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WebM

WebM is Google's royalty-free web video container using VP9 or AV1 with Opus audio.

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What is a WebM file?

An open, royalty-free container built for HTML5 video, pairing VP8, VP9 or AV1 video with Vorbis or Opus audio.

Technical characteristics

Representation
binary
Compression
VP8, VP9, AV1
Lossy
Yes
Transparency
Yes
Open specification
Yes

History and origin

Introduced
2010
Created by
Google

Compatibility

  • Windowsfull
  • macOSfull
  • Linuxfull
  • Androidfull
  • iOSpartial

Browsers: Chrome, Firefox, Edge, Safari 14.1+.

Advantages of WebM

  • Royalty-free
  • Smaller than H.264 at equal quality
  • Supports alpha-channel video

Limitations to know about

  • Weaker support in editing suites and consumer hardware
  • Slower encoding

When to use WebM

  • HTML5 video
  • Animated GIF replacements
  • Web backgrounds

Convert WebM files

WebM scores

Deterministic scores calculated from the structured facts above. Identical facts always produce identical scores.

Overall score

74/100

  • Web score

    94
    • browsers render it natively, so no conversion step is needed at request time
    • every major browser engine renders it natively
    • smaller payloads mean less I/O and faster first paint
    • it compresses lossily, which produces much smaller files than lossless coding

    Confidence 76% · evidence coverage 92%

  • Streaming score

    92
    • lossy compression keeps the bitrate low enough to stream reliably
    • smaller payloads mean less I/O and faster first paint
    • it compresses lossily, which produces much smaller files than lossless coding
    • every major browser engine renders it natively

    Confidence 79% · evidence coverage 100%

  • Longevity score

    90
    • it is actively maintained and current
    • the specification is published openly
    • the specification is public, so a decoder can always be rebuilt
    • it sits at the centre of the format ecosystem, with many documented relationships

    Confidence 76% · evidence coverage 100%

  • Performance score

    88
    • smaller payloads mean less I/O and faster first paint
    • it compresses lossily, which produces much smaller files than lossless coding

    Confidence 71% · evidence coverage 100%

  • Archiving score

    87
    • the specification is public, so a decoder can always be rebuilt
    • the specification is published openly
    • it is actively maintained and current
    • an openly specified format can be implemented without a licence negotiation

    Confidence 77% · evidence coverage 89%

  • Openness score

    87
    • the specification is published openly
    • an openly specified format can be implemented without a licence negotiation

    Confidence 62% · evidence coverage 100%

  • Compatibility score

    83
    • every major browser engine renders it natively
    • Windows, macOS, Linux, Android and iOS all open it without extra software
    • an open specification means cloud SDKs can implement it without licensing friction
    • it opens by double-clicking on every mainstream device
    • only a narrow set of applications handles it

    Confidence 80% · evidence coverage 100%

  • AI score

    66
    • the specification is published openly
    • smaller payloads mean less I/O and faster first paint
    • only a narrow set of applications handles it
    • lossy artefacts add noise that models can learn by mistake

    Confidence 59% · evidence coverage 100%

  • Photography score

    42
    • it opens by double-clicking on every mainstream device
    • it compresses lossily, which produces much smaller files than lossless coding
    • each edit-and-save cycle compounds compression damage

    Confidence 65% · evidence coverage 44%

  • Editing score

    13
    • each edit-and-save cycle compounds compression damage
    • only a narrow set of applications handles it

    Confidence 54% · evidence coverage 63%

  • Printing score

    8
    • lossy artefacts become visible when the image is enlarged for print
    • only a narrow set of applications handles it

    Confidence 63% · evidence coverage 50%

What WebM is recommended for

Every conclusion below is derived from the structured facts on this page — nothing is written by hand.

  • Browser compatibility100/100

    • Because every major browser engine renders it natively.
    • Because at least one shipping browser renders it.

  • Operating system compatibility100/100

    • Because Windows, macOS, Linux, Android and iOS all open it without extra software.
    • Because most platforms handle it natively.

  • Web suitability100/100

    • Because browsers render it natively, so no conversion step is needed at request time.
    • Because lossy compression keeps transfer sizes and Core Web Vitals in check.
    • Because the specification is open, so tooling and CDNs implement it freely.

  • Cloud compatibility100/100

    • Because an open specification means cloud SDKs can implement it without licensing friction.
    • Because it converts into many other formats, which suits automated pipelines.

  • Streaming100/100

    • Because lossy compression keeps the bitrate low enough to stream reliably.
    • Because browsers decode it natively, so it plays without a plugin.
    • Because open specifications avoid per-stream licensing complications.

  • Everyday consumer usage100/100

    • Because it opens by double-clicking on every mainstream device.
    • Because small files are easy to email, message and upload.
    • Because it is a current format that people and services still expect.

  • Open standards100/100

    • Because the specification is published openly.

  • Decode performance100/100

    • Because smaller payloads mean less I/O and faster first paint.
    • Because mature formats benefit from hardware and SIMD-optimised decoders.

  • Future-proofing100/100

    • Because it is actively maintained and current.
    • Because open specifications outlive the companies that create them.
    • Because nothing in the graph supersedes it yet.

  • Long-term archiving76/100

    • Because the specification is public, so a decoder can always be rebuilt.
    • Because it is a current, actively maintained format.
    • Because it has a decade or more of proven, stable implementations.

  • Popularity71/100

    • Because it sits at the centre of the format ecosystem, with many documented relationships.
    • Because every mainstream operating system handles it.
    • Because it is still current rather than being phased out.

  • Compression efficiency69/100

    • Because it compresses lossily, which produces much smaller files than lossless coding.
    • Because it defines a documented compression scheme.

What WebM is not recommended for

  • Printing suitability0/100

    • Because lossy artefacts become visible when the image is enlarged for print.
    • Because it does not satisfy: it is a page-description format built around fixed layout.

  • Professional editing0/100

    • Because each edit-and-save cycle compounds compression damage.
    • Because it does not satisfy: professional applications read and write it.

  • Software compatibility33/100

    • Because only a narrow set of applications handles it.

Related to WebM

File extensions

Media types

Created by

Compared with

Data quality

Every claim on this page is classified as a verified fact, a derived fact or an assumption.

Overall confidence
93%
Verification status
verified
Last reviewed
2026-08-03
Verified facts
2

2 classified claims backed by 1 source.

Sources and review status

Review status: verified · confidence 95%

Last reviewed 2026-08-03 (revision 1).