MyMediaTools

Convert M4A to WMA — Free Online Tool

Convert M4A files (AAC-encoded audio from iTunes, podcasts, or Apple devices) to WMA format using Microsoft's wmav2 codec — entirely in your browser with no uploads required. This is useful when you need Windows Media Player compatibility or are distributing audio through legacy Microsoft ecosystem tools that don't support MPEG-4 containers.

FFmpeg Command

Copy this command to run the same conversion locally with FFmpeg on your desktop. Download FFmpeg

Free — no uploads, no signups. Your files never leave your browser.

Estimated output:

Conversion Complete!

Download

How It Works

M4A files typically contain AAC-encoded audio inside an MPEG-4 container. Since WMA uses Microsoft's proprietary wmav2 codec — incompatible with AAC — the audio must be fully decoded and re-encoded during this conversion. There is no 'stream copy' shortcut here: the AAC audio is decompressed to raw PCM, then compressed again using the wmav2 codec at the target bitrate (128k by default). This is a lossy-to-lossy transcode, meaning two rounds of lossy compression are applied. The resulting .wma file is wrapped in an ASF (Advanced Systems Format) container, which is the native wrapper for WMA audio. Chapter markers and iTunes-specific metadata stored in the M4A may not be preserved, as the WMA/ASF container has different metadata conventions.

What Each Flag Does

Flag What it does
ffmpeg Invokes the FFmpeg program, the open-source multimedia processing engine running under the hood. In this browser tool, it runs as a WebAssembly binary (FFmpeg.wasm) directly in your browser without any server involvement.
-i input.m4a Specifies the input file — your source M4A file containing AAC-encoded audio in an MPEG-4 container. FFmpeg reads and demuxes this file to extract the raw AAC audio stream for decoding.
-c:a wmav2 Sets the audio encoder to wmav2, Microsoft's second-generation Windows Media Audio codec. This is required because the AAC audio from the M4A cannot be placed into a WMA container directly — it must be re-encoded using a WMA-native codec.
-b:a 128k Targets a constant audio bitrate of 128 kilobits per second for the wmav2-encoded output. This is a common default that balances file size and audio quality; for a lossy-to-lossy transcode from AAC, going significantly lower than the original source bitrate will compound quality loss.
output.wma Defines the output filename with the .wma extension, which tells FFmpeg to wrap the wmav2-encoded audio stream in an ASF (Advanced Systems Format) container — the native Microsoft container format for WMA audio files.

Common Use Cases

  • Making iTunes-purchased or Apple Podcasts audio compatible with Windows Media Player on older Windows systems that don't support MPEG-4 playback natively
  • Distributing audio content through enterprise intranet portals or legacy Microsoft SharePoint installations that are configured to serve and stream WMA files
  • Preparing audio files for older portable media players — such as early-generation Zune devices or Windows Mobile phones — that support WMA but not M4A/AAC
  • Converting podcast episodes downloaded in M4A format so they can be managed and played in Windows Media Center or older Windows-based media library software
  • Archiving audio in WMA format for use in legacy video editing projects in older versions of Windows Movie Maker, which accepted WMA but not M4A input
  • Satisfying DRM-ready submission requirements for certain Microsoft-ecosystem audio distribution pipelines that require WMA as the source format

Frequently Asked Questions

Yes, there is a real risk of audible quality loss because this conversion involves two generations of lossy compression. The original M4A contains AAC audio, which has already discarded audio data to achieve compression. Re-encoding that signal using wmav2 at the same or lower bitrate applies a second round of lossy compression. At 128k, the result is generally acceptable for speech and casual listening, but critical listeners may detect artifacts, particularly in complex musical passages. If audio fidelity matters, use the highest bitrate WMA option (320k) to minimize further degradation.
No. Chapter markers are a supported feature of the MPEG-4 container used by M4A, and they are commonly used in audiobooks and long-form podcast episodes. The WMA format uses the ASF container, which does not have a native equivalent for chapter data. When you convert an M4A with chapters to WMA, the chapter information will be lost entirely. If chapters are important for your use case, M4A is the better long-term format to retain.
Basic metadata tags such as title, artist, album, and year may be carried over during the conversion, as FFmpeg attempts to map common tag fields from the iTunes/MP4 metadata format to WMA's ASF metadata format. However, embedded album artwork and iTunes-specific tags (like podcast episode URLs or gapless playback markers) are unlikely to transfer correctly or may be dropped entirely. You should verify and re-tag the output WMA file using a tag editor like Mp3tag if metadata accuracy is important.
Replace '128k' in the '-b:a 128k' portion of the command with your desired bitrate. For example, use '-b:a 192k' or '-b:a 320k' for higher quality output, or '-b:a 96k' for a smaller file size. Keep in mind that because the source AAC audio has already been lossy-compressed, increasing the WMA bitrate beyond the original M4A's bitrate will not recover lost audio detail — it will simply make the file larger without improving perceptible quality. Matching or slightly exceeding the original bitrate is generally the best approach.
The single-file command shown here processes one file at a time, but on a desktop machine you can run it in a loop. On Linux or macOS, use: for f in *.m4a; do ffmpeg -i "$f" -c:a wmav2 -b:a 128k "${f%.m4a}.wma"; done. On Windows Command Prompt, use: for %f in (*.m4a) do ffmpeg -i "%f" -c:a wmav2 -b:a 128k "%~nf.wma". The browser-based tool on this page processes one file per session, making the FFmpeg command particularly valuable for bulk conversion workflows.
Yes, wmav2 is the better choice in virtually all cases. It is an improved version of the WMA codec with better audio quality at the same bitrate compared to wmav1. The wmav2 codec has been standard since Windows Media Player 7 (circa 2000), so compatibility with any WMA-capable device from the past two decades is essentially guaranteed. The only reason to use wmav1 would be if you specifically need to target extremely old or obscure hardware from the late 1990s that predates wmav2 support. You can switch codecs in the command by replacing '-c:a wmav2' with '-c:a wmav1'.

Technical Notes

This conversion crosses two entirely distinct proprietary ecosystems: Apple's MPEG-4/AAC stack and Microsoft's ASF/WMA stack. The AAC codec used in M4A and the wmav2 codec used in WMA are fundamentally incompatible, so a full decode-and-re-encode pipeline is mandatory — there is no lossless remux path. FFmpeg handles this by selecting the wmav2 encoder (the higher-quality second-generation WMA codec) and wrapping the output in an ASF container with the .wma extension. The default 128k bitrate is a reasonable middle ground for speech and moderate-quality music, but given that the source material is already lossy AAC, the transcode chain is inherently generational. The WMA format is lossy-only; there is no lossless WMA output option in this tool (WMA Lossless is a separate, distinct codec not covered here). Additionally, M4A's support for gapless playback metadata (used by iTunes for seamless album listening) is an MPEG-4 container feature with no equivalent in ASF, so gapless transitions will be lost. The special '-vn' flag is applied internally to ensure any incidental video streams (rare in M4A but possible) are suppressed in the output.

Related Tools

Convert M4A to AIFC Convert M4A to OGA Convert M4A to AIFF Convert MPG to WMA Convert WMV to WMA Convert 3GPP to WMA Compress M4A Trim Video or Audio M4A