When Audacity crashes, hangs, or crawls while exporting an MP3, the manual points at one cause before any other: your Project Rate is very different from the sample rate of the track on screen, so Audacity has to resample while it encodes. Reinstalling, switching bit rate modes, or blaming LAME all come after that check.
What this error actually means
Audacity's FAQ on MP3 export problems states the mechanism in one sentence: "If Audacity crashes or hangs when exporting MP3s, or the export takes a long time to process, the usual reason is that your chosen Project Rate in Audio Settings Preferences is very different from the sample rate of the audio track on the screen (as shown in Hz on the Track Control Panel above the mute/solo buttons). As a result, resampling has to be done while exporting, which can create problems on long tracks."
Three parts of that are worth separating, because each one tells you something different:
- There are two sample rates, not one. The Project Rate lives in Audio Settings Preferences; the track's own rate is displayed in Hz on the Track Control Panel, above the mute and solo buttons. A crash-prone export is one where those numbers disagree.
- The conversion is happening during the export. Resampling is not a step you ran earlier and forgot about — it is being performed at the same moment the file is being encoded and written.
- The qualifier is "on long tracks." That is the manual's own scope for when this "can create problems," and it matches what people report: a thirty-second clip exports fine, an hour-long recording from the same project does not.
The reason this catches people who never touched a sample rate setting is spelled out on the same page: "Make a rule to check this before you export, because importing a file of some other sample rate may change the Project Rate to that rate." So a voice memo or an old clip recorded at some other rate can drag the whole project's rate with it at import time, silently, and the bill only arrives at export.
Audacity's Importing Audio page also lists what the Project Rate governs, and the list includes the line that matters here: "when the audio is exported, it will be exported as a 44100 Hz file." That consequence is missing from the otherwise identical box on the Audio Settings Preferences page, which lists only four — so depending on which page you read, you may never connect Project Rate to exporting at all.
The fastest fix: resample before the export, not during it
The FAQ gives the sequence directly: "Try resampling the track to your chosen Project Rate before exporting as MP3. To do this, select all the track by clicking in the Track Control Panel, then Tracks > Mix > Mix and Render."
In order:
- Read the track's rate in Hz on the Track Control Panel, above the mute and solo buttons.
- Set your Project Rate in Audio Settings Preferences. For MP3 specifically, the manual's stated position is blunt: "The safest solution is to always set your Project Rate to 44100 Hz." The MP3 Export Options dialog offers only three sample rates anyway — 32000 Hz, 44100 Hz (the default) and 48000 Hz.
- Select the whole track by clicking in the Track Control Panel, then run
Tracks > Mix > Mix and Render. This is the official pre-step, and it moves the resampling work out of the export. - Export with
File > Export Audio, choosing MP3 from the Format dropdown.
One caveat on step 3 that the Advanced Mixing Options page makes explicit: "the Tracks > Mix > Mix and Render and Tracks > Mix > Mix and Render to New Track commands only mix down to mono or stereo." If you were counting on a multi-channel export, Mix and Render is not the route.
Try it right here
Runs in your browser. Your file is not uploaded anywhere.
There is also a way to sidestep the encode entirely: export to WAV from Audacity, then convert that WAV to MP3 above. The converter runs inside your browser tab — the audio is read from disk and encoded locally, nothing is uploaded. Audacity's MP3 page recommends this shape of workflow for a separate reason anyway: "never do production work in MP3, instead work with a lossless format such as WAV, AIFF or FLAC and for final use then export to MP3."
Other causes, in order of likelihood
Your virus scanner is inspecting the file as it is written. The same FAQ names this outright: "if you have a virus scanner set to scan all created files, this will slow the process of writing the exported file considerably. The higher the bit rate you export at, the larger the file will be, so giving a greater time penalty if you enable virus scanning." That last clause is a lever you control. The Excessive preset is "a constant bit rate of 320 kbps, which is equivalent to 2.4 MB per minute," while for spoken word the manual says "96 kbps CBR mono can give excellent quality for voice" — a much smaller file for the scanner to chew through.
The disk is full or not writable. Audacity's Disk full page lists Exporting among the operations that trigger it, alongside Recording, Saving a project, Importing, Applying effects and Editing, and describes the message as "telling you that the disk you are using is full, or that the disk or file that you are trying to write to is write-protected." For scale: "one hour of stereo recording at default settings (44.1kHz, 32-bit) occupies approximately 1.2 GB of disk space." Audacity warns you "on start up or when using File > New to create a new project if you have 100 MB or less space in the temporary folder for recording or editing." When freeing space, the manual is specific: "Do not delete the AUP3, WAL or (Windows only) SHM files for your project."
You are exporting onto a FAT or FAT32 drive. Those drives cap any single file at 4GB, and that cap applies to exports. For MP3 it is usually a red herring — "for compressed formats such as MP3 and AAC the maximum size will be much larger and unlikely to be an issue for most, if not all, users." If you do hit it, "freeing up space will not work and you will need to Export to a non-FAT formatted drive."
The export ends with "Unable to export" and a code. That page describes itself as the "landing page for esoteric Export failure messages" and sends you to the disk check first: "Some of these errors may have an underlying cause of disk full." Otherwise it asks you to "report the error code (here 'OGG:355') on the Audacity Forum."
The export completes but the MP3 is broken. That is a different failure with a different cause — see why an exported MP3 will not play.
How to tell it worked
Compare the two numbers again before you re-export: the rate on the Track Control Panel and the Project Rate in Audio Settings Preferences should now match, which means nothing has to be resampled mid-export. Then sanity-check the finished file's size. At 128 kbps constant bit rate the manual says you get "about 1 MB per minute of mono or stereo audio"; at the Excessive preset it is 2.4 MB per minute. Audacity's default is neither of those — it is "170 - 210 kbps VBR (preset 'Standard')" — so use these as rough bearings rather than exact targets.
FAQ
Why does Audacity take so long to export an MP3? The FAQ gives two reasons on the same page: a Project Rate that is very different from the track's sample rate, which forces resampling during the export, and a virus scanner set to scan all created files, which "will slow the process of writing the exported file considerably."
What Project Rate should I use before exporting MP3? 44100 Hz. The manual calls it "the safest solution" and tells you to check it before every export, because importing a file at another sample rate may change the Project Rate to that rate. The MP3 export dialog itself offers only 32000, 44100 and 48000 Hz.
Does Mix and Render change my project? It mixes your selected tracks down. The manual states that Mix and Render and Mix and Render to New Track "only mix down to mono or stereo," so it is not a path to a multi-channel export.
Should I disable my antivirus to speed up exporting? That is your call, and not something to do lightly. The manual's own framing gives you a gentler lever: the time penalty scales with file size, so exporting voice content at a lower constant bit rate shrinks what the scanner has to process.
Do I still need to install LAME for MP3 export? Not on Windows or Mac: "the LAME library for MP3 export is built-in with Audacity for Windows and Mac. Linux users will still need to download and install the free and recommended LAME third-party encoder." Most "install LAME first" tutorials describe the old situation.
More Audacity export failures by symptom live in the fix guides, including the silence at the start of every exported MP3. If you would rather skip the encoder entirely, the browser-based WAV to MP3 converter sits alongside all Clapr tools. Behaviour above is quoted from the official Audacity Manual, checked 16 September 2026.
