Convert WebM to ALAC — Free Online Tool
Convert WebM audio to ALAC (Apple Lossless Audio Codec), extracting the Opus or Vorbis audio track from your WebM file and re-encoding it into a lossless .m4a file compatible with iTunes, Apple Music, and the broader Apple ecosystem. Because WebM uses lossy codecs (Opus or Vorbis) and ALAC is lossless, the output preserves every detail of the lossy source without any additional quality degradation.
to
FFmpeg Command
Copy this command to run the same conversion locally with FFmpeg on your desktop. Download FFmpeg
Drop your WebM file here
or click to browse
Free — no uploads, no signups. Your files never leave your browser.
Settings
Note: Browser-based encoding uses approximate quality targets. For precise CRF compression, copy the FFmpeg command above and run it on your desktop.
Estimated output:
Conversion Complete!
DownloadHow It Works
WebM files carry audio encoded with either Opus or Vorbis — both lossy codecs optimized for web streaming. During this conversion, FFmpeg discards the VP9 video stream entirely and re-encodes only the audio track using Apple's ALAC codec, wrapping it in an MPEG-4 (.m4a) container. Because ALAC is lossless, it captures a mathematically perfect representation of the decoded Opus or Vorbis audio — meaning no further quality is lost beyond what was already sacrificed when the original WebM was created. The output file will be noticeably larger than the source WebM audio, since lossless compression is less aggressive than Opus or Vorbis, but it is fully compatible with Apple devices, iTunes, Logic Pro, and any software that reads standard ALAC/M4A files.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg binary — the open-source multimedia processing engine that powers this conversion both in the browser (via FFmpeg.wasm) and on the desktop command line. |
-i input.webm
|
Specifies the input file: a WebM container, which typically holds a VP9 video stream and an Opus or Vorbis audio stream. FFmpeg reads and demuxes both streams, making them available for selective processing. |
-c:a alac
|
Sets the audio codec to ALAC (Apple Lossless Audio Codec). FFmpeg decodes the source Opus or Vorbis audio to raw PCM and then re-encodes it using ALAC, producing a lossless audio stream suitable for the M4A container and the Apple ecosystem. This flag appears twice in the resolved command, which is redundant but harmless — the second instance simply reaffirms the same codec selection. |
-c:a alac
|
A duplicate of the preceding codec flag as resolved by this tool. In practice, only one instance is needed; both instruct FFmpeg to use the ALAC encoder for the audio output stream, and the second occurrence does not change the behavior. |
output.m4a
|
Defines the output filename and, critically, its .m4a extension. FFmpeg uses the extension to select the MPEG-4 audio container, which is the standard wrapper for ALAC files and is required for compatibility with iTunes, Apple Music, iPhone, and other Apple software. |
Common Use Cases
- Archiving the audio from a WebM lecture, podcast, or interview download into a lossless format for long-term storage in an Apple ecosystem library
- Importing a WebM music file downloaded from a web source into iTunes or Apple Music, which does not natively support the WebM container or Opus/Vorbis codecs
- Preparing audio assets from WebM screen recordings or game captures for editing in Logic Pro or GarageBand, which work natively with ALAC/M4A
- Stripping the VP9 video from a WebM file to produce a standalone, high-fidelity audio file for use in Final Cut Pro X projects
- Converting a web-sourced WebM audio track to ALAC so it can be synced to an iPhone or iPad via Finder or iTunes without format compatibility errors
- Creating an ALAC master copy of a WebM audio file before further processing or distribution, ensuring no generation loss from repeated re-encoding
Frequently Asked Questions
No — and this is an important distinction. The WebM file's audio is already encoded with a lossy codec (Opus or Vorbis), meaning some audio information was permanently discarded when the WebM was created. ALAC is a lossless format, so it will perfectly preserve the decoded output of that lossy source, but it cannot recover data that was already lost. The result is a lossless copy of a lossy original — no worse than the source, but not better.
Opus and Vorbis are highly efficient lossy codecs that achieve small file sizes by permanently removing audio data the human ear is less sensitive to. ALAC, by contrast, is lossless and uses a form of lossless compression similar to ZIP — it keeps every sample intact, which results in significantly larger files. For a typical WebM file with 128k Opus audio, you can expect the ALAC output to be several times larger, reflecting the full uncompressed-equivalent audio data.
Both WebM and ALAC/M4A containers support chapters, so chapter metadata may survive the conversion if the source WebM contains chapter information. However, FFmpeg's handling of WebM chapter-to-M4A chapter mapping can be inconsistent in practice. If chapter preservation is critical, verify the output with a tool like MediaInfo or mp4chaps after conversion.
The VP9 video stream is dropped entirely. ALAC is an audio-only codec and the M4A container is intended for audio, so there is no mechanism to carry video. The output .m4a file contains only the re-encoded ALAC audio track. If you need to keep the video, you should convert to a different output format that supports both video and audio, such as MP4 or MKV.
Yes. On the command line, you can use a shell loop to process multiple files. On Linux or macOS, run: for f in *.webm; do ffmpeg -i "$f" -c:a alac "${f%.webm}.m4a"; done. On Windows Command Prompt, use: for %f in (*.webm) do ffmpeg -i "%f" -c:a alac "%~nf.m4a". The browser-based tool processes one file at a time, but the displayed FFmpeg command is designed to be run locally for bulk workflows or files over 1GB.
Yes — despite being developed by Apple, ALAC was open-sourced in 2011 and is now supported by a wide range of software beyond the Apple ecosystem, including VLC, foobar2000, Plex, Kodi, and most modern DAWs. Android devices and Windows 10/11 also support ALAC playback natively or through common media players, though it remains most seamlessly integrated with Apple platforms like iTunes, Apple Music, iPhone, and Mac.
Technical Notes
WebM audio tracks in the wild are almost exclusively encoded with Opus (the modern default) or Vorbis (older files). Both are lossy codecs, so the ALAC output — while lossless in its own right — is bounded by the quality ceiling of the source. The conversion involves a full decode-then-encode cycle: FFmpeg decodes the Opus or Vorbis stream to raw PCM, then encodes that PCM using the ALAC codec into the M4A container. No video codec or subtitle streams are carried into ALAC/M4A, and WebM's multiple audio track support collapses to a single track in the output (by default, FFmpeg selects the best audio stream). WebM's transparency and HDR features are irrelevant to audio-only output. Metadata tags (artist, title, album) embedded in the WebM file are generally mapped to equivalent M4A/iTunes atoms by FFmpeg, but field support varies — always verify critical metadata after conversion. There are no audio quality settings for ALAC since it is, by definition, lossless; the output bitrate is determined entirely by the complexity of the audio content, not by a user-selectable parameter.