Convert Audio Files in Your Browser: WAV or OGG, and Why OGG Takes Real Time
Audio conversion in a browser is genuinely local work: the file is decoded, resampled and re-encoded inside your tab, and only the finished file is handed back to you as a download. Audio Format Converter and Video Audio Extractor split that job in two, and each has one behaviour worth knowing before you queue up a batch.
What "converting" actually does
Both tools follow the same pipeline: decode the compressed source into raw samples, then write those samples out again. The intermediate form is always uncompressed PCM. That has one consequence people are often surprised by — converting MP3 to WAV does not improve the audio. It restores no data that lossy encoding already discarded; it only stops throwing more away. The file gets bigger, the quality stays exactly where it was.
Conversely, converting WAV to a lossy format does cost you something, and each re-encode compounds it. Keep a master copy uncompressed and encode from it every time, rather than converting an MP3 into another MP3.
WAV output is always 16-bit PCM
The converter offers exactly two targets: WAV (16-bit PCM) and OGG (Opus), with WAV as the default.
The WAV writer is hand-built rather than delegated to the browser, and it always writes 16-bit integers. A 24-bit recording from a DAW comes out as 16-bit. A floating-point file comes out as 16-bit. Nothing is dithered and no bit-depth control is exposed — if you need 24-bit output, this is the wrong tool, and the same applies to 32-bit float.
What you can control is the sample rate: Source rate (the default), 44100 Hz, or 48000 Hz. Leaving it on the source rate means the tool skips resampling entirely, which is the right answer unless you have a specific target. Downsampling 96 kHz material to 44.1 kHz is a real, permanent loss; upshifting 44.1 to 48 does nothing good except make the file larger. If you must match a delivery spec, change it here rather than in a separate step afterwards.
Expect roughly 10 MB per minute for stereo at 44.1 kHz and about 5 MB per minute for mono. A three-minute stereo song lands near 31 MB, which matters if you are batch-converting a folder.
OGG encoding runs in real time
This is the behaviour that catches people out. The Opus path does not encode offline — the tool plays the decoded audio through a recording API and captures what comes out. So encoding a three-minute track takes about three minutes of wall-clock time, and the tab has to stay in the foreground and unmuted while it runs. Switch tabs, minimise the window, or let the laptop sleep, and the recording can stall or come out short.
Two further details:
- If the browser cannot record OGG with Opus, the tool falls back through
audio/oggand thenaudio/webm;codecs=opus. If none of them work, you get an explicit message telling you to use WAV instead. - Output files are named from the selected format, so a successful fallback produces a file called
song.oggwhose actual container is WebM. Most players sort this out by sniffing the contents, but if a strict tool rejects it, rename the extension to.webmand it will usually load.
Rule of thumb: use WAV when you want a predictable file you can feed to anything else, use OGG only when you specifically want Opus and can leave the tab alone while it runs.
Batch mode and the ZIP
The converter accepts multiple files at once — drag a whole folder in. Files your browser cannot decode as audio are skipped rather than reported, so if two of the twelve items you added never appear in the list, they were filtered, not lost.
Each item shows its own status while the queue runs: waiting, decoding, converting, done, or an error naming what went wrong. Individual downloads are available as each file finishes; Download All as ZIP packages the completed ones as audio-converted.zip. Single-file downloads are named after the source with the chosen extension — track.mp3 converted to WAV becomes track.wav.
For long batches the page keeps the screen awake, because a display that sleeps halfway through an OGG run would take the tab down with it.
Extracting sound from a video
If the audio is inside a video file, use Video Audio Extractor — it is a different job with different limits.
It accepts MP4, WebM, AVI, MOV and MKV up to 200 MB, and produces a single 16-bit WAV. The output is named after the video, so screen-rec.mp4 becomes screen-rec.wav. (MKV is accepted when you drag the file onto the zone, though the file picker's own filter lists only the other four.)
There are two internal routes, and which one you get quietly changes the result:
- Normal path — the whole file is decoded, so the WAV keeps the video's true channel count and sample rate. A stereo 48 kHz recording gives a stereo 48 kHz WAV.
- Fallback path — if decoding fails, the tool captures the video element's audio stream instead. That forces two channels and your playback device's sample rate, regardless of the source. The result panel says "via video stream capture method" when this happens. Treat that label as a caution: this route can produce a file that differs from the original spec — and occasionally one that is silent while still reporting success. Listen before you use it.
You cannot extract audio from a DRM-protected or unusually packed file — the browser's decoder is the limit, which is also why the fallback exists at all.
Which tool for which job
| You have | You want | Use |
|---|---|---|
| MP3, FLAC, OGG, M4A | Uncompressed master for editing | Audio Format Converter → WAV |
| WAV or AIFF | Smaller file to share | Audio Format Converter → OGG (leave the tab alone) |
| Any audio | Same format, different sample rate | Audio Format Converter, set the rate explicitly |
| MP4, MOV, screen recording | Just the soundtrack | Video Audio Extractor |
| Video with no decodable audio track | Anything | Neither tool — the decoder fails first |
If a file refuses to convert
- Silence in the file list after dropping it — the browser could not identify it as audio. Try converting the extension to match the real codec, or test the file in a player first.
- "OGG recording is not supported" — your browser will not record that container. Switch the target to WAV.
- A converted file plays at the wrong speed — the source had an unusual sample rate; convert again with the rate pinned explicitly instead of keeping the source.
- Extract fails on a large video — the 200 MB ceiling is enforced before anything is decoded. Trim or compress the video first.
Privacy
Audio is read into the tab and processed there. No upload, no account, no server-side queue, and the finished file is a local blob you download directly. These pages load analytics and advertising scripts like the rest of the site, but the audio data does not leave your machine. The one exception worth naming: batch ZIP packaging uses a script loaded from a CDN, so that specific feature needs an internet connection.
Related guides
- How to trim an audio file online — cutting a converted WAV to length, and reading a BPM result
- Capturing video frames and making a GIF — the picture half of the same video files