WebM vs MP4: Which Video Format for the Web?

The Web Video Format Decision

If you are embedding video on a website, you face a fundamental choice: WebM or MP4? Both formats deliver high-quality video in web browsers, but they come from different philosophies, use different codecs, and have different trade-offs in compatibility, file size, and encoding complexity.

MP4 (with H.264 video) is the safe, universal choice — it plays everywhere. WebM (with VP9 or AV1 video) is the technically superior choice — it produces smaller files at the same quality. Understanding when each format makes sense is the key to making the right decision for your specific use case.

Head-to-Head Comparison

Codec Comparison: VP9 vs. H.264 vs. AV1

The container (WebM vs. MP4) matters less than the codec inside it. Here is how the video codecs compare:

H.264 (AVC) — The Universal Standard

• Plays on every browser, device, and platform
• Hardware encoding and decoding on all GPUs (2010+)
• Fast encoding — real-time is easy
• Good compression, but showing its age (standardized 2003)
• Patent-encumbered (MPEG LA pool, free for end users)

VP9 — Google's Open-Source Answer

• 30-40% better compression than H.264 at equivalent quality
• Hardware decode on most modern devices (2015+)
• Used by YouTube for most video delivery
• Encoding is 5-10x slower than H.264
• Royalty-free (Google patent pledge)

AV1 — The Next Generation

• 30-50% better compression than VP9
• Developed by the Alliance for Open Media (Google, Netflix, Mozilla, Apple, etc.)
• Hardware decode on GPUs from 2020+ (Intel 11th gen, NVIDIA RTX 30+, Apple M3+)
• Encoding is extremely slow (10-50x slower than H.264)
• Royalty-free
• Works in both WebM AND MP4 containers

File Size Comparison

For a 1080p, 10-minute video at equivalent visual quality:

The savings are significant. For a video-heavy website serving terabytes of content monthly, the bandwidth cost difference between H.264 and VP9 is substantial.

Browser Compatibility (2026)

The critical gap: Safari on iOS does not support VP9 WebM. If your audience includes iPhone users (which it almost certainly does), serving WebM as your only format means broken video for a significant portion of visitors.

Practical Recommendations

Use MP4 (H.264) When:

• You need universal compatibility with zero fallback complexity
• Your video content is user-generated (fast encoding matters)
• Your audience includes iOS/Safari users
• You are embedding video in email, PowerPoint, or non-web contexts
• You want hardware-accelerated encoding for real-time or near-real-time workflows

Use WebM (VP9) When:

• Bandwidth cost is a primary concern
• You can serve MP4 as a fallback for Safari/iOS
• You are pre-encoding content (encoding speed does not matter)
• Your audience is primarily Chrome/Firefox/Android
• You want royalty-free codecs for legal simplicity

Use Both (Best Practice for Web):

<video controls>
  <source src="video.webm" type="video/webm" />
  <source src="video.mp4" type="video/mp4" />
</video>

The browser picks the first format it supports. Chrome and Firefox will load the WebM (smaller file), while Safari falls back to MP4.

The AV1 Future:

AV1 in MP4 containers is increasingly the best of both worlds — excellent compression with broad compatibility. As hardware decode support expands (most new devices since 2022 support it), AV1/MP4 may become the single-format answer.

Encoding Examples

H.264 MP4 (Fast, Compatible)

ffmpeg -i source.mp4 -c:v libx264 -crf 23 -preset medium \
  -c:a aac -b:a 128k -movflags +faststart output.mp4

VP9 WebM (Smaller, Slower)

ffmpeg -i source.mp4 -c:v libvpx-vp9 -crf 31 -b:v 0 \
  -row-mt 1 -c:a libopus -b:a 128k output.webm

AV1 MP4 (Smallest, Slowest)

ffmpeg -i source.mp4 -c:v libaom-av1 -crf 30 -cpu-used 4 \
  -row-mt 1 -c:a libopus -b:a 128k output.mp4

For more on video encoding settings, see our video codecs explained guide and our H.265 vs H.264 vs AV1 comparison.

Streaming Considerations

For adaptive bitrate streaming (ABR), both formats work with DASH (Dynamic Adaptive Streaming over HTTP). MP4 also works with HLS (HTTP Live Streaming), which is Apple's preferred protocol and has the widest CDN support.

If you use HLS for video delivery (common for live streaming and Apple-focused delivery), MP4 is your only option.

Conclusion

For web video in 2026, the practical answer is: serve WebM (VP9) with MP4 (H.264) fallback for maximum quality and compatibility. If maintaining two encodes is too complex, MP4 with H.264 is the safe single-format choice. If you can invest in slow encoding, AV1 in MP4 offers the best compression with broad compatibility — and it makes the WebM vs. MP4 container debate irrelevant.

Need to convert? Try our free WebM to MP4 converter or MP4 to WebM converter — no registration required.