Is this M4A to OPUS converter really free?

Yes. Up to 5 files at a time, no signup, no catch. The free tier adds a small watermark to image output — Pro ($9.99/mo or $49/yr) removes it, raises the file size limit to 500 MB, and unlocks unlimited batch conversion.

Are my files uploaded to a server?

No — and you can verify it yourself. Open DevTools → Network tab, then convert a file. You'll see zero upload requests. Everything runs right in your browser. We never see your files.

How long does conversion take?

Usually 1–3 seconds for a typical file. The very first conversion on a fresh page load may take 5–20 seconds while the converter engine loads — after that it's instant. Your CPU does all the work locally.

What is the file size limit?

Free: up to 10 MB per file, 5 files per batch. Pro: up to 500 MB per file, unlimited batch. If you're working with large videos or RAW photos, Pro is built for that.

Can I batch convert multiple M4A files at once?

Yes — drop multiple files at once (or Ctrl/Cmd+click to select them) and they all convert in parallel. Free accounts handle up to 5 files per batch; Pro has no limit.

What bitrate will the converted audio use?

We default to 192 kbps for MP3, 128 kbps for OGG/Opus, and 320 kbps for M4A/AAC. These settings are perceptually transparent — most listeners can't tell the difference in a blind test.

Will my metadata (ID3 tags, album art) be preserved?

Yes, when both formats support it. Tags carry over on conversions like MP3→M4A or FLAC→MP3. WAV has limited tag support, so some metadata may not transfer.

Is Opus better than AAC (M4A) for streaming?

Yes, for streaming purposes. Opus was specifically engineered for low-latency, efficient streaming and is the codec used by Discord, Zoom, and WebRTC. At 64 kbps, Opus matches the quality of AAC at 96 kbps.

What players and apps support Opus?

Opus is supported by all major browsers, VLC, MPV, ffplay, Discord, WhatsApp, Telegram, and most modern mobile media players. It is not natively supported by iTunes or Apple Music.

How private is this converter?

Completely private — by design, not policy. There is no upload endpoint. Files are processed right inside your browser tab and disappear the moment you close it. We collect only anonymous page-view counts; your file content is never seen or stored.

M4A to Opus Converter — Free, Online, No Upload

How to convert M4A to OPUS online

1
Drop your M4A file
Drag and drop your MPEG-4 Audio file onto the converter, or click to browse your files. You can select up to 5 at once. Nothing leaves your device — conversion happens right here in the browser.
2
Hit Convert — it happens locally
Click Convert and watch it go. There's no upload, no server queue, no waiting. The converter runs MPEG-4 Audio → Opus Interactive Audio Codec entirely in your browser tab. Most files finish in 1–3 seconds.
3
Download your OPUS
Your Opus Interactive Audio Codec file is ready. Click Download, or grab a ZIP if you converted a batch. Close the tab and everything disappears — no copies kept anywhere.

M4A vs OPUS: format overview

M4A

MPEG-4 Audio

Apple / MPEG Group · 2001

Compression: lossy
Transparency: No

✓ Better quality than MP3 at same bitrate (AAC codec)
✓ Native Apple ecosystem support
✗ Not universally supported on all Windows/Linux players

OPUS

Opus Interactive Audio Codec

IETF / Xiph.Org · 2012

Compression: lossy
Transparency: No

✓ Best low-bitrate quality of any audio codec
✓ Royalty-free and open standard (RFC 6716)

M4A magic bytes: 00 00 00 xx 66 74 79 70 4D 34 41

OPUS magic bytes: 4F 67 67 53 (Ogg container)

Why convert M4A to OPUS?

M4A (AAC) was designed for offline storage and download-based delivery — it's efficient and sounds great, but it wasn't built for the low-latency demands of real-time streaming. Opus was. It's the codec powering voice and audio in Discord, WhatsApp, Zoom, WebRTC, and Spotify's streaming layer. At 64 kbps, Opus produces audio quality that matches AAC at 96 kbps, making it the more bandwidth-efficient choice for anything that moves audio over a network.

The typical reason to convert M4A to Opus is a streaming workflow: you have audio assets in M4A from GarageBand, iTunes, or a podcast recording tool, and you need them in Opus for a web application, a WebRTC-based platform, or a streaming server. Browsers support Opus playback natively via the HTML5 audio element, making Opus-encoded audio an efficient choice for web delivery without plugin dependencies. Game developers targeting web platforms (via WebAssembly or WebGL) also frequently use Opus for compressed in-game audio.

Because M4A uses lossy AAC compression, the Opus output won't surpass the quality of the source file. Both codecs are lossy, so transcoding between them introduces a small additional quality reduction. To minimise this, use a high Opus bitrate (128 kbps or above) for the output. iTunes and Apple Music do not support Opus natively, so this conversion is suited to web and streaming contexts rather than Apple device playback.

Quality & file size: M4A to OPUS

Typical file sizes: M4A 3–6 MB → OPUS 1–3 MB.

Both M4A and OPUS use lossy compression. We transcode at high quality settings (equivalent to OPUS's recommended web quality) to minimize generational loss.

Color depth: M4A supports standard color, OPUS supports standard color.

Transparency: M4A does not support transparency. OPUS does not support transparency — transparent areas become solid white.

Frequently asked questions

Privacy: how FormatDrop handles your files

Your M4Afiles are converted 100% inside your browser. They are never uploaded to our servers, never stored, and never seen by anyone other than you. This isn't a privacy policy claim — it's an architectural guarantee: our server has no endpoint that receives file bytes.