Trim audio clips in Unity without leaving the Editor

Unity imports audio files, but it cannot cut them. The answers in old forum threads are an online MP3 cutter, a round trip through Audacity, or a line of code that skips the first tenth of a second. Each works, and each takes you out of what you were doing. Audio Tools lets you trim the clip where it already is, in the Editor.

Open the clip

• Right-click an audio file in the Project window and choose Edit Audio.
• Or open Tools > Audio Tools > Audio Editor and drag a file onto it, pick an AudioClip, or use Browse File… for a file outside the project.

The header shows the file name, duration, channel count and sample rate, plus the peak level of the source and of the output you are about to save.

Select the part you need

Drag across the waveform to create a selection. Drag its handles to resize it, or drag inside it to move it. Click to move the playhead without selecting, and click outside the selection to clear it. The exact start, end and duration stay visible below the waveform while you drag.

For fine work, zoom in up to 32 times with Ctrl or Cmd and the mouse wheel; the zoom centers on the pointer. Right-drag pans without changing the selection, and the wheel on its own scrolls through the clip. The keyboard covers the rest:

• Space plays or pauses, Escape clears the selection.
• Home and End jump to the start and end, Ctrl/Cmd + A selects the whole clip.
• Left and Right move the playhead. Hold Alt (Option) to move one sample at a time, or Shift for bigger steps.

Zoomed in 32 times on one word, with a 26 ms selection. Alt with the arrow keys moves the playhead one sample per press.

Listen before you save

Turn on Selection only to hear just the selected range, and Loop to repeat it while you adjust the handles. Turn Selection only off to hear the edit in the context of the whole clip. Nothing is written while you listen: every preview is built from the original samples.

Save the result

The selected range is always what gets saved, even when Selection only is off for playback. Clear the selection to save the full clip.

• Save Copy writes a new WAV next to a clip in your project. The first copy of footstep.wav is footstep_01.wav, the next footstep_02.wav, and the line at the bottom of the editor always shows the next output path.
• For a file from outside the project, Import WAV saves the result into your project, and Save As WAV… writes it wherever you choose.
• Replace Original WAV overwrites a WAV that is already in the project. It asks for confirmation and keeps a backup, and Restore Replaced Files under Advanced puts the original back.

The Output section decides the format of the new file: Match source by default, or 16-bit PCM, 24-bit PCM or 32-bit float, plus the channels and sample rate. Copies of project assets keep the original’s import settings. Changes to the edit settings themselves, such as the selection and enabled effects, work with Unity’s Undo and Redo, and they survive script recompiles while you work.

When you do not need to edit the file

Sometimes the file can stay as it is. In a Timeline, an audio clip’s Clip In value skips the start, and trimming its end in the Timeline only affects playback there. In code, you can start playback at an offset:

// Start playback 0.25 seconds into the clip without editing the file.
AudioSource source = GetComponent<AudioSource>();
source.timeSamples = Mathf.RoundToInt(0.25f * source.clip.frequency);
source.Play();

Unity’s documentation notes that AudioSource.time can be imprecise with compressed clips, so timeSamples is the safer property. This is fine when one script owns the sound. Once the same clip plays from an animation event, a UI button, a Timeline and a sound manager, editing the file is simpler: every caller gets the trimmed version. The comparison of Unity’s built-in options goes through each approach.

Trim sounds before they enter your project

If the sound you need is inside an Asset Store package, you do not have to import the whole pack to trim one file. Asset Inventory includes Audio Tools and opens any indexed sound in the same editor before import, so only the part you keep ends up in your project. See trimming Asset Store sounds before import.