fre:ac — Free Audio Converter Setup Guide for FLAC to MP3

fre:ac (short for “free audio converter”) is a GPL-licensed desktop application that converts between audio formats: FLAC, WAV, AAC, Ogg Vorbis, WMA, and MP3. It can also rip audio CDs. The project has been active since 2001 and is maintained by Robert Kausch on GitHub.

For FLAC to MP3 specifically, fre:ac uses the LAME encoder — the same open-source MP3 encoder used by virtually every other converter, including the browser-based tool on this site. At the same bitrate settings, the output files are identical regardless of which front-end produced them. The software comparison covers why this is the case in more detail.

What fre:ac brings to the table is not better encoding — it is better automation. It will take a nested folder tree of thousands of files, encode them in parallel across all your CPU cores, mirror the directory structure on the output side, and copy every tag and embedded image into the resulting MP3s. No other free tool does all of that as reliably.

Download fre:ac from freac.org. Avoid third-party download sites — some wrap the installer in adware bundles that the project itself does not ship.

Windows

Two options: the standard installer (.exe) or a portable ZIP. The portable build runs from any folder — useful on machines where you cannot run installers, or when you want fre:ac on a USB stick. Both contain the same program.

macOS

Download the .dmg, open it, and drag fre:ac into Applications. On Apple Silicon Macs, fre:ac runs natively — no Rosetta required since version 1.1.7.

Linux

Available as a Snap, Flatpak, or AppImage. The Snap installs with sudo snap install freac and auto-updates. The AppImage needs no installation at all — download, make executable, run.

fre:ac works out of the box, but the defaults are not ideal for MP3 output. Spend two minutes in settings once and every future conversion uses them automatically.

Step 1 — Select the LAME MP3 encoder

Open Options → General settings → Encoder and pick LAME MP3 Encoder from the dropdown. This tells fre:ac that every file it encodes should produce an MP3.

Step 2 — Set the bitrate

Click the gear icon next to the encoder dropdown to open LAME settings. Two options worth considering:

• CBR 320 kbps — maximum fixed bitrate. Every second of audio uses 320 kilobits, producing files of about 2.4 MB per minute. The safest choice if you never want to wonder whether quality was compromised.
• VBR preset “V0” — LAME allocates bits dynamically, averaging around 245 kbps. Transparent in ABX tests for virtually all material, and about 25% smaller than CBR 320. If you care more about the audible difference between FLAC and MP3, this is where to start reading.

Avoid bitrates below 192 kbps unless you are targeting a very storage-constrained device. The file size savings are small; the audible cost is not.

Step 3 — Set the output folder and filename pattern

Under Options → General settings → Output, pick a destination folder. The default filename pattern is <artist> - <title>, which works for single albums. For a whole library, change it to:

<directory>/<filename>

This mirrors the original folder structure — your carefully organised Artist/Album/Track layout survives the conversion intact.

Step 4 — Enable parallel encoding

Under Options → General settings → Resources, set the number of parallel conversions to match your CPU core count (or leave it on “automatic”). On an 8-core machine this encodes eight files simultaneously, cutting total conversion time roughly eightfold compared to single-threaded operation.

With settings done, the actual conversion is three steps:

1. Add files. Drag your top-level music folder into the fre:ac window, or use File → Add folder. fre:ac walks every subfolder and queues every FLAC file it finds. Non-FLAC files are ignored.
2. Review the queue. The file list shows the artist, title, album, and duration read from each file's tags. Spot-check a few entries to make sure tags look correct — fre:ac will copy them as-is into the MP3s.
3. Press encode. Click the play button (or Encode → Start encoding). fre:ac shows a progress bar per file and an overall completion estimate. On modern hardware, expect roughly 20–50× real-time speed per core — a 4-minute track encodes in under a second.

When it finishes, the output folder contains MP3 files with the same directory layout, filenames, and metadata as the originals. Play a few to confirm, then copy them to wherever they need to go — phone, car USB, portable player.

• Cover art missing after conversion. Make sure the artwork is embedded in the FLAC file, not a separate folder.jpg. fre:ac copies embedded art into ID3v2 but does not look for loose image files.
• Characters replaced with underscores in filenames. fre:ac sanitises filenames for the target filesystem. On Windows, characters like : ? * " are not allowed in paths and get replaced. The tags inside the file are unaffected.
• Encoding seems slow. Check that parallel encoding is enabled (Resources tab). Also, VBR modes are slightly slower than CBR because LAME does more analysis per frame — but “slow” still means faster than real time on any machine from the last decade.
• Want to convert only new files. fre:ac does not have a built-in “skip existing” option. The workaround: add all files, then manually remove those that already have MP3 counterparts, or use a script to pre-filter. For ongoing library maintenance, an ffmpeg loop with a file-existence check is more practical.

fre:ac is the right tool when the job is large: hundreds or thousands of FLAC files, nested folder structures you want preserved, and enough files that parallel encoding matters. It handles that case better than any other free option.

It is not the right tool for every situation:

• A few albums before a trip. A browser-based converter finishes the job faster than the fre:ac download. Nothing to install, nothing to configure.
• Mac users who also rip CDs or work with cue sheets. XLD splits a FLAC-plus-cue image into tagged per-track MP3s in one pass — something fre:ac cannot do.
• Automation on a server or NAS. ffmpeg in a shell script is simpler to schedule and has no GUI dependency. The how-to guide has the one-liner.
• Already using foobar2000 as a player. Its built-in converter avoids adding another application, though it needs the separate Encoder Pack for MP3 output.

For a side-by-side feature comparison of all seven options, see the FLAC to MP3 conversion software roundup.

MP3 is a lossy format — every conversion discards audio data that cannot be recovered. The MP3 files fre:ac produces are disposable copies for devices and situations that do not support FLAC. The lossless originals are the archive you re-encode from if you ever need a different format or bitrate. Converting MP3 back to FLAC makes the file bigger without restoring anything — it is a one-way trip.