Convert AAC to MP3 privately. No upload, fast, free. Works for M4A, YouTube audio. Convert advanced audio codec to universal MP3.
-c copy when possible (instant), otherwise H.264 + AAC re-encode.Why private matters: Wedding videos, work recordings, voice memos — uploading leaks them. Here, ffmpeg.wasm runs locally. No server copy.
Yes. ffmpeg.wasm runs in your browser tab. No upload endpoint exists. Your file never leaves your computer.
Free forever, no watermark, no account. Supported by ads after you click Accept.
Best under 500MB. Hard limit 1GB. For larger, use desktop Handbrake/Shutter Encoder.
If we can fast-remux (same codec, just changing container), no loss and instant. If we must re-encode (e.g., AAC→MP3 with different codec), we use CRF 23 (Balanced) — visually lossless for most.