Is this OPUS to AAC 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 OPUS 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 there a quality difference between Opus and AAC at similar bitrates?

At low bitrates (below 96 kbps), Opus is superior. Above 128 kbps, the difference is negligible in listening tests. For the output AAC, use at least 192 kbps to minimise generation loss.

What streaming platforms require AAC instead of Opus?

Apple Podcasts, Spotify (for uploads), YouTube, and most broadcast delivery platforms require MP3 or AAC/M4A. Opus is used internally by some platforms for delivery but is rarely accepted as an upload format.

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.

Opus to AAC Converter — Free, Online, No Upload

How to convert OPUS to AAC online

1
Drop your OPUS file
Drag and drop your Opus Interactive Audio Codec 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 Opus Interactive Audio Codec → Advanced Audio Coding entirely in your browser tab. Most files finish in 1–3 seconds.
3
Download your AAC
Your Advanced Audio Coding file is ready. Click Download, or grab a ZIP if you converted a batch. Close the tab and everything disappears — no copies kept anywhere.

OPUS vs AAC: format overview

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)
✗ Not supported on iOS/macOS natively

AAC

Advanced Audio Coding

Dolby, Fraunhofer, Sony, Nokia · 1997

Compression: lossy
Transparency: No

✓ Successor to MP3 — better quality at same bitrate
✓ Native support across Apple, Android, YouTube

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

AAC magic bytes: FF F1 (ADTS) / 00 00 00 xx 66 74 79 70

Why convert OPUS to AAC?

Opus has excellent browser and streaming platform support, but commercial distribution pipelines — broadcast delivery, podcast hosting platforms, Apple devices, and streaming upload portals — are built around AAC and MP3 as the accepted input formats. Apple Podcasts Connect accepts AAC/M4A. Spotify's upload portal takes MP3 or AAC. YouTube processes MP3, AAC, WAV, or FLAC. If you're taking Opus audio from a WebRTC recording, a Discord export, or a streaming pipeline and need to submit it somewhere for commercial distribution, AAC is almost always the correct output format.

AAC is also what Apple devices require for native playback. iPhone, iPad, Apple TV, HomePod, and CarPlay are all built around AAC as the primary compressed audio codec. Smart TVs running Android TV, Tizen, or webOS support AAC universally. Broadcast standards for digital radio (DAB+) and streaming (HLS) use AAC as the codec. Converting Opus to AAC opens up essentially every distribution channel that Opus is closed out of.

Both Opus and AAC are lossy codecs, so transcoding between them causes a small quality reduction. Use an AAC output bitrate of 192 kbps or higher for music to minimise this. For voice-only content, 128 kbps AAC sounds excellent. The file will be slightly larger than the Opus source at equivalent perceived quality because AAC is less efficient than Opus, particularly at lower bitrates.

Quality & file size: OPUS to AAC

Typical file sizes: OPUS 1–3 MB → AAC 2–5 MB.

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

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

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

Frequently asked questions

Privacy: how FormatDrop handles your files

Your OPUSfiles 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.