Is this MP3 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 MP3 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.

Why does Discord recommend Opus over MP3?

Opus was specifically designed for low-latency streaming and voice communication. At 64 kbps, Opus sounds better than 128 kbps MP3, cutting bandwidth in half — critical for real-time streaming applications.

Is Opus widely supported enough to use?

Opus is supported in all major browsers (Chrome, Firefox, Safari, Edge), Discord, Telegram, WhatsApp, and most modern media players. For broad legacy compatibility, MP3 is still safer; for streaming and web apps, Opus is the better choice.

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.

MP3 to Opus Converter — Free, Online, No Upload

How to convert MP3 to OPUS online

1
Drop your MP3 file
Drag and drop your MPEG-1 Audio Layer III 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-1 Audio Layer III → 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.

MP3 vs OPUS: format overview

MP3

MPEG-1 Audio Layer III

Fraunhofer Society · 1993

Compression: lossy
Transparency: No

✓ Universal compatibility — plays everywhere
✓ Good compression at 128–320 kbps
✗ Lossy — artifacts at low bitrates

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)

MP3 magic bytes: 49 44 33 (ID3) / FF FB

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

Why convert MP3 to OPUS?

MP3 is a 30-year-old codec. It was designed for an era of dial-up internet and limited storage, and it made reasonable trade-offs for that era. Opus was designed for the modern web — it was built for streaming, real-time communication, and efficient delivery over variable-bandwidth connections. The gap between them is not subtle: Opus at 64 kbps produces audio quality equivalent to MP3 at 128 kbps, cutting file size and bandwidth usage in half.

The practical reason most people convert MP3 to Opus is for streaming delivery. Discord uses Opus for all voice and audio. WebRTC applications — Zoom, Google Meet, browser-based VoIP — all use Opus under the hood. If you're delivering audio to a web app, embedding audio in a PWA, or hosting audio files that browsers will stream, Opus is the more efficient choice. Podcast hosting platforms that support Ogg Opus serve smaller files to listeners without any audible difference.

The converted file will be smaller than the source MP3 at equivalent perceived quality, but won't sound better than the MP3 — Opus can't recover what the MP3 encoder already discarded. Opus is supported in all major browsers, VLC, Discord, WhatsApp, and Telegram, but not by iTunes or Apple Music natively, so it's best suited for web and streaming contexts rather than local music libraries.

Quality & file size: MP3 to OPUS

Typical file sizes: MP3 3–5 MB → OPUS 1–3 MB.

Both MP3 and OPUS use lossy compression. We transcode at high quality settings (equivalent to OPUS's recommended web quality) to minimize generational loss.

Color depth: MP3 supports standard color, OPUS supports standard color.

Transparency: MP3 does not support transparency. OPUS does not support transparency — transparent areas become solid white.

Frequently asked questions

Privacy: how FormatDrop handles your files

Your MP3files 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.