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Need help?How to Convert WebM to AMR Online
- Upload Your WebM File: Drag and drop one or more.webm files, or click "+ Add Files" to browse. The audio track is extracted from the WebM container — Vorbis or Opus audio inside the WebM is decoded and re-encoded to AMR-NB. Batch is supported.
- Pick Quality Preset and Constant Bitrate: AMR-NB only ships eight legal bitrates (4.75, 5.15, 5.90, 6.70, 7.40, 7.95, 10.2, 12.2 kbit/s). Leave Quality Preset on "Highest" to pin 12.2 kbit/s for the clearest speech, drop to "Low" or "Lowest" for the smallest.amr files (around 35-50 KB per minute at 4.75 kbit/s), or pick a specific value in the Constant Bitrate dropdown.
- Set Audio Channel, Sample Rate, and Trim (Optional): AMR-NB is fixed at mono 8000 Hz — those defaults are correct and you should not change them. Use Trim to cut a clip down to just the voice you want; AMR is a poor archival format, so keep only the seconds that matter.
- Convert and Download: Click Convert. Files are uploaded over an encrypted connection, processed on our servers, and deleted automatically after a few hours — no sign-up, no watermark, never shared.
Why Convert WebM to AMR?
WebM is Google's open container, introduced May 18, 2010, that wraps VP8/VP9 video with Vorbis or Opus audio. AMR (Adaptive Multi-Rate Narrowband) is a 3GPP speech codec standardized in the late 1990s that compresses voice to 4.75-12.2 kbit/s at an 8 kHz sample rate covering the 200-3400 Hz telephony band. You are intentionally throwing away music quality to land on a tiny, narrowband, mobile-network speech format. That trade-off only makes sense for specific jobs:
- Voice memo libraries on legacy Android devices. AMR was the original default capture format for Android's built-in voice recorder, so older handsets, in-car infotainment units, and feature phones often expect.amr rather than.m4a or.mp3.
- Telephony / IVR prompts. PBX systems, GSM/UMTS network gear, and old VoIP test rigs accept AMR-NB natively because it is the codec carried on the wire — no transcoding hop in the dial plan.
- Cheap MMS-style attachments. A one-minute spoken WebM clip from a meeting or podcast becomes roughly 35-90 KB as AMR (depending on bitrate), small enough to drop into SMS gateways, ticket systems, or 2G-era device profiles.
- Forensic and legal hand-offs. Court evidence intake portals and police body-cam pipelines still accept.amr because it is unambiguous, single-codec, single-rate, and trivially playable on departmental hardware.
- Embedded device firmware (IoT, alarms, kiosks). Doorbells, intercoms, and industrial alarm panels often ship with an AMR decoder only — pushing them a 16 KB greeting prompt is the path of least resistance.
- Long-form speech archives where size dominates quality. 24 hours of dictation at 4.75 kbit/s is under 55 MB, versus ~430 MB for the same audio as 40 kbit/s Opus.
If you actually want listenable speech for podcasts, audiobooks, or sharing in modern messaging apps, convert to MP3, WAV, M4A, or AAC instead — AMR-NB is the wrong codec for anything you want to listen to on headphones.
WebM Audio vs AMR — Format Comparison
| Property | WebM (Vorbis/Opus) | AMR-NB |
|---|---|---|
| Container | Matroska-based WebM | Raw.amr (or.3gp wrapper) |
| Codec(s) inside | Vorbis or Opus | Adaptive Multi-Rate Narrowband only |
| Standardized by | Google / On2 / Xiph (May 2010) | 3GPP (TS 26.071, late 1990s) |
| Sample rate | Up to 48 kHz | Fixed 8 kHz |
| Frequency response | Full-band, ~20 Hz-20 kHz | 200-3400 Hz (telephony band) |
| Channels | Mono / stereo / surround | Mono only |
| Typical bitrate | 64-510 kbit/s (Opus/Vorbis) | 4.75-12.2 kbit/s |
| Best for | Web video/audio, music, streaming | Mobile voice memos, IVR, GSM telephony |
| Royalty | Royalty-free | Patented — encoders licensed via VoiceAge |
| Modern device support | All major browsers, most players | Most Android, VLC, ffmpeg; iOS playback varies |
AMR-NB Bitrate Quick Guide
| Mode | Bitrate | ~Size per minute | Use when |
|---|---|---|---|
| MR475 | 4.75 kbit/s | ~36 KB | Lowest size; speech still intelligible but noticeably degraded |
| MR590 | 5.90 kbit/s | ~44 KB | GSM half-rate fallback; very small archives |
| MR740 | 7.40 kbit/s | ~56 KB | US-TDMA legacy; reasonable speech |
| MR795 | 7.95 kbit/s | ~60 KB | Common default on older Android voice recorders |
| MR102 | 10.2 kbit/s | ~77 KB | Noticeably cleaner; minor file-size cost |
| MR122 | 12.2 kbit/s | ~92 KB | "Highest" preset; GSM full-rate equivalent (EFR) |
Frequently Asked Questions
Why does my AMR file sound muffled and tinny compared to the WebM original?
That is the codec working as designed. AMR-NB only encodes the 200-3400 Hz band — the same band a 1990s GSM phone call used — so anything above 3.4 kHz (sibilance, music, room ambience) is filtered out before encoding. If the muffling is unacceptable, AMR-NB is the wrong target. Convert to MP3, Opus (WebM is already Opus or Vorbis), or AAC instead.
Will my iPhone play the AMR file I just made?
Not natively in Files or Music in current iOS versions. iPhones used to embed AMR support for MMS voice clips, but modern iOS playback is inconsistent — VLC for iOS and most third-party audio apps will play.amr, the stock Music app generally will not. If you need iPhone-friendly speech audio, convert WebM to M4A (AAC) instead.
Can I get AMR-WB (wideband, 16 kHz) output instead of narrowband?
This page outputs AMR-NB (the.amr extension, 8 kHz, eight bitrates up to 12.2 kbit/s). AMR-WB uses a different file extension (.awb) and the 50-7000 Hz wideband range — it is a separate format target. Use AMR-WB only when the receiving device specifically asks for it; otherwise AMR-NB is what "AMR" means in the wild.
What bitrate should I pick for voice notes?
For voice notes you actually want to understand later, pick 12.2 kbit/s ("Highest" preset). The file is still roughly 92 KB per minute, which is trivial. Only drop to 4.75-7.40 kbit/s if you are bulk-archiving hundreds of hours and the storage cost matters more than clarity.
Why is my WebM stereo but the AMR comes out mono?
AMR-NB is mono-only by spec. The encoder downmixes the WebM's left and right channels into a single channel before encoding — there is no stereo AMR mode to choose. If preserving stereo matters (music, binaural recording, two-mic interview), use WAV, MP3, or M4A as your target instead.
Does the WebM need to have an audio track? What if it is video-only?
The WebM must contain an audio track. Video-only WebM files (rare — usually screen captures with no microphone input) will fail to produce a usable AMR. If you have a silent WebM and need a placeholder, record fresh audio first.
How small can a one-hour speech recording get as AMR?
At the lowest bitrate (4.75 kbit/s, mono, 8 kHz), one hour is roughly 2.1 MB. At the highest (12.2 kbit/s) it is roughly 5.5 MB. Compare to a typical Opus podcast at 40 kbit/s stereo, which would be about 18 MB for the same hour — the AMR is 3-9x smaller, with the trade-off being phone-call audio quality.
Can I trim the WebM to just the speech I need before converting?
Yes — use the Trim control in Advanced Options to set a start time and duration, or pre-trim the WebM with the Video Cutter. Trimming first is the right move for AMR because the format is meant for short voice clips, not full-length media.
How do I do the reverse — AMR back to a normal format?
Use AMR to MP3. Reversing the conversion will not restore the audio quality lost when downsampling to 8 kHz mono — the high-frequency content is gone for good — but it will produce a file that plays in every modern app and device.