Convert WebM to AAC Online
Convert audio from WebM files to AAC for iPhone, iPad, Apple Music, podcasts, and the Apple ecosystem. Free, in your browser.
.webm · up to 100 MB
What you can do
WebM to AAC: web recordings ready for iPhone and Apple Music
Full Apple ecosystem
M4A/AAC works natively on iPhone, iPad, Mac, Apple Music, iTunes, and Apple Podcasts.
Podcasts ready to publish
AAC at 128 kbps meets Apple Podcasts Connect and Spotify for Podcasters requirements.
100% private
Your WebM never leaves your device. FFmpeg.wasm processes everything locally in the browser.
Video call recordings
Extract audio from Meet, Jitsi, and other platform recordings to AAC for Apple.
How it works
Three steps, no hassle
Upload your WebM file
Drag or select your .webm with Opus or Vorbis audio. Up to 500 MB, no signup.
Transcoding to AAC
FFmpeg.wasm decodes Opus or Vorbis audio from the WebM to PCM and re-encodes it to AAC-LC in an M4A container. Adjust bitrate by use: 64 kbps for voice, 192–256 kbps for music.
Download your AAC
M4A/AAC file ready for iPhone, Apple Music, podcasts on Apple Podcasts or Spotify, and any device. Download with one click.
FAQ
Got questions?
Browser recordings in WebM with Opus or Vorbis are excellent for web use (Chrome, Firefox, Edge play them natively), but have limited compatibility in the Apple ecosystem: iOS/iPadOS doesn't play WebM without third-party apps, Apple Music doesn't import WebM, and podcast distribution platforms (Apple Podcasts, Spotify) don't accept WebM as a delivery format. Converting to AAC in M4A solves all these problems: M4A/AAC is Apple's native format, playable on any Apple device without additional apps.
Opus to AAC is a transcoding between two lossy codecs, meaning there are two generations of loss. However, if the original WebM recording has Opus at a high bitrate (128 kbps or more), and you convert to AAC at 192–256 kbps, the difference is practically imperceptible in normal listening. For voice audio (podcasts, interviews, video conferences), where recording bitrates are typically 32–128 kbps Opus, transcoding to AAC at 128 kbps produces quality fully adequate for distribution. For produced music, having the original lossless audio is ideal rather than transcoding between lossy formats.
Yes, if you meet the technical requirements. Apple Podcasts accepts AAC in M4A with the following minimum specifications: 128 kbps bitrate for voice episodes, 44.1 kHz or 48 kHz sample rate, and maximum episode size of 1000 MB. The M4A file this tool produces is compatible with these requirements. Make sure to select at least 128 kbps when converting to meet Apple Podcasts Connect quality guidelines.
The JavaScript MediaRecorder API, available in Chrome since version 47 (2015) and Firefox since version 25 (2013), allows recording microphone or system audio in the browser. The output format depends on the browser: Chrome uses WebM with Opus by default (since Chrome 74, 2019), Firefox also uses WebM with Opus. The recording is segmented into data chunks (by default every second) that are concatenated into the final Blob. The resulting WebM file has a Matroska structure with audio in SimpleBlock blocks of the A_OPUS track.
To be a ringtone on iPhone, the file needs to be in M4R format (which is identical to M4A but with .m4r extension) with a maximum duration of 30 seconds. You can rename the M4A to M4R and import it into iTunes/Finder. However, the tool produces standard M4A; ringtone conversion requires the additional step of renaming the extension and importing it via iTunes on macOS or Finder. AAC is the only format accepted for custom ringtones on iPhone.
AAC-LC (Low Complexity) is the standard, most compatible profile: accepted by Apple Podcasts, Spotify, iTunes, and all devices. Recommended for podcasts at 128 kbps stereo or 96 kbps mono. HE-AAC (High Efficiency AAC, also called aacPlus) uses Spectral Band Replication to double efficiency at low bitrates: excellent for voice streaming at 32–64 kbps, but not all legacy players decode it. AAC-ELD (Enhanced Low Delay) is designed for real-time communications (FaceTime, Teams) with minimum 15 ms latency, not for podcast distribution. For podcasts from browser WebM, use AAC-LC at 128 kbps: maximum compatibility and sufficient quality for voice.
Convert WebM to AAC: web recording audio for iPhone, Apple Music, and podcasts
Converting WebM to AAC is the bridge between the web audio recording ecosystem (where WebM with Opus or Vorbis is the de facto technical standard in Chromium-based browsers and Firefox) and the Apple distribution and consumption ecosystem, where AAC in M4A container is the native and indispensable format for any audio workflow within the Apple universe. The browser's MediaRecorder API, standardized by the W3C in the MediaStream Recording specification published as a W3C Recommendation in October 2021, produces WebM files with Opus audio by default in Chrome (since version 74, April 2019) and Firefox (since version 28, 2014). Opus (RFC 6716, IETF, September 2012) is an extraordinarily efficient audio codec supporting bitrates from 6 to 510 kbps in a single stream, with configurable latency from 2.5 ms to 60 ms per frame, and operates in two internal modes based on detected content: SILK mode derived from the SILK codec developed by Skype for low-latency voice, and CELT mode based on the CELT codec developed by Xiph.Org for music and high-quality audio at higher bitrates. Despite Opus's undeniable technical excellence, the Apple ecosystem does not support it natively in any of its main applications or services in 2025: Safari on iOS, iPadOS, and macOS does not play WebM files natively, Apple Music does not accept WebM or Opus files directly as imports, and Apple Podcasts requires MP3 or AAC in M4A container for episode distribution to its millions of listeners worldwide. Conversion to AAC definitively and completely resolves all these compatibility issues with hardware and software in the Apple ecosystem.
The most frequent WebM to AAC workflows in 2025 involve four well-defined audio source categories. First category: meetings and video calls recorded in the web browser. Google Meet in Chrome produces WebM with Opus when the user activates local session recording. Jitsi Meet, BigBlueButton, and similar WebRTC applications also generate WebM with Opus as the default audio codec. To share audio from these meetings with iPhone users or publish it as an Apple Podcasts episode, conversion to AAC in M4A is the absolutely indispensable step that this tool makes straightforward. Second category: remote podcast recordings in the browser. Tools like Zencastr, Riverside.fm, and SquadCast record each participant's local audio in the browser as WebM, which is then combined in post-production for the final episode. Converting each participant's WebM to AAC allows working with them in GarageBand, Logic Pro, or Audio Hijack on Mac, where M4A is the preferred and most compatible import format. Third category: video tutorial and screencast narration. Chrome extensions like Loom, Screencastify, and Chrome DevTools' native capture produce WebM with the narrator's voice track embedded. Extracting that voice to AAC allows inserting it directly into Final Cut Pro or iMovie projects on Mac. Fourth category: audio samples for Apple Music and digital distribution. Live performance recordings or demos in WebM converted to AAC at 256 kbps for DistroKid, TuneCore, or CD Baby. All four categories share the same fundamental problem: WebM with Opus is not natively playable or distributable within the Apple ecosystem, and AAC in M4A is the single universal solution that resolves compatibility across every Apple device, service, and distribution platform simultaneously.
Convertir.ai runs WebM to AAC conversion entirely in the browser using FFmpeg.wasm. The processing flow begins with analysis of the WebM's EBML header to confirm DocType webm and the Matroska schema version in use. The audio track is identified in the Tracks block by TrackType=2 in the TrackEntry element. The CodecID in TrackEntry determines the decoder to use: for A_OPUS, FFmpeg uses the libopus decoder that processes Opus packets extracted from the Matroska SimpleBlocks, producing 32-bit float PCM at 48 kHz which is the standard internal sample rate of the Opus codec regardless of the original recording frequency. For A_VORBIS, FFmpeg uses libvorbis to decode Vorbis packets to float PCM at the stream's native sample rate. The resulting PCM passes through FFmpeg's SWR resampler if needed to adapt the sample rate to the desired AAC output (Opus works at 48 kHz, while AAC-LC in M4A can use 44.1 kHz or 48 kHz depending on the chosen configuration). The AAC encoder in FFmpeg, which includes the native aac encoder and the high-quality FDK-AAC encoder with the libfdk_aac library if compiled, compresses the PCM to the bitrate selected by the user. The output M4A uses the MPEG-4 Part 14 container with standard atoms: ftyp indicating M4A, moov with metadata including mvhd for global duration, trak with tkhd and mdia and minf and stbl and stsd with the mp4a atom describing the complete AAC-LC configuration, and mdat for the AAC-encoded audio data. WebM metadata such as title, artist, and creation date is transferred to the M4A's ilst atoms for full compatibility with iTunes and Apple Music across all Apple devices.