Technology

WebM vs MP4 for Web: The Developer's Guide (2026)

Ryan Trann

December 9, 2025

5 min read

Choosing the best video format for web apps is complicated. But for optimized video delivery (non streaming) you've really only got a couple choices:

MP4 and WebM.

They're both viable but there are tradeoffs to consider. This is a guide to help you figure it out.

Containers vs Codecs: The Short Version

Containers (MP4, WebM, MOV) are wrappers.
Codecs (H.264, VP9, AV1) are the compression algorithms.

Containers decide compatibility.
Codecs decide size and quality.

Most devices, from iPhones to Android phones to action cameras, record in MP4 or MOV variants. These are fine as inputs. The delivery format is what actually matters here.

The Formats That Matter Today

Despite the sea of video formats, modern video delivery revolves around three (excluding streaming). For the web, browser compatibility is king. A common question we see often is: Does Safari support WebM? The answer in 2026 is finally yes (mostly):

Format	Codec	Compatibility	File Size	Notes
MP4	H.264	Universal support across all browsers and devices	Larger than WebM but smaller than the original	Safe default; works everywhere
WebM	VP9	Recently baseline on caniuse. Safari support reliable on latest devices	Smaller (25–50% less than MP4)	Open source, efficient, rapidly becoming the new default
WebM	AV1	Growing support but Safari is behind	Smallest	Likely the future, not widely usable yet

MP4 / H.264

Compatibility

Universal support across all browsers and devices

File Size

Larger than WebM but smaller than the original

Notes

Safe default; works everywhere

WebM / VP9

Compatibility

Recently baseline on caniuse. Safari support reliable on latest devices

File Size

Smaller (25–50% less than MP4)

Notes

Open source, efficient, rapidly becoming the new default

WebM / AV1

Compatibility

Growing support but Safari is behind

File Size

Smallest

Notes

Likely the future, not widely usable yet

Real-World Size Differences: AV1 vs VP9 vs H.264

A typical iPhone upload (~180MB MOV, HEVC) becomes:

Output	Approximate Size
MP4 (H.264)	~25–30MB
WebM (VP9)	~15–18MB
WebM (AV1)	~12–15MB

Those savings scale fast as your traffic grows.

Why We Prioritize MP4 vs WebM For Default Delivery Right Now

We aim to deliver the best format available that balances compression, quality, and universal compatibility.

Today, MP4 is still the only format that plays everywhere without exceptions, especially in Safari, embedded browsers, and older devices. But that landscape is changing.

WebM (VP9) recently reached baseline support on caniuse, meaning it is supported on all major browsers with recent devices.

Because of this Hyperserve will shift to WebM as the primary delivery format once real world stability is confirmed. MP4 will remain available for compatibility, but the goal is to deliver the best option currently available without developers needing to think about it.

What You Should Use Today

Goal	Format
Maximum reliability	MP4
Smaller files & modern compression	WebM (with MP4 fallback when needed)
Minimal complexity	Use Hyperserve's default

Conclusion

The video landscape is finally shifting. MP4 has been the universal standard for over a decade and remains the safest choice today. But WebM has now reached a real tipping point: significantly smaller files and broad browser support, including Safari, make it the first serious contender to replace MP4.

At this point it's mainly older iOS devices holding back a full transition.

Hyperserve's goal is to spare developers from tracking browser quirks or codec trends. We always deliver the best mix of compression, quality, and compatibility starting with MP4 today and transitioning to WebM as it proves stable across real world usage.

You shouldn't have to care about codecs. You should just get fast, reliable video delivery. Hyperserve's job is to make that the default.