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OPUS

AAC to Opus Converter — Free, Online, No Upload

Opus uses bandwidth more efficiently than AAC for streaming — switch your audio assets for faster, cheaper delivery.

Free · no signup2 free files a day100% in-browser · no upload

Tap to select AAC files

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2 free files per day (2 left today) · Up to 10 MB each · Upgrade for more

✓ Files never uploaded✓ 100% browser-based✓ No account required
Need the reverse?OPUS → AAC

How to convert AAC to OPUS online

  1. 1

    Drop your AAC file

    Drag your Advanced Audio Coding file onto the box above, or click it to pick a file.

  2. 2

    Wait a few seconds

    Conversion starts on its own and runs on your device, not on a server.

  3. 3

    Download your OPUS

    Click Download to save the Opus Interactive Audio Codec file.

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. This converter writes Opus at 192 kbps, which keeps that loss small. 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 sizes (3-minute song): AAC 2–5 MB → OPUS 1–3 MB.

OPUS output is encoded at 192 kbps.

Re-encoding one lossy format into another adds a second round of compression.

Frequently asked questions

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.

Your AAC file never leaves this tab — FormatDrop has no endpoint that receives file data. How it works