Audio trimmer

How does in-browser audio cutting work?

The cut runs in three stages right on your device — your file never leaves the browser. In the first stage the Web Audio API reads your file and hands it to a decoder that converts it into individual samples. For a typical MP3 at 44,100 Hz stereo that’s 88,200 floating-point values per second — the raw form in which audio can be edited.

In the second stage these samples become a compact waveform display: per pixel column, the minimum and maximum amplitude is computed (min/max peaks). This is the standard approach in professional audio editors — the waveform isn’t the audio itself, it’s an efficient visualisation. For a two-hour recording, roughly 32 KB of peaks data is enough for the entire display.

In the third stage — when you click “Export” — the selected range is decoded again (only the cut portion this time, not the whole file) and encoded into the target format. WAV gets a standard RIFF header and the raw samples, MP3 runs through a Pulse-Code Modulation-to-MPEG encoder, M4A uses the browser’s native AAC encoder.

Why dual-view: overview and detail at the same time?

The two waveforms solve a standard problem with browser audio cutters: for a one-hour recording, a single waveform is typically one pixel per second wide — far too coarse to land precisely on a 5-second snippet. The upper overview always shows the whole track (handy for finding the rough spot), the lower detail strip zooms into the current window (handy for sample-accurate cut placement).

Click in the overview to scroll the detail window to the clicked position. Scroll wheel or pinch gesture in the detail strip zooms in and out. The selection stays stable while zooming — so you can navigate roughly with the overview, then fine-tune with the detail zoom, without having to re-set the selection range.

Why does 100 % in-browser cutting matter?

Audio can be very personal: voice notes from your partner, interview recordings under NDA, voicemail from your lawyer, family conversations, medical consultations. Browser cutters that upload files give you no proof of what happens to the data after the upload. Even if the provider promises “auto-delete after 24 hours” — the data sat on a server administered by employees for those hours.

No upload happens here. There’s no server that gets to see your file. You can verify this by switching off Wi-Fi: once the page is loaded, the trimmer keeps working offline. Convenient on a train, on a plane, or during research trips with patchy connections.

Which output format is right?

Three formats are available, each with its own trade-offs:

• MP3 is the default for most use cases. One minute of stereo audio @ 192 kbps takes up roughly 1.4 MB. MP3 is understood by virtually every player and editor. Re-encoding from an MP3 source produces a tiny generational loss that’s usually inaudible during normal listening.
• WAV is the lossless format. One minute of stereo audio @ 44.1 kHz takes up roughly 10 MB — about seven times the size of MP3. Worth it if you’ll process the result further (mastering, sound design, multiple re-exports) and want to avoid quality loss.
• M4A sits between the two — compressed like MP3 but with the more modern AAC codec, which sounds slightly better at the same bitrate. First choice if the result will end up on an iPhone or iPad (Apple Voice Memos, AirDrop sharing). M4A is hidden in browsers without AAC encoder support.

How do you cut cleanly?

• Work in detail zoom: the overview is for navigation, the detail view is for precise cut placement. All the important drag operations happen in the lower view.
• Cut on silence where possible: cuts mid-word, mid-syllable or mid-musical-note are audible. Cut at pauses for natural transitions.
• Use the time inputs for precision: if you have an exact second in mind (e.g. “chorus starts at 1:23.500”), type it directly into the input field instead of hunting for it with drag.
• Preview with loop: enable the Loop button, then Spacebar. The range plays endlessly — ideal for testing a tricky cut point.
• Start with Z on long recordings: press Z once and the detail view zooms onto the current selection. Saves manual scrolling.

What can you use this for?

Make a ringtone from a song. Upload your favourite track, mark the chorus (typically 20–30 seconds), export as M4A and load it onto your iPhone. Apple accepts M4A files directly as ringtones.

Trim a voice memo. A voice note from an iPhone often has a few seconds of silence at the start (from “tap record” to “start speaking”) and end (from stop-speaking to “tap stop”). Both ranges trimmed away with the drag handles, exported as MP3.

Podcast highlight for social media. A 60-minute interview often contains 2–3 quotable moments. The overview waveform helps you find them, the detail zoom helps you cut precisely. 30–60 second quotes exported as M4A or MP3 — slot directly into TikTok, Reels or LinkedIn Audio.

Audiobook excerpt to share. Extract two minutes of “preview” from an 8-hour audiobook. The tool handles the length; for large files (>300 MB) only a performance hint appears.

Trim silence between recordings. When you’ve made several short voice recordings back-to-back and want to remove the pauses afterwards.

Which tools pair well?

From the kittokit ecosystem for the audio workflow:

• Audio transcription — turn spoken audio into text with timestamps for subtitles. Works on the same format spectrum.
• Speech enhancer — remove noise, echo and background sound from recordings. Useful before cutting if the audio track needs improvement.
• HEVC to H.264 — if you want to extract audio from a video, convert the video to a common format first and then drop the audio track in here.