audio at default settings, and the `project` table holds a binary-encoded XML document describing tracks, clips and which blocks each clip is built from.
That means the file contains no playable stream. Even the audio inside is split across hundreds or thousands of rows, in a channel-per-track layout with trims and envelopes applied only at playback. Reconstructing it takes a reader that understands the document, which is what this page implements. The rebuilt mix is rounded to 16-bit for the encoder — the JavaScript LAME port takes integer input, where Audacity's own MP3 export feeds LAME 32-bit float — and then encoded at the bitrate you pick.
The design has one useful consequence: because blocks are never rewritten, the audio in a project usually survives damage that makes Audacity refuse to open it. That is the basis of the recovery page.
- Introduced
- Audacity 3.0 (2021), replacing .aup plus a _data folder
- Container
- SQLite 3 database with an Audacity application id
- Blocks
- Up to ~1 MB each, about five seconds of mono audio
- Read by Audacity 4?
- Yes — opened and converted to .aup4, one way
- Read by media players?
- No — there is no audio stream to read
- Older .aup files
- Not supported by Audacity 4; convert with Audacity 3.7 first
- Encoder input
- 16-bit integers, rounded without dither; Audacity's export feeds LAME 32-bit float
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.
- ExportMP3.cpp, Audacity 3.7.9 — Audacity's MP3 export mixes to floatSample and calls lame_encode_buffer_interleaved_ieee_float (or lame_encode_buffer_ieee_float for mono), so LAME receives 32-bit float samples rather than 16-bit integers.
- Dither.cpp, Audacity 3.7.9 — 16-bit conversion uses one constant both ways, CONVERT_DIV16 = 1 << 15: an integer is read as n / 32768, and a float is stored as lrintf(f × 32768) clipped to −32768…32767. The two dither settings default to none (real-time) and shaped (high-quality).
Converting this file
Q. Is this the same as opening it in Audacity?
For getting the audio out, yes — the same blocks, positions, trims and envelopes are used. Audacity additionally renders realtime effects, which this page does not, so a project that leans on plugin effects should be exported from Audacity.
Q. Does my recording really stay private?
Yes. The project is opened with the browser's File API and parsed in a Web Worker on your own machine. Nothing about it is sent anywhere — you can disconnect from the network after the page loads and keep working.
Q. My project is several gigabytes. Will it work?
Any project the browser tab can hold opens and plays; exporting one larger than 256 MB is part of Pro. There is no streaming reader: the whole project is read into the tab's memory — the file bytes plus SQLite's own copy, so roughly twice the file size — with the rendered mix on top. A project of a few gigabytes therefore needs a 64-bit browser with that much memory to spare, and one the browser cannot hold fails at the open step with a message saying so; nothing opens partially.
Q. What about an old .aup file from Audacity 2?
Those are different: a small XML file plus a separate _data folder holding the audio, so the .aup file alone contains no audio at all. Open it in Audacity 3.7 and save it as .aup3 first — Audacity 4 cannot import them either.
Free to open, play and export the stereo mix for projects up to 256 MB; larger projects still open and play free. Recovery, downgrading, per-track stems and exports 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.