Audio Speed Changer is a free, in-browser audio tool. Change the playback speed of any audio file from 0.5× to 2× while preserving pitch using FFmpeg's `atempo` filter. Perfect for speeding up podcasts, slowing down music transcription, or adjusting voice notes. Files are processed entirely in your browser. The page exposes a small surface — input, controls, output — so a first-time visitor can complete the job without reading documentation.
Behind the controls you see, standard browser APIs is doing the actual audio editing and conversion. MP3, WAV, M4A, AAC, OGG, Opus, FLAC, AIFF, and WMA are first-class formats and the engine produces a deterministic output for any given input + options combination — useful when you need to re-run a job and expect identical results.
Audio Speed Changer is a static page plus a client-side engine. The browser does the work; there is no separate backend in the loop for the actual processing. That architecture is why the tool starts immediately, why it does not depend on the load on a remote service, and why running multiple jobs in a row does not slow it down.
Anyone who works with audio editing and conversion on a casual basis — teachers recording lessons, streamers cleaning microphone tracks, students preparing oral submissions — finds Audio Speed Changer a quick way to get the result. The page loads in under a second, the controls are visible from a single screen, and the result downloads or copies in one click.
Most people land on Audio Speed Changer via a search at the moment they actually need the tool. That shapes the design: the page is a single screen with the input on one side, the controls in the middle, and the result on the other, so a first-time visitor can complete the job without reading documentation.
A practical note on limits: Audio Speed Changer accepts inputs up to 200 MB per run, and the tool processes one input at a time to keep memory usage predictable. If you ever bump into the ceiling, the cause is the size of the input.
For multi-step jobs, Audio Speed Changer sits next to Metronome, Audio Reverser, and Audio Loop. None of them depend on each other — you can use Audio Speed Changer on its own — but together they cover the common variations of the task this page exists to handle.
Audio Speed Changer keeps the control set focused. Every option on the page is there because a real workflow needs it, and the defaults aim at the most common case so a first-time user can get the right output without changing any settings.
Audio Speed Changer returns the result as `{name}-edited.{ext}`. If you are running multiple jobs, the output names will not collide as long as the input names differ. You can re-run with different settings as many times as you like; each run produces a fresh file with no caching trickery in between.
Some background on the design choices behind Audio Speed Changer: every option you see on the page is there because a real workflow needs it, and every option that is not shown has been deliberately omitted to keep the common case fast. The bias is toward minimal-but-complete.
If you also use a command-line tool for audio speed changer, Audio Speed Changer is a convenient alternative for the times you are on a different machine or helping someone who is not comfortable in a terminal. The output is a standard file in the format documented above.
A few practical tips that experienced users of Audio Speed Changer pick up over time. First, keep your default browser updated — the engine relies on standard web APIs and newer browser versions are noticeably faster than ones from a few years ago. Second, close other heavy tabs before processing a large input; the engine shares CPU and memory with whatever else is open. Third, if you re-run the same kind of job often, your last-used settings are remembered for the rest of the tab session, so subsequent runs are essentially one click.
For most failure modes, refreshing the page and re-running the job is enough — the engine has no persistent state to corrupt. If the same input fails twice in a row, the input itself is most likely the problem (a truncated file, an unexpected variant of the format, or a stream the engine does not recognise).
Open the workspace above to start using Audio Speed Changer. The engine loads on the first interaction so the page itself stays light, and once the tool is warm it processes subsequent jobs quickly. The moment the page is interactive, the tool is ready to do real work on your file.
No — the tool uses FFmpeg's atempo filter, which is a phase-vocoder time-stretching algorithm that changes the duration without changing pitch. A 1.5× sped-up podcast still sounds like the original speaker, just faster. Without atempo, doubling speed would shift everything up an octave (the chipmunk effect).
0.5× (half speed) to 2× (double speed). Beyond these limits the time-stretching algorithm starts to introduce audible artifacts. For more extreme speed changes, the tool internally chains multiple atempo filters (FFmpeg's atempo allows 0.5–2.0 per pass; we apply 2–4 passes for ratios outside that range).
Speeding up podcasts and lectures (1.25–1.75× saves significant time without losing comprehension), slowing down music for transcription or learning a difficult passage, accessibility (slowing down speech for clearer comprehension), and creative audio effects.
Time-stretching is not free — it works by shifting overlapping windows of audio, which can cause subtle "watery" or "phasey" artifacts at extreme speeds. At moderate ratios (0.75–1.5×) the quality is excellent and the artifacts are inaudible to most listeners.
Roughly real-time on a modern desktop — a 60-minute podcast at 1.5× takes about 60 seconds to process. WebAssembly is single-threaded so processing time scales linearly with file length. Mobile devices are 2–3× slower than desktops.
Apps like Overcast play the file at the new speed in real time as you listen — they never produce a new file. This tool actually re-encodes the audio so you have a permanent sped-up file you can share, upload, or use elsewhere. The processing wait is the price for that flexibility.
Server-side tools use multi-threaded native FFmpeg running on dedicated CPUs with fast disks and parallel pipelines. Our engine is FFmpeg compiled to WebAssembly, which runs single-threaded inside your browser tab and has no access to native hardware acceleration. That makes browser-based jobs typically 3–8× slower than a server. The trade-off is total privacy: your audio file is never uploaded, never logged, and never stored — closing the tab erases everything from memory immediately. For most clips up to a few minutes the wait is small, and for sensitive recordings (voice memos, drafts, confidential meetings) the privacy gain is well worth it.
No. Everything runs entirely inside your browser tab using FFmpeg compiled to WebAssembly. The file is read into local memory only, processed in the same tab, and the result is offered as a direct download. Nothing is transmitted to any server, no account is required, no analytics are tied to your file, and closing the tab discards every byte from memory.
The file picker accepts audio inputs up to about 1 GB, which is well above what mainstream "free tier" online converters allow. The real ceiling is your device — everything runs inside your browser tab, which shares memory with the rest of the page. Most podcasts, songs, and voice memos sit comfortably under that limit even on a phone. If a very large lossless WAV or FLAC ever fails, trim it first or transcode to MP3 / Opus to bring the size down before re-running the tool.
MP3, WAV, OGG (Vorbis and Opus), FLAC, M4A (AAC), AAC, Opus, AIFF, and WMA all decode reliably via FFmpeg WASM. Output formats depend on the specific tool — most editing tools default to MP3 (universal) or WAV (lossless) but expose a format picker so you can pick the one that fits your downstream player or DAW.
Recent Chrome, Edge, Firefox, Safari, and other Chromium-based browsers all work. The tool relies on WebAssembly and SharedArrayBuffer, which require the page to be served over HTTPS with the right cross-origin headers — this site is configured correctly by default. On phones the same code runs but is slower than on a desktop because mobile CPUs are weaker.
No. The tool is completely free, requires no account, attaches no watermark, applies no usage caps, and shows no popup ads on your output. Because the work happens on your own device, there is no per-user quota for us to enforce — your hardware and browser memory are the only limits. The download is the file you would get from running FFmpeg locally, nothing more, nothing less.
Most jobs finish in seconds. Speed scales with input size and with how many CPU cycles your browser tab has available — the engine runs in your browser, so it shares resources with whatever else you have open. For inputs near the 200 MB ceiling, expect anywhere from a few seconds to roughly a minute on a typical laptop. Closing other heavy tabs noticeably speeds things up.
Audio Speed Changer accepts MP3, WAV, M4A, AAC, OGG, Opus, FLAC, AIFF, and WMA. If your input is in a format that is not directly supported, convert it first using one of Favtoo's converter tools — every Favtoo converter outputs a file that is a clean input to the next tool in the chain.
Audio Speed Changer processes one input at a time by design — it keeps memory usage predictable on lower-end devices and makes results easier to verify. To handle a folder, run the tool once per file; the page stays loaded between runs and remembers your last-used settings, so the second run is essentially instant.
Failures usually fall into one of three buckets: the input is in an unsupported format, the input is over the size cap, or the input is structurally malformed (a truncated download, a partial export, or a stream the engine does not recognise). The first two are easy to confirm — check that your file is one of MP3, WAV, M4A, AAC, OGG, Opus, FLAC, AIFF, and WMA and that it is below 200 MB. For the third, opening the file in its native viewer first is the fastest way to confirm the source is intact.
Once the page is loaded, Audio Speed Changer can complete jobs without an active internet connection — the engine is bundled with the page, so there is no per-job network call. The initial page load does require a connection (to fetch the static assets), but after that you can disconnect entirely and the tool will still work. This is a side-effect of the local-first architecture, not a deliberate "offline mode" feature.
No installation is needed. Audio Speed Changer runs as a normal web page, with no browser extension, no native helper, and no separate desktop client to download. That is partly a privacy choice — extensions can request broad permissions, while a regular page is sandboxed by default — and partly a convenience one: you can use Audio Speed Changer on any computer you have temporary access to without leaving anything installed on it.
Your file is processed inside your browser by standard browser APIs. The engine reads the file's bytes from your tab's memory, computes the result, and writes the result back into the tab. You can confirm what the page does by opening developer tools and watching the Network tab during a run — the requests you see are for the tool's static assets only.
Audio Recorder
Record from your microphone directly in the browser. Pick quality (high, medium, low), toggle echo cancellation, noise suppression and auto-gain, then save to WebM/Opus or M4A/AAC. Audio is captured locally — nothing is uploaded.
Text to Speech
Type or paste text, pick a system voice, and listen instantly. Adjust speaking rate (0.5×–2×), pitch, and volume in real time. Uses your browser's built-in Web Speech API — no cloud TTS, no API keys, no costs.
Tone Generator
Generate a pure tone at any frequency from 20 Hz to 20 kHz. Pick a sine, square, triangle, or sawtooth waveform, choose duration, amplitude, and mono/stereo. Exports a 16-bit PCM WAV file at 44.1 kHz with built-in click-preventing fades.
Silence Generator
Generate a perfectly silent WAV file of any length from 1 second up to 1 hour. Pick mono or stereo, get a 16-bit PCM WAV at 44.1 kHz. Useful as padding between clips, intro silence, leader audio for video timing, or test material.
White Noise Generator
Generate white, pink, or brown noise as a 16-bit PCM WAV file. Pick noise type, duration up to 1 hour, amplitude, and mono/stereo. Useful for sleep, focus, masking distractions, audio testing, and as a backing layer for ambient music.
Metronome
A precise browser-based metronome powered by the Web Audio API. Set BPM from 30 to 300, choose a time signature, accent the first beat, and use tap-tempo to sync. Click timing is sample-accurate using lookahead scheduling — much steadier than typical JavaScript setInterval beats.
Audio Trimmer
Trim any audio file to a precise start and end time. Outputs a lossless stream-copy by default (no quality loss, very fast) or re-encodes to MP3, WAV, OGG, or M4A. Files are processed entirely in your browser with FFmpeg WebAssembly.
Audio Splitter
Split a long audio file into N equal-length parts and download them as a ZIP. Each part is named sequentially. Great for chapterizing audiobooks, podcasts, or long DJ mixes. Runs entirely in your browser with FFmpeg WebAssembly.