Can Audio Speed Slow Down ever speed a file up?

No. The slider runs from 0.5x to 1.0x and nothing goes above 1.00x, which returns the audio essentially untouched. Speeding up is a separate job handled by the Audio Speed Changer, and the slowdown floor is capped at half speed because both algorithms start to sound obviously processed beyond that point.

What is the difference between Tape and Preserve pitch?

Tape mode resamples the waveform, so lowering the speed lowers the pitch by the same factor; a voice gets deeper as the file gets longer. Preserve pitch mode time-stretches the audio so the duration grows while the pitch stays where it was, which suits music and pitch-matching practice but can add a faint warbling quality on dense material.

Why is the output always a WAV file?

The browser decoder hands the tool raw PCM samples, and re-encoding to a compressed format would mean bundling an encoder for every possible input type. Writing uncompressed 16-bit WAV at the source sample rate keeps the slowed copy faithful to exactly what was decoded. Convert the WAV afterwards if the size matters.

How much longer will my file be at each setting?

Divide the original duration by the multiplier. A three-minute clip becomes four minutes at 0.75x and six minutes at 0.5x. The output duration readout next to the preview buttons confirms the exact new length before you download, so you can check the result at a glance.

Will slowing a recording down make speech easier to understand?

As a rule yes, up to a point. Slowing to about 0.75x gives listeners more time to process each word without the sound turning unnatural. Past that, tape mode drops the pitch far enough that some consonants blur, and preserve pitch mode starts to smear transients, so 0.5x is best saved for short passages you are studying closely.

Audio Speed Slow Down

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Audio Speed Changer

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Time Stretcher

Stretch or compress audio duration

Playback Speed Calculator

Calculate speed change ratios

Audio Speed Slow Down replays a recording at a lower rate so difficult speech is easier to follow, stretching the file to at most twice its original length. The control range is deliberately one-sided: you can slow audio down to anywhere between 0.5x and 1.0x, but never speed it up.

What is Audio Speed Slow Down?

This tool reads a file into raw samples, rebuilds it at a slower playback rate, and hands back a WAV you can preview in place and then download. Upload anything the browser can decode — MP3, WAV, FLAC, M4A, OGG, AAC, AIFF, WMA or Opus — and the drop panel reports the decoded sample rate, channel count and duration before you change a single setting. The brief is narrow on purpose: slow down audio that is already recorded, by one fixed multiplier, and keep the result as faithful to the source as the algorithm allows. The speed control only ever moves downward, from 1.0x at the top to a 0.5x floor, and the label beside the slider converts the multiplier into the more intuitive slower percentage. The default sits at 0.75x, which is roughly where speech is noticeably slower but still natural.

The tool exposes a small, deliberately limited set of controls:

Speed multiplier from 0.5x to 1.0x in 0.05x steps.
Preset buttons for 0.5x, 0.6x, 0.7x, 0.8x and 0.9x.
Tape mode, which resamples linearly and lets pitch fall with the speed.
Preserve pitch mode, which time-stretches the audio and holds the original pitch.
WAV output at the source sample rate, named after the input with a slowed-0.75x style suffix.
Preview original and Preview edited players for an immediate A/B comparison.

Tape mode calls a linear resampler: each output sample is interpolated between two neighbouring input samples read at a position that advances by the speed factor, so the waveform is replayed more slowly and its pitch drops in step, exactly as if you had slowed a tape reel by hand. Preserve pitch mode runs an overlap-add time-stretch instead. The signal is sliced into 2048-sample grains windowed with a Hann curve and taken every 512 samples; each grain is written back at a synthesis hop scaled by the stretch ratio, and a correlation search slides every grain up to a few hundred samples either way so its onset lines up with what has already been written, before the overlapping windows are normalised. That holds the pitch steady while the timeline expands, at the cost of a faint smearing around sharp transients.

What it will not do matters just as much:

It cannot speed audio up; 1.00x returns the file essentially unchanged and nothing goes above it.
Output is always 16-bit PCM WAV, so a slowed MP3 becomes a lossless file many times the size of the original.
The whole file must decode into memory at once, so there is no streaming path for very long recordings.
Tape mode lowers pitch, so voices and instruments sound progressively deeper as the slowdown increases.
Preserve pitch mode can add a slight warbling or phasing artefact around percussive attacks.
You cannot slow a single section; the multiplier applies to the entire file from start to finish.

Reach for tape mode when the material is spoken word and a natural drop in pitch is acceptable, because it is the simpler and cleaner of the two algorithms and the one tuned for speech comprehension. Choose preserve pitch when the recording is musical, when you are learning a part by ear, or when a lower key would make the result hard to follow. For study and transcription work 0.75x is the usual starting point, with 0.5x reserved for the hardest passages where clarity beats naturalness.

How to use Audio Speed Slow Down

Drop an audio file onto the upload panel, or click it to browse; the panel then shows the decoded sample rate, channel count and duration.
Set the speed with the slider between 0.5x and 1.0x, or tap a preset; the label shows both the multiplier and the matching slower percentage.
Pick a mode — Tape for the clearest speech with a natural pitch drop, or Preserve pitch for musical material — then click Process.
Compare Preview original against Preview edited, then use Download to save the WAV, named after your file with a slowed-0.75x suffix.

When to use Audio Speed Slow Down vs related tools

Audio Speed Slow Down is the comprehension-first member of the speed family: it only ever slows a file down and uses the simplest, cleanest algorithms to do it. When you need the full range, speeding up as well as slowing with independent pitch control and finer ratios, use Audio Speed Changer instead, which handles everything from quick podcast skimming to slowed-down study playback in one place. If your goal is the tempo of a musical passage rather than the playback rate of a whole file, Tempo Changer and Time Stretcher change duration while holding pitch fixed. And to work out the exact ratio you want before you touch any audio, Playback Speed Calculator converts a target duration into the multiplier you need.

Privacy & Security

This tool runs entirely in your browser — no data ever leaves your device. There is no server round-trip, no upload, no logging, and no account required. Your input is processed locally using client-side JavaScript and is never stored, transmitted, or accessible to anyone else. When you close the tab, everything disappears.