How to split a long audio file for transcription

Method 1 — Online tools (no install)

The fastest option for a one-off split. Drag the file in, set a start/end time, download the chunk. Repeat for each segment.

• mp3cut.net — drag the file in, drag the markers to set start/end, click Cut, download. Works in browser, no upload to a server.
• Clideo Cut Audio — clean UI, supports MP3, M4A, WAV, FLAC, OGG and video files.
• Online Audio Converter — handles longer files and lets you batch-export segments.

Tip: split at a natural pause (between sentences or speakers) so the transcript reads smoothly when you stitch the parts together.

Method 2 — Audacity (free desktop app)

Best for accuracy, especially if your recording has silences or pauses you want to split on. Audacity is free and open-source for macOS, Windows and Linux.

1. Download Audacity and open your audio file.
2. Use File → Import → Audio if needed. Audacity reads MP3, M4A, WAV, FLAC, OGG and more.
3. Click on the waveform at the point where you want to split (use Ctrl/Cmd+B to place a label, or drag-select the region for one part).
4. Choose File → Export → Export Selected Audio and save the first part as MP3 or WAV.
5. Select the next region, export, repeat.

For long recordings, Audacity's Analyze → Sound Finder tool finds silent regions automatically — useful for splitting podcasts or interviews on natural pauses.

Method 3 — Command line (ffmpeg)

One command splits the whole file into equal-length parts. No re-encoding, so it's instant even on a 2-hour recording. Best if you already have ffmpeg installed.

Split into 25-minute parts

ffmpeg -i input.mp3 -f segment -segment_time 1500 -c copy part_%03d.mp3

1500 is the segment length in seconds (25 min). Output files will be part_001.mp3, part_002.mp3, etc. The -c copy flag avoids re-encoding so the split is lossless and fast.

Extract a specific time range

ffmpeg -i input.mp4 -ss 00:00:00 -t 00:25:00 -c copy part1.mp4
ffmpeg -i input.mp4 -ss 00:25:00 -t 00:25:00 -c copy part2.mp4

-ss is the start time, -t is the duration. Works for video files too — the audio track is split exactly the same way.

Don't have ffmpeg yet? Install via ffmpeg.org/download or with Homebrew on macOS: brew install ffmpeg.

Putting the transcripts back together

Transcribe each part on Mictoo, then paste the results into one document in order. A few quick tips for a clean final transcript:

• Split at a pause when possible — words don't get cut in half.
• If you split mid-sentence, the first word of the next part may end up capitalized in the transcript. Easy to fix in any text editor.
• For SRT or VTT subtitles: add the previous part's total duration to every timestamp in the next part's file. A find-and-replace or a small script handles it in seconds.
• Mictoo's AI summary works best on a single transcript — combine the parts first, then re-run the summary on the joined text.