Search for "convert audio online" and you land on a page with a big upload button. The file goes to somebody's server, gets transcoded there, and comes back as a download link. If the file is a voice memo, a rehearsal take or a podcast master, you have just handed it to a third party to do a job your browser can do on its own.
The OnePassApps Audio Studio does the conversion in the tab, on your machine. I work on OnePassApps, so here is what it actually does - with the output I watched it produce.
The Convert tool, panel by panel
The Audio Studio has four tabs: Convert, Compress, Trim and Extract. The Convert panel runs in three steps:
- 01 Source - the audio file goes here.
- 02 Options - "Format, sample rate and channels appear here once the file has been checked against this browser."
- 03 Result - "A copy in WAV, or another format this browser can encode. Your original stays unchanged."
That middle step is the important one. The options are not a fixed list of formats the site happens to support - they are what your browser can actually encode. The tool checks the file first, then offers you the encoders that exist on your machine.
What you can drop on it
The source stage accepts: MP3, WAV, M4A, AAC, OGG, Opus, FLAC or WebM, up to 32 MiB and 45 minutes.
The panel's own hint says it plainly: "No file yet. Drop one on the stage or browse for it. Up to 32 MiB and 45 minutes."
The options, as they appear
Once a file is loaded, three controls show up:
- Output format - a dropdown with WAV audio (PCM) and WebM audio (Opus) in this browser.
- Sample rate - 48,000 Hz, 44,100 Hz, 32,000 Hz, 24,000 Hz or 16,000 Hz.
- Channels - the source's channel layout, kept by default.
Underneath them the panel notes: "Defaults keep the source's mono and sample rate when the chosen encoder supports them."
So the defaults are not arbitrary. If your file is 44.1 kHz mono, the copy comes out 44.1 kHz mono unless you change it.
What it actually produced
I ran it on a real 2-second WAV file to check the claims rather than repeat the panel copy.
The source stage read the file locally and reported: tone.wav, 0:02.0 · Mono · 44.1 kHz, with the inspection line "WAVE inspected locally. PCM-S16 audio, 0:02.0." - and the detail panel listed Container WAVE, Audio codec PCM-S16, Sample rate 44,100 Hz, Channels Mono.
With the format left at WAV audio (PCM), the result stage read:
tone-converted.wav
0:02.0 · 172 KiB
Download WAV
Then I changed the output format to WebM audio (Opus) and ran it again:
tone-converted.webm
0:02.0 · 32.9 KiB
Download WebM
The detail panel confirmed the change: Format WebM Opus, Sample rate 44,100 Hz, Channels Mono, Size 32.9 KiB. Same 2 seconds of audio, from 172 KiB to 32.9 KiB, and the result line says what that means for you: "Output created locally. Your original file remains unchanged."
Your original file is never overwritten. The tool produces a copy.
Why it stays on your machine
The page says it in two places. Above the tools: "Convert, compress, trim and extract audio locally. Your media stays in this browser tab." Under the picker: "Processing stays in this browser."
There is no upload step, no account to create and no card to add. The one practical consequence: export your result before you close the tab. The file is yours to keep, and nothing is waiting on a server for you.
The same studio does the other three jobs
While you are in there, the other three tabs work the same way:
- Compress offers "Format, bitrate, sample rate and channels appear here once the file has been checked."
- Trim keeps only the range you want: "Drag the handles on the stage or type exact start and end times once the file has been checked," and the result is "A new file with only the range you keep. Your original stays unchanged."
- Extract pulls the audio out of a video: "The primary audio track as its own file. The video stays unchanged."
All four tabs take the same source formats (up to 32 MiB and 45 minutes) and work on the same rule: the media never leaves the tab.
What it costs right now
The studios are browser-local, so they need no account and use no credits. The plan block on the page reads: "FREE PROMOTIONAL PERIOD - Standard is free right now - $0 / month", with "100,000 credits every 30 days · No end date set · No card required" and "No automatic paid subscription. Existing paid subscriptions keep their terms."
Try it
Open the Audio Studio and convert a file you would rather not upload:
One caveat worth repeating from my own test: the format list depends on what the browser can encode, so it may offer you different options than mine did. Check the dropdown rather than assuming.
And to be plain about the trade-off: Opus at 32.9 KiB is lossy. If you need a bit-exact copy, keep the source format or the source file. The value here is that the file was never on a server you do not control.
To be clear about who is writing this: I work on OnePassApps. Every limit, format and output string above was read off the live Audio Studio or produced by running the tool in my own browser, so you can check each one yourself by opening the studio.
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