MP4 to WebM Converter

How to Convert MP4 to WebM Online

1. Upload Your MP4 File: Drag and drop or click "Add Files" to select MP4 files. iPhone exports, GoPro recordings, screen captures, edited timeline renders, and downloaded clips all work. M4V is also accepted. Batch is supported — drop in an entire folder.
2. Pick a Codec and Quality: Default is VP9 (Google's modern web video codec). Choose AV1 for the smallest output on modern devices, or VP8 for legacy compatibility. Set a quality preset (Highest → Lowest), target a percentage of the original size or an exact size in MB, or fine-tune with CRF on the VP9/AV1 scale (18 = visually lossless, 30 = web default, 36 = small).
3. Resize or Trim: Pick a resolution preset (2160p / 1440p / 1080p / 720p / 480p / 360p), enter custom width × height, scale by percentage, or trim using start time + duration in HH:MM:SS.sss format. Audio re-encodes to Opus by default — switch to Vorbis if needed.
4. 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 MP4 to WebM?

MP4 is the universal video container — H.264 / H.265 video plus AAC audio inside an MPEG-4 wrapper, used by virtually every camera, phone, and editor since 2003. WebM (VP8 / VP9 / AV1 video, Opus / Vorbis audio) is the open-source format Google designed specifically for the modern web. WebM is smaller than MP4 at the same visual quality and is royalty-free for commercial use. Common reasons to convert MP4 → WebM:

• HTML5 <video> embedding — WebM is the de-facto format for self-hosted web video. Browsers prefer it, CDN bandwidth costs drop, and <source type="video/webm"> works in Chrome, Firefox, Edge, Opera, and Safari 14.1+. The standard pattern is WebM first, MP4 as fallback.
• 20-50% smaller files at the same quality — VP9 inside WebM is typically 30-50% smaller than H.264 inside MP4 at equivalent CRF. AV1 is even smaller. On a high-traffic site, that translates directly into bandwidth savings.
• Royalty-free codecs for commercial streaming — H.264 and H.265 are patent-encumbered (MPEG-LA / Access Advance pools). WebM (VP8 / VP9 / AV1) carries no licensing fees, which matters for paid platforms, ad-supported video, and embedded clips in commercial apps.
• Background hero videos and looping autoplay clips — Hero-section background videos and product loops need to be tiny so they autoplay before the rest of the page renders. WebM at low CRF is far better suited than MP4 for muted, silent autoplay loops.
• Self-hosting without YouTube — Product demos, tutorials, and portfolio reels load faster as WebM than as MP4. Pair with a CDN like Cloudflare R2 or Bunny.net and you bypass YouTube embeds entirely.
• Open-source and Linux-friendly tooling — Many open-source CMS plugins (WordPress, Ghost), static-site generators, and Linux video pipelines handle WebM natively without licensing dialog boxes.

MP4 vs WebM — Format Comparison

WebM Codec Choice for the Output

Frequently Asked Questions

Will Safari users be able to play the WebM?

Safari 14.1+ (macOS Big Sur and later, iOS 14.5+) plays WebM with VP9. Safari on macOS Sonoma added AV1 hardware decode for newer Macs. For older Safari versions, embed both formats in your <video> tag — WebM first, MP4 fallback second. Modern Safari picks the WebM; older Safari falls back to the original MP4. Keep the MP4 source around as the fallback.

How much smaller will the WebM be than the MP4?

For a typical 1080p H.264 MP4 re-encoded to VP9 WebM at the default preset, expect 30-50% smaller at visually equivalent quality. For 4K H.265 MP4 re-encoded to AV1 WebM, savings can reach 50-60%. The exact number depends on source bitrate — already-compressed MP4s see smaller savings than mastered files.

Should I pick VP9, AV1, or VP8?

VP9 for almost everything — universal modern browser support, 30-50% smaller than H.264, fast enough to encode in browser. AV1 for the smallest possible files when the audience is on 2022+ devices — encoding takes 5-10× longer but the file is roughly half the VP9 size. VP8 only for very old Android devices or extremely conservative legacy compatibility.

Will I lose quality converting MP4 to WebM?

A small re-encoding loss is unavoidable since H.264/H.265 (MP4) and VP9/AV1 (WebM) are different codecs — the source has to be decoded and re-encoded. At CRF 18-22 the difference is invisible in normal viewing. The default Highest preset produces near-source quality; lower presets trade visible compression for much smaller files.

Can I batch convert multiple MP4 files?

Yes — drop in a whole folder of clips, exports, or downloaded videos. They convert in parallel on our servers and download individually or as a single ZIP. Useful for converting a full course library, a portfolio's worth of reels, or a season of recorded streams in one pass.

Can I trim or cut while converting?

Yes. Use the trim section to enter a start time and duration. Both fields accept seconds (12.5) or HH:MM:SS.sss format (00:01:30.500). Trim first to skip intros, dead air, or unwanted footage — the encoder works on the trimmed range, so you save both file size and encoding time. For more control see Cut Video.

Will the audio survive the conversion?

Yes. MP4's AAC audio is re-encoded to Opus by default (the modern WebM standard) or Vorbis. Audio quality is preserved at typical bitrates — 96-128 kbps Opus is transparent for music and far better than 128 kbps AAC byte-for-byte. If your MP4 has multiple audio tracks (rare), the primary track is kept.

What's the file size limit?

XConvert handles large MP4 files including multi-GB 4K recordings and full-length screen captures. Files are uploaded over an encrypted connection, processed on our servers, and deleted automatically after a few hours — there is no fixed cap and no quantity limit on batch jobs. For very large sources, lowering resolution to 1080p first (Resize Video) speeds up the WebM encode considerably.

Need to go the other direction?

If you have WebM files that need to play on devices that don't support it (older iPhones, smart TVs, Premiere Pro), use WebM to MP4. For animated WebM clips destined for messaging apps or Slack, see WebM to GIF.