Is this AAC 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 AAC 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 technically better than AAC?

For streaming and real-time communication, yes — Opus has lower latency and better quality-per-bitrate than AAC below 128 kbps. At high bitrates (256 kbps+), the difference is negligible.

Which streaming platforms support Opus?

Discord, Zoom, Google Meet, Microsoft Teams (for WebRTC), Spotify (via Ogg Opus), and all web browsers support Opus. Apple platforms and iTunes still prefer AAC.

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.

AAC to Opus Converter — Free, Online, No Upload

How to convert AAC to OPUS online

1
Drop your AAC file
Drag and drop your Advanced Audio Coding 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 Advanced Audio Coding → 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.

AAC vs OPUS: format overview

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
✗ Not fully royalty-free

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)

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

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

Why convert AAC to OPUS?

AAC is efficient for stored audio, but Opus is engineered for audio in motion — real-time streaming, VoIP, and web delivery at the lowest practical bitrate. The performance gap is most visible below 128 kbps: at 64 kbps, Opus sounds markedly better than AAC at the same bitrate, with better high-frequency reproduction and fewer compression artifacts. Above 128 kbps, the difference narrows considerably.

The practical motivation for this conversion is usually a streaming or WebRTC context. Discord requires Opus for bot audio uploads. Telegram voice messages are Opus. Zoom, Google Meet, and browser-based communication tools all use Opus for audio transport. If you're building a web application that serves audio, Opus in an OGG container is natively supported by all major browsers and typically produces smaller files than equivalent-quality AAC. Spotify uses Ogg Opus internally for some delivery tiers. Web developers serving podcast audio or music on their own infrastructure find Opus particularly effective for mobile users on variable connections.

Both AAC and Opus are lossy, so transcoding between them causes a small additional quality reduction. Use a high Opus output bitrate (96–128 kbps) to minimise this. Opus is not supported natively by iTunes or Apple Music, and iOS's native audio player doesn't handle Opus files — so this conversion is best suited to web and streaming deployment rather than Apple ecosystem use.

Quality & file size: AAC to OPUS

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

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

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

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

Frequently asked questions

Privacy: how FormatDrop handles your files

Your AACfiles 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.