MyMediaTools

Convert WebM to 3GPP — Free Online Tool

Convert WebM files to 3GPP format (.3gp) for playback on legacy mobile devices and 3G-era phones. This tool re-encodes VP9 video to H.264 and Opus/Vorbis audio to AAC — codecs natively supported by 3GPP-compliant handsets — entirely in your browser with no file uploads.

FFmpeg Command

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Estimated output:

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How It Works

WebM and 3GPP are fundamentally incompatible containers that share no codecs, so this conversion requires full re-encoding of every stream. The VP9 video track is decoded and re-encoded using the H.264 (libx264) codec at CRF 23, a visually transparent quality level suitable for mobile screens. The Opus or Vorbis audio track is decoded and re-encoded as AAC at 64k bitrate — the standard choice for 3GPP audio given the format's low-bandwidth mobile heritage. The -movflags +faststart flag reorganizes the output file's metadata to the front, enabling progressive download and streaming playback on mobile networks before the file has fully downloaded.

What Each Flag Does

Flag What it does
ffmpeg Invokes the FFmpeg program — the open-source multimedia processing engine that performs all decoding, re-encoding, and container muxing. On this web page, FFmpeg runs as a WebAssembly binary (FFmpeg.wasm) inside your browser, so no software installation is needed.
-i input.webm Specifies the input file in WebM format. FFmpeg will detect the container and identify the VP9 video stream and Opus or Vorbis audio stream inside it, both of which require full re-encoding since neither codec is supported by the 3GPP container.
-c:v libx264 Selects H.264 (via the libx264 encoder) as the output video codec. H.264 is the standard video codec for 3GPP and is universally supported by 3G-era mobile devices and modern smartphones alike. This replaces the input's VP9 stream, which 3GP cannot carry.
-c:a aac Selects AAC as the output audio codec, replacing the WebM file's Opus or Vorbis audio track. AAC is the primary audio codec specified by the 3GPP standard and is supported by virtually all mobile devices that handle 3GP video.
-crf 23 Sets the Constant Rate Factor for H.264 encoding to 23, the libx264 default. This is a quality-based variable bitrate setting where lower values mean better quality and larger files; CRF 23 strikes a balance between visual quality and file size appropriate for mobile screens.
-b:a 64k Sets the AAC audio bitrate to 64 kilobits per second, reflecting 3GPP's mobile-first heritage where low audio bitrates were necessary for delivery over 3G networks. This is noticeably lower than typical WebM audio bitrates but remains intelligible for voice and most music content.
-movflags +faststart Moves the MP4/3GP moov atom (the file's index and metadata block) to the beginning of the output file. This is critical for 3GP mobile streaming because it allows the device to begin playback while the file is still downloading, rather than waiting for the entire file to arrive.
output.3gp Specifies the output filename with the .3gp extension, which tells FFmpeg to wrap the H.264 video and AAC audio into a 3GPP-compliant container. The .3gp extension is recognized by mobile devices, MMS systems, and legacy media players as a 3GPP file.

Common Use Cases

  • Sharing video clips with contacts using older Nokia, Samsung, or Sony Ericsson feature phones that only support 3GP video playback
  • Uploading video to mobile video portals or MMS systems that mandate 3GP container format for 3G network delivery
  • Archiving web video content captured in WebM format into a format readable by legacy mobile media players and embedded device firmware
  • Compressing a WebM screen recording or tutorial video into the low-bitrate 3GP format to minimize file size for distribution over slow mobile connections
  • Testing how a WebM video asset will render when transcoded through a mobile carrier's automatic format conversion pipeline that outputs 3GP
  • Preparing video content for older in-vehicle infotainment systems or handheld GPS devices that accept 3GP but not WebM

Frequently Asked Questions

Yes — this is a lossy-to-lossy transcoding, so some generation loss is unavoidable. VP9 in WebM is highly efficient, and re-encoding its decoded frames into H.264 at CRF 23 introduces compression artifacts specific to H.264. For most mobile-sized video at typical resolutions (480p or below), the quality difference is minimal and acceptable. If your source WebM was already heavily compressed, the quality degradation will be more noticeable.
No. 3GPP does not support alpha channel transparency or HDR metadata. If your WebM file contains a VP9 video track with alpha (transparency), that alpha layer will be discarded during conversion and the output will be fully opaque. HDR color information encoded in the WebM will also be lost, as H.264 in 3GP targets standard dynamic range display profiles typical of mobile screens.
The default audio bitrate for 3GP output is 64k AAC, compared to typical Opus or Vorbis tracks in WebM which are often encoded at 128k or higher. This is intentional — 3GPP was standardized for 3G mobile networks where bandwidth is scarce, so low audio bitrates are the norm. If your use case allows higher audio quality, you can adjust the -b:a flag in the FFmpeg command to 96k or 128k, though keep in mind this will make the file less compatible with the most constrained 3G devices.
No. WebM supports subtitles and chapters, but the 3GPP container format does not support either feature. Any subtitle tracks (WebVTT or otherwise) and chapter metadata embedded in the WebM source file will be silently dropped during conversion. If you need subtitles, you would need to burn them directly into the video frames using FFmpeg's subtitles filter before or during this conversion.
To adjust video quality, change the -crf value: lower numbers (e.g., -crf 18) produce higher quality and larger files, while higher numbers (e.g., -crf 28) produce smaller files with more compression. To resize the video for smaller mobile screens, add a scale filter such as -vf scale=320:-2 before the output filename, which scales the width to 320 pixels (a common 3GP resolution) while preserving the aspect ratio. For example: ffmpeg -i input.webm -c:v libx264 -c:a aac -crf 23 -b:a 64k -vf scale=320:-2 -movflags +faststart output.3gp
Yes, on a desktop you can batch process using a shell loop. On Linux or macOS: for f in *.webm; do ffmpeg -i "$f" -c:v libx264 -c:a aac -crf 23 -b:a 64k -movflags +faststart "${f%.webm}.3gp"; done — this iterates over every WebM file in the current directory and produces a matching 3GP file. On Windows Command Prompt: for %f in (*.webm) do ffmpeg -i "%f" -c:v libx264 -c:a aac -crf 23 -b:a 64k -movflags +faststart "%~nf.3gp". The in-browser tool processes one file at a time, so local FFmpeg is recommended for bulk jobs.

Technical Notes

WebM and 3GPP represent two different eras of video delivery — WebM is a modern, open-source format built for high-efficiency web streaming with VP9 or AV1 video, while 3GPP was standardized in the early 2000s to deliver video over constrained 3G mobile networks. Because the two formats share zero native codecs, every stream must be fully decoded and re-encoded, making this a computationally intensive conversion compared to remux-only jobs like MKV-to-MP4. The H.264 baseline or main profile produced by libx264 in a 3GP wrapper is broadly compatible across 3GPP-compliant devices, but very old handsets may impose resolution limits (typically 176×144 QCIF or 352×288 CIF). If targeting such devices, you should manually add a -vf scale=176:144 or similar constraint. Notably, 3GPP supports only a single audio track, so any multi-track audio in the WebM (e.g., multiple language dubs) will be reduced to the first audio stream only. No metadata fields from WebM (title, artist, description) are reliably mapped to 3GP atoms, so expect metadata loss. The -movflags +faststart flag is especially meaningful for 3GP delivery because it enables the file to begin playing during download over slow mobile connections, which was a core use case for the format.

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