How to compress audio via bitrate reduction — free tool
- Step 1Decide: bitrate vs. exact size — If you want a consistent quality (e.g. everything at 128 kbps), this tool is right. If you need an exact MB target, use audio-compressor instead.
- Step 2Open the bitrate changer — Open the bitrate-changer. FFmpeg 8.1 loads into the page; nothing installs.
- Step 3Drop the file to compress — Drag in MP3, WAV, FLAC, M4A, OGG, Opus, or a video. Output is always MP3. Free tier: 50 MB / 30 min.
- Step 4Pick the compression level (bitrate) — Lower bitrate = more compression. 192 kbps for general use, 128 kbps for stronger shrink, 64 kbps for voice. 320/256 kbps for light compression.
- Step 5Run the compression — FFmpeg re-encodes at the fixed CBR with
libmp3lame -b:a. The size that results is bitrate times duration. - Step 6Download and check consistency — Download the MP3. If you are batching, apply the same bitrate to every file so the whole set lands at the same quality.
Bitrate compression vs. size-targeting
Two different ways to shrink audio. This tool is the left column; audio-compressor is the right.
| Aspect | Bitrate compression (this tool) | Size-targeting (audio-compressor) |
|---|---|---|
| You choose | The bitrate (quality level) | The target file size in MB |
| The tool computes | Nothing — size = bitrate × duration | The bitrate needed to hit the size |
| Best when | Consistent quality across files | A hard size cap (e.g. under 8 MB) |
| Output | MP3 at fixed CBR | Size-targeted encode |
| Predictable size? | Yes, from the cheat sheet | Yes, that is the whole point |
Compression strength by bitrate
Lower bitrate means more compression and smaller files at the cost of quality. Per-minute sizes are approximate CBR MP3.
| Bitrate | Relative size | Per minute | Compression character |
|---|---|---|---|
| 320 kbps | 100% (baseline) | ~2.4 MB | Light — near-transparent for most ears |
| 256 kbps | ~80% | ~1.9 MB | Light — minimal audible loss |
| 192 kbps | ~60% | ~1.4 MB | Moderate — strong default for music |
| 128 kbps | ~40% | ~0.96 MB | Strong — common streaming floor |
| 64 kbps | ~20% | ~0.48 MB | Aggressive — voice only |
Cookbook
Compression by bitrate, with the resulting sizes. When you need an exact MB cap instead, the last example points to the right tool.
Normalise a music library to 192 kbps
A folder of mixed-bitrate MP3s (some 320, some 256) compressed to a single 192 kbps standard for consistent quality and size.
Inputs: mixed bitrates (320k, 256k, ...) Target: 192 kbps for all Result: every track lands at ~1.4 MB/min, uniform quality Tip: Pro tier batches up to 10 files at once
Strong shrink of a 320 kbps album track
A 5-minute 320 kbps track compressed to 128 kbps for big space savings while staying listenable.
Input: track.mp3 320 kbps 5:00 ~12 MB Target: 128 kbps Output: track.mp3 128 kbps 5:00 ~4.8 MB (~40%)
Aggressive voice compression at 64 kbps
A spoken-word file compressed hard for distribution where size matters most.
Input: talk.mp3 192 kbps 30:00 ~52 MB Target: 64 kbps · voice Output: talk.mp3 64 kbps 30:00 ~14 MB
Light compression that keeps quality high
When you only need a modest reduction, 256 kbps barely touches perceived quality.
Input: song.flac ~900 kbps 4:00 ~27 MB Target: 256 kbps Output: song.mp3 256 kbps 4:00 ~7.7 MB
When you need an exact file size
Bitrate compression cannot guarantee 'under 8 MB' for files of different lengths. Use the size-targeting tool for that.
Goal: every clip under 8 MB regardless of length
This tool: fixes bitrate, not size -> long clips may exceed 8 MB
Use instead: [audio-compressor](/audio-tools/audio-compressor)
(enter 8 MB target; it computes the bitrate)Edge cases and what actually happens
Expecting to enter a file size
Wrong toolThis tool compresses by bitrate, not by target size. For an exact MB goal use audio-compressor, which computes the bitrate to hit your size.
Wanted 96 or 160 kbps
By designOnly 320, 256, 192, 128, and 64 kbps are available. Pick the nearest step; intermediate bitrates are not offered.
Compressing an already-128 kbps file to 128 kbps
ExpectedRe-encoding at the same bitrate adds another lossy generation with no size benefit. Skip the step if the file is already at your target bitrate.
Strong compression makes music sound harsh
Expected64 kbps is voice-tuned; music at 64 kbps shows clear artefacts. For music, 128 kbps is the practical floor.
File too large for the free tier
Tier limitFree caps at 50 MB / 30 min. Split or trim long files, or upgrade to Pro (200 MB / 120 min) for bigger inputs and 10-file batches.
Batching files of different lengths to one size
By designA fixed bitrate gives different files different sizes. If a uniform file size is the goal, use the size-targeting compressor per file.
Need VBR for better quality-per-byte
Not supportedThe tool only writes CBR. VBR's efficiency advantage is not available here.
Output must stay lossless
Not supportedCompression here is lossy MP3. To stay lossless while reducing size, re-encode FLAC at a higher compression level with a FLAC converter instead.
Tags preserved through compression
PreservedID3 tags and cover art carry across (-map_metadata 0), so a batch-compressed library still displays artist, title, and artwork.
Frequently asked questions
What does 'compress by bitrate' mean?
You choose a lower constant bitrate and the file is re-encoded at that rate. The resulting size follows automatically (bitrate × duration). You control quality; size is the consequence.
How is this different from targeting a file size?
This tool fixes the bitrate. To hit an exact size in MB, use audio-compressor, which works backward from your size goal.
Which bitrates can I compress to?
320, 256, 192 (default), 128, and 64 kbps, all constant bitrate.
Is the output always MP3?
Yes. There is no output-format selector on this tool.
Does compression upload my file?
No. FFmpeg 8.1 WASM compresses locally in your browser; nothing is uploaded.
How much smaller will the file be?
Predictably: 320 to 128 kbps is roughly 40% of the original; 320 to 64 kbps is roughly 20%. See the strength table above.
Can I compress many files at once?
Free tier is one file per run. Pro allows up to 10 files per run at the same bitrate.
Will compression keep my tags?
Yes, ID3 tags and cover art are preserved through the re-encode.
Is there a VBR compression mode?
No. The tool only produces CBR output.
What is the lowest sensible bitrate for music?
128 kbps. Below that, artefacts become audible. 64 kbps is for voice only.
What are the size limits?
Free: 50 MB / 30 min / 1 file. Pro: 200 MB / 120 min / 10 files. Pro-media and Developer: up to 100 GB, no duration cap.
Can I compress a FLAC or WAV this way?
Yes, but the result is a lossy MP3. To keep losslessness while shrinking, re-encode FLAC at a higher compression level with a FLAC converter instead.
Privacy first
Every JAD Audio tool runs entirely in your browser via FFmpeg (WebAssembly) and RNNoise. Your audio files never leave your device — verified by zero outbound network requests during processing.