Step 1: Share your WebM files using the button above or by drag and drop.
Step 2: Click the 'Transform' button to start the transformation.
Step 3: Grab your converted MP4 files.
WebM to MP4 Transformation FAQ
How do I re-encode WebM to MP4 without losing video quality?
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Upload your WebM file and the converter runs a CRF-based re-encode targeting visually-lossless MP4 output (CRF 18 by default, lower values = larger file / higher quality). The codec is chosen to match the MP4 container — H.264 for broad-compat MP4, H.265 for size-efficient MKV, VP9 for WebM, AV1 for newer pipelines. WebM is deliberately narrow: VP8 or VP9 video (AV1 more recently) with Vorbis or Opus audio, and nothing else. Almost every MP4 in the wild is H.264 video with AAC audio; the container also legally holds HEVC, AV1 and VP9.
Both WebM and MP4 are modern containers — which should I actually keep?
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Keep whichever matches where the file is going, because neither is better in the abstract. One of these two is built for playback compatibility and the other for holding everything a file might contain, and they trade against each other exactly along that line. The pragmatic answer for most libraries is to archive in the feature-rich container and export to the compatible one on demand. WebM plays natively in every modern browser with no plugin, no licence fee and no patent exposure, which makes it the default for web-embedded video. MP4 is the safest possible delivery target — every phone, browser, console, editor and Smart TV built in the last decade plays it without extra software.
Which video codec does the MP4 output use?
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It depends on the MP4 container. MP4 defaults to H.264 for the broadest playback support across phones, browsers, and Smart TVs. MKV defaults to H.265 / HEVC for roughly half the file size at equivalent quality. WebM defaults to VP9. The advanced options expose explicit codec choice if you need to override. MP4 is ISO/IEC 14496-14, standardised in 2001 and derived from the same QuickTime box layout MOV uses.
Will my audio track survive WebM to MP4 conversion?
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Yes. When WebM and MP4 share an audio codec (e.g. both carry AAC), audio is re-muxed with no re-encode — bit-identical. When the codecs differ, audio is transcoded to AAC / Opus / Vorbis depending on what the MP4 container supports. Multi-track audio (commentary, alternate languages) is preserved.
Can I keep the original framerate when converting WebM to MP4?
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By default yes — a 24fps WebM stays 24fps in MP4; a 60fps WebM stays 60fps. If you need to change rate (e.g. interlaced 29.97 → progressive 30, or 60 → 30 for upload limits), the framerate option handles 3:2 pulldown, deinterlacing, and frame-blending in the same encode pass.
How much will the file size change going from WebM to MP4?
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Same-codec re-mux (WebM H.264 → MP4 H.264 just changing container): nearly identical size. Codec change can swing dramatically: H.264 → H.265 typically halves the file at the same visual quality; VP9 is roughly comparable; AV1 cuts another 20-30% but is slower to encode.
Will the MP4 file play on iPhone, Android, and Smart TVs?
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MP4 / H.264 plays natively on every modern device. MOV / H.264 plays on Apple devices and most TVs but not always on older Android. MKV needs VLC on iOS. WebM is browser-first. The advanced options include a "device compatibility" preset that picks the safest MP4 codec / container for your target. MP4 only supports one widely-honoured subtitle format (mov_text), and multi-track audio is unreliable outside desktop players.
How long does converting a 1-hour WebM video to MP4 take?
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Same-codec re-mux is near-instant — 30 to 60 seconds for a 1-hour file. A full codec re-encode runs at roughly 0.3-0.7x source duration on our GPU pipeline, so a 1-hour WebM → MP4 finishes in 18-40 minutes depending on resolution and target codec.
What is the maximum resolution supported for WebM to MP4?
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Up to 8K (7680×4320) on Premium plans. Free conversions are capped at 4K (3840×2160) by the per-file size limit. HDR metadata (HDR10, HDR10+, Dolby Vision when present) is carried through where both WebM and MP4 containers support it.
Is my WebM video private during conversion to MP4?
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Yes. Uploaded video files are processed in isolated workers, never viewed by a human, never indexed, and deleted within minutes of completion. The retention window is documented at /privacy/ and we publish no training corpus from user uploads.
Can I crop, trim, or rotate during the WebM to MP4 conversion?
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Not in the same step — use /video-trim/ or /video-cutter/ to clip first, then run the WebM → MP4 conversion. Chaining trim and convert is faster than re-encoding the entire WebM just to drop unused footage.
Why is the MP4 file blurry compared to the WebM source?
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Almost always a bitrate-too-low setting. Re-encoding from a high-bitrate WebM into a default-CRF MP4 compresses heavily on motion-rich scenes. Push CRF down to 16-18, or set an explicit target bitrate matched to the WebM source, and the MP4 regains its clarity.
