What does an audio compressor do?
An audio compressor turns the loud moments down so the quiet ones can be turned up. The result is a sound that is more even, more upfront and easier to hear: a vocal that stays steady instead of jumping out on some words and vanishing on others, a podcast that does not need the volume knob every two minutes, drums that hit with the same weight every time.
This is loudness compression, not file compression. It changes how the audio sounds, not how many megabytes it takes up. If what you want is a smaller file, the Audio Converter does that: pick MP3 and a lower bitrate.
The controls here follow a classic studio design. There is no threshold knob. Instead, Input pushes the sound into the compressor (turn it up for more squash) and Output sets the level coming back out. Pick a ratio with the buttons, set how quickly it grabs (Attack) and lets go (Release), and watch the needle swing to the left as it works.
How to compress audio online
- 1
Upload your file
Drag an audio file onto the box above, or click to browse. MP3, WAV, FLAC, M4A, AAC, OGG, OPUS and WebM all work.
- 2
Press play and turn the knobs
Pick a preset or start from Clean. Turn Input up until the needle moves, then bring Output down to taste. Everything changes live while the file plays, and the Original tab lets you check what you started with.
- 3
Compress and download
Press Compress to render the whole file with exactly what you heard, then save it as MP3 or lossless WAV.
What people compress audio for
Compression is on almost every recording you have ever heard. Here is where it earns its keep.
Vocals
A singer moves closer to and further from the mic and sings some notes harder than others. The Vocal preset (8:1, medium attack) holds the level steady so every word sits in the mix.
Podcasts and voice-overs
Speech has big swings between a laugh and a mumble. Compress it and listeners stop reaching for the volume. Start with Vocal, then ease Output until it matches your other episodes.
Drums
The Drums preset uses the ALL setting: the attack lags a little so the first crack of each hit gets through, then everything behind it is clamped down. That is the punch and grit of countless records.
Whole mixes
A gentle 4:1 with a slow attack, the Glue preset, makes the parts of a song feel like one performance. For a loudness-normalised master with EQ as well, use the Mastering tool instead.
Phone recordings
Voice memos and video audio are quiet and uneven. A few dB of Input and a little Output make them clear and consistent without touching anything else.
What each control does
- Input
- How hard the sound is pushed into the compressor. The threshold is fixed, so more Input means more compression and a louder result. This is the main knob.
- Output
- The level on the way out. There is no automatic make-up gain here: after turning Input up, pull Output down until the Compressed tab is as loud as the Original tab, and the comparison is fair.
- Ratio
- How much the loud parts are held back. 4:1 is gentle glue, 8:1 is the usual vocal choice, 12:1 is firm, 20:1 is close to limiting. ALL is every button pressed at once: a hard knee and a lagging attack, the aggressive sound drums love.
- Attack
- How fast the compressor grabs a loud moment. Numbered 1 to 7 with 7 the fastest (20 microseconds). A slower attack lets the start of each hit through; a faster one clamps everything.
- Release
- How fast it lets go afterwards, from just over a second at 1 down to 50 milliseconds at 7. Faster release sounds louder and more energetic; slower sounds smoother.
- The needle
- The gain-reduction meter shows how many dB the compressor is taking off right now. Resting at the right means nothing is happening. Most of the time 3 to 6 dB on the loud parts is plenty.
Compressor vs limiter vs normalizer
Compressor
Turns loud moments down by a ratio, with an attack and release you can hear. Shapes the feel of the sound. This tool.
Limiter
A compressor with a very high ratio and a fast attack: a ceiling that nothing crosses. Use 20:1 here with Attack on 7 for something close, or the Mastering tool for a true peak-safe limiter.
Normalizer
Turns the whole file up or down by one fixed amount so its loudest point hits a target. It changes nothing about the balance between loud and quiet parts. Our Mastering tool normalises to a loudness target as its last step.
Frequently asked questions
Is this audio compressor free?
Yes, completely. There is no sign up, no watermark, no file limit and no paid tier. The tool runs inside your browser, so there is no server cost to pass on to you.
Does this make my audio file smaller?
No. This compressor evens out loudness; the file stays the same length and the download is a full-quality MP3 or WAV. To shrink a file, use our Audio Converter and choose MP3 with a lower bitrate, such as 128 kbps.
Is my audio uploaded anywhere?
No. Your file is read, compressed and rendered by your own browser and never leaves your device. You can disconnect from the internet after the page loads and the tool still works.
What settings should I use for a vocal or a podcast?
Start with the Vocal preset: 8:1, Input +8, Output -4, Attack 3, Release 5. Play the file and watch the needle. If it barely moves, add Input; if it is pinned past 10 dB on every word, take some away. Then adjust Output so the Compressed tab is about as loud as the Original tab.
Why is the compressed version louder than the original?
Because this design has no automatic make-up gain. Turning Input up makes the whole thing louder as well as more compressed, exactly as the classic hardware does, and you balance it yourself with Output. Match the two tabs by ear before deciding whether you like the compression itself.
What does the ALL button do?
It is the famous all-buttons-in trick: on the original hardware, pressing every ratio button at once produced a mode nobody designed, with a hard knee, a lagging attack and a crunchy, grabby sound. Drums love it. Try the Drums preset to hear it.
Keep going with your audio
Compressed your track? These tools pair well with it.