Why does the quality control change when I pick a different format?

Because the formats do not share a quality scale. MP3 and AAC are measured in kilobits per second, WAV and AIFF in bit depth, FLAC in a compression level from 0 to 12 and OGG on a Vorbis quality scale of 2 to 10. The panel shows the control that belongs to the format you selected rather than a generic slider.

Why is my file uploaded somewhere?

It is not. Two engines are used depending on the format: in page encoders for MP3, WAV and AIFF, and a bundled encoder core for everything else. The core is a static download of about thirty one megabytes that runs inside the tab, so your audio stays in the browser's memory throughout and never leaves the device.

Why are some sample rates greyed out?

Because they are above the rate of the file you loaded, and resampling upward adds no quality. It would only produce a larger file containing the same information padded out with interpolated samples. The option is disabled rather than hidden so it is clear the tool considered it.

What does the metadata setting actually do?

Preserve passes tags and cover art through where the target container supports them, and strip writes a file with no metadata at all. Preserve is the reason a conversion sometimes takes longer, since it forces the bundled encoder into the path. Fields and art may still not survive between very different formats, which the panel says outright.

Can I convert a whole folder at once?

You can drop many files and they will all be processed in one run with individual progress and downloads, and a download all control appears once several have finished. They are handled one at a time rather than in parallel, so a large batch takes roughly as long as the sum of its parts.

Audio Format Converter

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Audio Format Converter is the universal member of the converter family: pick any of nine output formats, set the quality controls that format actually exposes, and convert a batch at once. It runs the native encoders in your browser where it can, and falls back to a bundled encoder core where it must.

What is Audio Format Converter?

Drop one file or twenty, choose the target format from the grid and adjust the settings panel, which changes shape depending on what you picked. Press the convert button and each file in the queue is processed in turn, with its own progress and its own download.

What the panel exposes:

A format grid offering MP3, WAV, M4A, FLAC, OGG, AAC, AIFF, WMA and OPUS.
A quality control that follows the format: an MP3 bitrate ladder of 64, 128, 192 and 320, an AAC ladder of 96, 128, 192 and 256, a WMA ladder of 64, 128 and 192, and an OPUS ladder of 64, 96, 128 and 192.
A bit depth choice of 16 or 24 for the uncompressed formats WAV and AIFF.
A FLAC compression level from 0 to 12, defaulting to 5.
An OGG quality scale of 2, 5, 7 and 10, with a fixed bitrate alternative of 96, 128, 192 and 256.
A channel mode of original, mono or stereo, and a sample rate choice of original or 16, 24, 32, 44.1 or 48 kHz.
A metadata setting of preserve or strip, with a note that fields and cover art may not survive between very different formats.
A queue with per-file status, progress and a download each, plus a download all control once several have finished.

Two engines sit behind this interface, and the tool chooses between them. MP3, WAV and AIFF have encoders that run in the page itself, so those conversions never download the encoder core. Anything else, and any conversion with metadata set to preserve, needs the bundled core, which is roughly thirty one megabytes fetched once and then reused. The tool probes which encoders the loaded core actually provides and disables formats whose requirements are not met rather than failing part way through a batch. Sample rates above the source rate are disabled for a simple reason: resampling upwards adds no information, so the option would only create bigger files with no benefit.

What the universal tool does not promise:

The first non native conversion has to fetch and initialise the encoder core, which takes time on a slow connection.
Preserve carries tags only where the target container supports them, so album art in particular may not transfer between very different formats.
FLAC and ALAC are lossless, but converting from a lossy source cannot recover what was already discarded.
Sample rate options stop at 48 kHz, so very high rate sources are not offered a matching output.
The queue processes files one at a time, so a batch conversion is a long sequential wait rather than a parallel job.
Nothing here edits the audio: no trimming, levelling or cleanup is applied along the way.

Use it when a set of files has to end up in one format, and check the settings panel before starting rather than after, because the quality ladder changes with the format you choose. If the job is simply to make files smaller, the bitrate converter beside it opens on the setting that matters instead of on the format grid.

How to use Audio Format Converter

Drop one or more audio files onto the panel, or click to browse for them.
Choose the output format from the grid and set the quality control that format exposes.
Adjust sample rate, channel mode and metadata, remembering that rates above the source are disabled.
Press the convert button and watch each file's progress, then download individually or all at once.

When to use Audio Format Converter vs related tools

Audio Format Converter is the general purpose conversion tool, so it is the right choice whenever the output format is the open question. Bitrate/Quality Converter opens directly on the bitrate choice for the common job of making a file smaller, and the single format converters such as MP3 Converter and FLAC Converter preset one target with nothing else to configure. When the source is an unusual container that needs decoding before anything else, WMA/M4B/CAF Decoder handles that first step.

Privacy & Security

This tool runs entirely in your browser — no data ever leaves your device. There is no server round-trip, no upload, no logging, and no account required. Your input is processed locally using client-side JavaScript and is never stored, transmitted, or accessible to anyone else. When you close the tab, everything disappears.