Add as many files as you like. They are converted one after another on this device, and nothing is uploaded.
Which format to choose
MP3 plays on practically every phone, car stereo and computer, so it is the safe choice for sharing. M4A uses AAC, which sounds a little better than MP3 at the same size and suits Apple devices. OGG uses the Opus codec, which is very efficient and popular for the web and games. WAV is uncompressed, so it is large but ideal for editing. FLAC appears when your browser can encode it; it is lossless like WAV but about half the size.
Choosing the quality
The kbps number is how much data each second of sound may use. Higher numbers sound closer to the original and make bigger files. Converting from one lossy format to another cannot add back detail that was already removed, so there is little point in choosing a higher quality than the source. If your browser cannot encode at the rate you picked, the closest lower rate is used and shown next to the file.
Sound from videos
Add an MP4, MOV, MKV or WebM video and only its soundtrack is kept, which is handy for saving a talk, a lesson or a song from a clip you recorded. The picture is ignored, so this is quick even for long videos.
Private by design
Your browser reads each file, converts it with its own built-in audio engine and offers the result straight from memory. There is no server that receives your recordings, so voice memos, interviews and unreleased music stay on this device. Very large batches use more memory, so a phone handles fewer long files at once than a computer.