Video trimmer

How does in-browser video cutting work?

The cut runs in four stages right on your device — your file never leaves the browser. In the first stage the Web Audio API reads the audio track of your video and feeds it to a decoder. In parallel, the hardware-accelerated browser pipeline pulls still frames at regular intervals — those become the thumbnail strip up top.

In the second stage these audio samples become a waveform display: per pixel column, the minimum and maximum amplitude is computed (min/max peaks). This is the standard approach in professional video editors — the waveform isn’t the audio itself, it’s an efficient visualisation. The audio track is almost more important than the picture for video cutting: sentences, pauses, music cues and speaker transitions are usually clearer in the audio than in the image.

In the third stage — when you click “Play” — the video plays in the preview above with image and sound in sync. You see and hear only your selected range.

In the fourth stage — when you click “Export” — the selected range is re-encoded: H.264 for video, AAC for audio, in an MP4 container. The original frame rate is preserved.

Why the thumbnail strip with still frames on top?

For long videos — webinars, talks, family gathering recordings — the audio waveform alone isn’t expressive enough to find the right spot. You can tell that someone’s speaking, but not what’s happening on screen.

The thumbnail strip solves exactly this: it pulls still frames at regular intervals across the whole video and shows them as a mini strip on top. You see at a glance: here’s slide 12, here comes the Q&A, here the cake gets cut. It’s not a real watching preview — it’s a map. Click anywhere in the strip to scroll the detail row below to that point.

How do you cut cleanly?

• Work precisely in the detail row: the thumbnail strip on top is for navigation, the detail row below is for cutting precisely with the audio waveform.
• Cut on silence where possible: cuts mid-word are audible. Where the waveform is flat (speech pause), there’s a natural transition.
• 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.
• 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 and the detail view zooms onto the current selection. Saves manual scrolling.

What can ‘Auto-trim silence’ do?

The algorithm scans the entire audio track of your video and finds quiet stretches longer than 500 milliseconds (typical for speech pauses, “uhms” at the start and end, long breaths). What’s left are the speech segments worth keeping.

These are visualised in the detail waveform as orange tints — each segment with its own drag handles and an × button. You can fine-tune the suggestions (drag an edge, remove a falsely-detected segment) before exporting. On export, all kept segments get joined into one continuous file with short crossfades so nothing clicks.

Typical use case: a 90-minute recorded talk gets condensed in 5 seconds to 65 minutes of pure speech material. Saves viewers time and the editor manual cutting work.

What do the quality presets mean?

Three presets control the video bitrate on re-encode:

• Original keeps the estimated source bitrate. Best image quality, largest file. Default recommendation if the result will be edited further or archive quality matters.
• Balanced drops to 60 % of source bitrate. Indistinguishable to a casual viewer. File is markedly smaller — good compromise for web publishing, cloud sharing or social media.
• Small drops to 35 %. Visible compression artefacts on close inspection, but acceptable for email attachments, WhatsApp sharing or Slack uploads. Audio is unaffected — AAC at full original quality.

Which tools pair well?

From the kittokit ecosystem for the video workflow:

• HEVC to H.264 — if your video is in HEVC codec (iPhone recordings, Sony cameras), convert it first before cutting. Some browsers still struggle with HEVC decoding.
• Audio cutter — if you only want to keep the audio of a video, extract the right range here first with the video cutter, then use the audio cutter for pure MP3/WAV/M4A output.
• Video background remover — make the background transparent for Reels, Shorts or chroma-key composites.