Make an Audacity project file smaller
Drop a project to see what its file is carrying besides the project: pages SQLite kept after audio was deleted, audio blocks no save uses, earlier saves. Then save a compact copy without them; the original stays as it is.
Several projects? Drop or choose them together: export them all to one ZIP at once (Pro), or open them one by one free.
Why is my Audacity project file so big, and how do I shrink it?
Mostly because it holds every sample of the audio uncompressed, but often also because of space Audacity no longer uses: SQLite keeps the pages of deleted audio for reuse, and Audacity only rewrites the file without them when a project closes with at least a fifth of its audio data unused. Drop the project here to see how much of the file is that dead weight, then save a compact copy without it — the same project and audio in a smaller file, made in your browser with nothing uploaded.
Drop an .aup3 or .aup4 project (with its -wal, if one sits beside it).
Read the File size panel: free pages, audio no save uses, earlier saves, and the size a compact copy would be.
Save a compact copy: same project, same audio, a smaller file next to the original.
The report is free; saving the compact copy is part of Pro.
Make an Audacity project file smaller
An .aup3 or .aup4 file is an SQLite database, and a database does not shrink when rows are deleted: the pages go on a free list for reuse. Audacity rewrites the file without them only when a project closes with at least a fifth of its audio data unused, and a session that crashes never gets that far. The report here reads the database's own numbers, and the compact copy holds the saved project, its audio block for block, and nothing else.
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.
Where the extra size in an Audacity project comes from
Audacity sets a 64 KiB page size on the project database, puts it in WAL mode and never turns on auto_vacuum, so when audio blocks are deleted — trimmed, undone past, or left behind by a session that did not save — their pages move to SQLite's freelist. The file keeps its size and fills those pages again before it grows. The freelist count sits in the database header, and the panel multiplies it by the page size.
Audacity's own clean-up runs when a project closes: ProjectFileIO::ShouldCompact sums the bytes of the blocks the last saved state uses and of every block in the file, and only when the used share is at most 80% does Compact copy the project to a fresh file holding just those blocks. Audacity 4 calls the same code on close. Below that threshold, or after a crash, the dead weight stays. Audacity 4 also keeps the last ten saved documents in project_history; they are small, but they are not the current project.
The compact copy is written the same way Audacity's copy is: the schema statements read from the original, the saved document, the autosave copy when it decodes, and only the audio blocks those reference, one row at a time. Of project_history only the entry identical to the saved document stays; AUTOINCREMENT's counter is kept, so a block id is never reused.
- Page size
- 64 KiB (AUDACITY_PROJECT_PAGE_SIZE)
- Auto-compaction
- On close, when ≤ 80% of block data is in use
- Earlier saves
- Last 10 in project_history (Audacity 4)
- Kept
- Saved document, autosave copy, used audio, schema, header
- Left out
- Free pages, unused blocks, earlier saves
- Needs
- The whole project in this tab's memory to write the copy
- Free
- The size report, at every size
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.
- ProjectFileIO.cpp, Audacity 3.7.9 — ShouldCompact compacts only when the blocks in use are at most 80% of all block bytes (sum of each row's lengths); Compact copies the project to a new file with only those blocks; SaveCopy (Backup Project) copies with pruning.
- FileMenus.cpp, Audacity 3.7.9 — Backup Project under File → Save Project; the Compact Project command commented out over Bug 2600.
- ProjectFileManager.cpp, Audacity 3.7.9 — CompactProjectOnClose: compaction is attempted when a project closes, around the last saved tracks.
- DBConnection.cpp, Audacity 3.7.9 — page_size 65536, journal_mode WAL and wal_autocheckpoint 0 are the pragmas set; auto_vacuum is not.
- ProjectFileIO.cpp, Audacity 4.0.0 — kProjectHistoryDepth = 10 saved documents in project_history, written on every save; the same ShouldCompact threshold.
- au3project.cpp, Audacity 4.0.0 — Audacity 4 compacts the project around the last saved tracks when it closes.
- SQLite database file format — The freelist and its page count at header offset 36; freed pages are reused before the file grows.
Before you trust a recording to a website
Q. Does compacting change the audio?
No. The compact copy keeps the saved project document byte for byte and copies every audio block it uses unchanged, with the same sample format and the same summaries Audacity drew the waveform from. Only blocks that no save refers to, the free pages and the earlier saves are left out, and the original file is not touched.
Q. How much smaller will it get?
It depends on the project's history, and the File size panel shows the figure before you save anything. A project closed cleanly after little editing may have nothing to give back; one that went through long recording sessions, many deletions or a crash can carry a large share of dead weight. The audio itself does not get smaller: Audacity stores it uncompressed, so an hour of stereo at 44.1 kHz in 32-bit float is about 1.27 GB of samples either way.
Q. Can't Audacity do this itself?
Partly. Audacity compacts a project when it closes, but only when at least a fifth of the audio data is unused, and never after a crash. Its Compact Project menu item was taken out over Bug 2600 (it confused undo), and Audacity 3.x's File → Save Project → Backup Project writes a copy with only the audio in use. This page tells you first how much there is to gain, works on a machine without Audacity, and also leaves out the earlier saves an Audacity 4 project keeps.
Q. What happens to unsaved changes from a crash?
They are kept. Audacity writes an autosave copy of the project while you work and deletes it on a clean save; if one is still in the file, the session ended without saving. When it decodes, the compact copy keeps it and the audio it uses, so Audacity still offers to recover those changes. An autosave copy that no longer decodes is left out, and the panel says so.
Q. Is the compact copy still an Audacity 4 project?
Yes. It keeps the original's database schema, page size, application id and version number exactly, so the same Audacity versions open it; an .aup4 stays an .aup4 and an .aup3 stays an .aup3. To open an Audacity 4 project in Audacity 3.7 as well, use the downgrade page.
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.