The Audio Converter switches an audio file between MP3, WAV, M4A, AAC, OGG and FLAC entirely inside the browser tab, using a WebAssembly encoding engine rather than a server. Nothing leaves the device: the file is decoded, re-encoded and handed back to you locally, which makes the tool fast, free and safe to use on recordings that shouldn't be uploaded anywhere. This guide covers which format to pick, how the conversion works step by step, and where bitrate actually matters.
Which formats it converts, and when to use each
Six formats cover almost every situation a recording, podcast episode or voice memo will run into. The table below is the fast version; the sections after it explain the reasoning.
| Format | Lossy / lossless | Typical use | Compatibility |
|---|---|---|---|
| MP3 | Lossy | Sharing, email, messaging, podcasts | Universal — every device and platform |
| WAV | Lossless (uncompressed) | Editing, mixing, video post-production | Universal, but large file size |
| M4A / AAC | Lossy | Apple devices, streaming, voice memos | Native on iPhone, iPad, Mac; supported elsewhere |
| OGG (Vorbis) | Lossy | Web embedding, open-source projects | Chrome, Firefox, Edge; not native on Safari or older Windows apps |
| FLAC | Lossless (compressed) | Archiving, masters, audiophile listening | Wide desktop support; patchy on iOS and older hardware |
MP3 remains the default choice for anything that needs to travel: it plays on essentially every phone, laptop, car stereo and web browser built in the last two decades, and the files stay small enough to attach to an email or send over a messaging app without hitting size limits. WAV sits at the opposite end — it stores the audio without any compression at all, which is why editors and video professionals prefer it, but a few minutes of stereo audio can run into tens of megabytes. M4A (the AAC codec in an MP4 container) is the format Apple's own recording and voice memo apps produce, and it generally sounds better than MP3 at the same file size, which makes it a good middle ground when Apple-device compatibility matters. OGG is mostly a web-native codec: it plays cleanly in Chrome, Firefox and Edge and is favoured by open-source and self-hosted audio projects, but it is not natively supported in Safari or by many legacy Windows media players, so it's a poor choice for a file you're emailing to someone you don't know. FLAC compresses the file losslessly — smaller than WAV, identical in quality — and is the right target for anything you intend to keep long-term or re-edit later without ever losing fidelity.
How to convert a file step by step
The workflow is short by design. Open the Audio Converter, drop or select the source file — it can be an MP3 exported from a phone, a WAV pulled off a portable recorder, or a clip you just made with the Audio Recorder. The tool reads the file locally and shows its current format and duration. Choose the target format from the list (MP3, WAV, M4A/AAC, OGG or FLAC), and where relevant, pick a bitrate or quality setting; lossless targets like WAV and FLAC skip this step since there's no quality trade-off to make. Click convert, and the WebAssembly engine re-encodes the audio in memory — for a typical few-minute voice recording this takes a couple of seconds, longer for lengthy multi-track files. When it finishes, the converted file downloads directly to the device; nothing is stored on a remote server, and closing the tab clears the working data.
If the source audio itself is thin, clipped or noisy, converting it to a different container won't fix that — the codec only changes how the existing waveform is stored, not its quality. It's worth confirming the input microphone was working correctly before recording in the first place; running a quick check at microphone-test.org takes a few seconds and rules out a bad input device before you spend time converting and re-converting a flawed recording.
Lossy vs lossless explained
The distinction between lossy and lossless is about what happens to the original waveform during encoding, not about which files are bigger or smaller as a side effect. A lossless format — WAV or FLAC — stores every sample of the original recording, or in FLAC's case, stores it more efficiently but still perfectly reversible. Decode a FLAC file and you get back the exact same audio data that went in, bit for bit. A lossy format — MP3, AAC/M4A, OGG — actively discards information the encoder judges to be inaudible or low-priority, using psychoacoustic models built around how human hearing works, in order to shrink the file dramatically. That discarding is permanent: once audio has been encoded to MP3, the removed detail cannot be restored, even if you later convert the MP3 to WAV or FLAC. The file will look lossless afterward — it will be large and uncompressed — but the underlying quality ceiling was already set at the moment of lossy encoding.
This matters most when a file is going to be converted more than once. Converting lossless to lossy loses quality exactly once, which is expected and usually inaudible at reasonable bitrates. Converting lossy to lossy again — MP3 to AAC, for instance — compounds two separate rounds of data loss and can introduce audible artifacts, especially in the higher frequencies. The safe rule: keep a lossless master (WAV or FLAC) of anything you might need to re-encode later, and generate lossy copies (MP3, AAC, OGG) from that master on demand, rather than lossy-to-lossy.
Bitrate and quality choices
Bitrate controls how much data per second a lossy encoder is allowed to spend on the audio, and it is the single biggest factor in perceived quality for MP3, AAC and OGG output. Voice recordings — interviews, dictation, podcasts, voice memos — hold up well at 96–128 kbps, since speech occupies a narrower frequency range than music and tolerates more aggressive compression before artifacts become audible. Music and mixed content generally needs 192–256 kbps to sound transparent to most listeners, and 320 kbps is effectively the practical ceiling for MP3, beyond which further increases yield no audible improvement. AAC and OGG are somewhat more efficient encoders than MP3, meaning a 128 kbps AAC file typically sounds closer to a 160–192 kbps MP3 — worth factoring in if file size is tight but quality still matters, such as sending a voiceover track to a client.
There's no bitrate decision to make for WAV or FLAC, since lossless formats reproduce the source exactly regardless of settings; FLAC's only real choice is compression level, which trades encoding speed for file size without touching audio quality at all. If a converted file still comes out larger than expected, the Audio Compressor is built specifically for that job — it re-encodes at a lower bitrate or a more compact format to hit a target file size, which is a distinct task from format conversion even though both run through similar codecs under the hood.
The on-device privacy model: no upload, ever
Every conversion happens locally in the browser using WebAssembly, a technology that lets compiled audio codecs run at near-native speed directly on the page. The practical consequence is that the source file is never transmitted to a server: there's no upload progress bar because there's nothing to upload. This matters for anything sensitive — a confidential business call, a legal recording, medical dictation, or a voice memo containing personal information — where sending the file to a third-party server, even briefly, is a risk some users are unwilling to take. It also removes the usual annoyances of server-based converters: no file-size caps tied to a subscription tier, no queue while a shared server processes someone else's job, and no dependency on an internet connection once the page has loaded. Closing the browser tab discards the working data; there's no account, no history stored server-side, and no copy left behind to manage or delete later.
Practical scenarios
Most conversion decisions map cleanly onto what happens to the file next, rather than any abstract notion of "best" format.
- Sharing a clip by email or messaging app: convert to MP3. It's small, universally playable, and won't get rejected by attachment size limits the way a WAV file often will.
- Editing or mixing a recording: convert to WAV before loading it into an editor. Lossless, uncompressed audio gives editing software the full waveform to work with, and repeated saves during an editing session won't degrade the file the way repeated lossy re-encodes would. The Audio Editor handles trims, cuts, splits and fades directly on the waveform without needing an upload either.
- Sending audio to an iPhone, iPad or Mac: convert to M4A. It's the native format for Apple's Voice Memos, Music and Photos apps, and it plays back without any compatibility warnings on Apple hardware.
- Archiving a master recording long-term: convert to FLAC. It preserves full quality at roughly half the size of WAV, which matters when archiving years of interviews, field recordings or session masters. Recording directly to FLAC from the start with the FLAC Recorder skips the conversion step entirely for anything captured fresh.
- Embedding audio on a website: convert to OGG, since it's a lightweight, open format that Chrome and Firefox play natively without a licensing fee attached, though it's worth pairing it with an MP3 fallback for Safari visitors.
Whichever direction the conversion runs, the outcome only ever reflects the quality of the source recording. If a voice track already sounds thin, distant or clipped before conversion, it's worth reading through which audio format to record in and checking the input device itself — a quick pass through microphone-test.org confirms the microphone is actually being picked up correctly, and the site's platform guides cover common failures on Windows 11, Mac and iPhone in detail.
Frequently Asked Questions
Does converting a lossy file to WAV or FLAC improve its quality?
No. Converting MP3 or AAC to a lossless container only changes how the file is stored; the detail discarded during the original lossy encoding is gone permanently and cannot be recovered by re-encoding to a lossless format afterward.
Is the converted file ever uploaded to a server?
No. The Audio Converter decodes and re-encodes the file locally in the browser using WebAssembly, and the file downloads directly to the device once conversion finishes.
What bitrate should I use for a voice recording?
96–128 kbps in MP3 or AAC is generally sufficient for speech, since voice occupies a narrower frequency range than music and holds up well under compression. Music and mixed content usually needs 192–256 kbps to avoid audible artifacts.
Why won't an OGG file play on an iPhone or in Safari?
Safari and iOS do not natively support the OGG container, so files intended for Apple devices should be converted to M4A/AAC or MP3 instead, which both play without issue across Apple's ecosystem.
Should I convert my recording or use the Compressor instead?
Use the converter when the goal is a different format for compatibility reasons, and the Compressor when the goal is a smaller file size within the same or a lossy target format — the two tools solve related but distinct problems.
Is there a file size limit on the converter?
Since processing happens on-device rather than on a server, there's no subscription-tied upload cap; practical limits come from the device's own memory and processing power rather than any imposed quota.