To extract the sound, open the recording in the converter. This guide covers where each recorder saves the file, what to check before converting, and what the converter does with a recording that holds more than one audio track.
A screen recording is not an MP3
The capture is a video container — MP4, MOV, MKV or WebM — with a picture track and at least one audio track. Extracting audio writes a new sound file. It does not convert the recording itself into an MP3, and it does not fetch a file from a website. Open a file already on this device in the converter, then press Convert and Save file.
Find the recording on your device first
The recorder decides the container, and the container decides which export paths are open. Look at the file before opening it here.
- Mac. Apple documents that screen recordings made with the Screenshot tool “are saved as .mov files”, on the desktop by default, with names that begin with “Screen Recording” and include the date and time. MOV with AAC audio is the case where an unchanged M4A copy is usually possible. (Apple: take a screenshot or screen recording on Mac)
- Windows, Xbox Game Bar. Microsoft documents that Windows key + Alt + R starts and stops a recording, Windows key + Alt + M toggles the microphone, and the result is an MP4 file under Videos in a folder called Captures. (Microsoft: record your screen with Xbox Game Bar)
- iPhone. Apple says a screen recording is found in the Photos app, in your Library, and that the microphone is turned on by touching and holding the Record button before starting. If you pick it from Photos in the browser, iOS may prepare a converted copy first; saving the recording to Files and choosing it through Browse avoids that step. (Apple: record the screen on iPhone)
- Android. Google’s help page puts screen recordings in Photos under Collections, On this device, Movies, and the recorder asks whether to record audio before it starts. Exact menus differ between phone makers. (Google: take a screenshot or record your screen on Android)
After the file opens, the File check panel under the waveform shows what the recorder actually wrote: the container, every audio track with its name, codec, channels, sample rate and measured bitrate, which export path the current choice will take, and the expected size of each output. If the recording has no audio track, the page says so before any conversion starts, which usually means audio capture was off when recording. The screen recording test results list what that panel reported for five test captures and how long each export took.
What a two-track recording looks like: the sample
Every tool page has an Open the sample recording button under the drop zone, for when there is no recording at hand. The sample is a generated test file, not the output of a real recorder: 20 seconds of Matroska, 474,107 bytes, made with FFmpeg from a 320×180 test pattern and two audio tracks. Track 1, named System audio, is AAC stereo encoded at 96 kbps and carries a 220 Hz tone with quiet pink noise. Track 2, named Microphone, is Opus mono encoded with a 32 kbps target and carries a 440 Hz tone that sounds for 1.8 seconds out of every 3, standing in for speech with pauses. Its SHA-256 is 8880b2c704b8aa42410cbc22e135b36ebe845c1ef3fce03172b2aa54503f0c41.
Opened in desktop Chrome on 13 October 2026, File check listed both tracks by name with language, codec, channels and the 48 kHz sample rate, and measured 96 kbps for System audio and 46 kbps for Microphone. The second figure is above the 32 kbps the file was encoded with, because File check adds up the packets that are actually in the file rather than reading a setting. These are the files the converter saved:
| Track | Output | Saved size |
|---|---|---|
| 1. System audio (AAC stereo) | MP3, 192 kbps | 481,704 bytes |
| 1. System audio (AAC stereo) | M4A, unchanged copy | 250,276 bytes |
| 1. System audio (AAC stereo) | WAV, 16-bit | 3,844,076 bytes |
| 2. Microphone (Opus mono) | MP3, 192 kbps | 481,128 bytes |
| 2. Microphone (Opus mono) | M4A, new AAC encode | 485,294 bytes |
| 2. Microphone (Opus mono) | WAV, 16-bit | 1,921,340 bytes |
Three things in that table apply to real recordings too. The MP3 is the same size for both tracks, because the converter has one MP3 rate and a mono source does not lower it. The unchanged M4A copy is only offered for the AAC track; the Opus track has to be encoded again, so its M4A is about twice the size of the copy. WAV halves for the mono track, because WAV size is set by channels, sample rate and duration, not by how the source was compressed.
The input file is not copied into memory
A long screen capture is handled differently from a conventional whole-file converter. PrivateMP3 asks the local file for ranges as they are needed. It does not decode the picture frames. For the waveform, decoded audio is reduced to minimum and maximum peaks for time buckets rather than retained as full PCM. This makes the page useful for a lecture you recorded, a meeting captured with permission, a tutorial you made or another local screen recording where only the sound is needed.
The output can be the memory problem
The completed audio still has to be stored somewhere. PrivateMP3 normally streams it into the Origin Private File System, browser-managed storage on the same device, and exposes it through Save file when finished. If that interface is unavailable, the worker falls back to an in-memory output buffer. A long result is more demanding on that fallback even though the source continues to be read in ranges.
Duration still costs time and storage
The browser must decode the audio timeline, build waveform peaks and encode every kept sample. Device speed, free storage, audio codec and output format therefore matter. The picture resolution is not sent to the audio encoder, but the container still has to be read; two recordings of equal duration should not be promised equal processing times.
Keep the tab open and the device awake. The page requests a screen wake lock while converting when the browser allows it, but system power controls can still suspend a background tab.
Check the tracks before converting
A capture may store microphone and system audio as separate tracks, or mix them into one. When several audio tracks exist, a picker appears with codec and channel information. PrivateMP3 can select one track. It cannot combine tracks, separate speakers from a mix or recover audio that the recorder never captured. An interrupted recording may also be missing packets or final container metadata.
Choose the output for the job
- MP3 uses 192 kbps. It favors compatibility, not the smallest possible speech file; no lower bitrate is available here.
- M4A can copy a complete, unchanged AAC track from an MP4 or MOV. Cuts and volume changes force a new AAC encode. Opus from WebM cannot use this copy path.
- WAV writes 16-bit PCM for editing or analysis and grows directly with duration, sample rate and channel count.
Remove an empty introduction, long break or unused ending before export. The output-duration estimate updates to reflect what remains. To check whether the result will fit a size limit before converting, use the size calculator.