Imagyc›Articles

Video codecs explained: H.264, HEVC, VP9 and AV1

Published October 13, 2026 · 3 min read

H.264 is a conservative starting point for sharing videos across many devices. HEVC can suit efficient high-resolution storage when the destination supports it. VP9 and AV1 are important web-distribution options. The best choice depends on playback requirements and the encoder settings.

A codec is not a file extension. MP4 can contain H.264, HEVC or AV1, so knowing that a file is MP4 does not settle a compatibility problem.

What does a video codec do?

An encoder turns pictures into a data stream. A decoder reconstructs pictures for playback. Lossy compression discards some information to reduce the size.

A container, such as MP4, MOV, MKV or WebM, organizes the tracks. The video formats guide explains containers; this guide focuses on the picture's encoding.

A practical comparison

These are use-case guidelines, not a promise of identical performance on every file.

H.264 for compatibility

H.264 is also known as AVC and is used across many video workflows. ¹ MP4 with H.264 video and AAC audio is a practical combination for everyday delivery.

Profiles, levels and encoding settings still matter. A demanding file can fail on an older device even when its codec name is familiar.

HEVC for supported high-resolution workflows

HEVC stands for High Efficiency Video Coding and is also called H.265. ² It is common in high-resolution recordings, including iPhone capture modes.

Changing MOV to MP4 does not solve missing HEVC support. The iPhone video on Windows guide explains when a decoder lets you keep the original and when re-encoding is needed.

VP9 for web distribution

VP9 is a codec from the WebM Project. ³ It appears in online distribution and can be paired with compatible containers such as WebM.

Test the devices your audience uses. Hardware acceleration and browser support can affect smooth playback and battery use.

AV1 for efficient supported delivery

AV1 is an open codec developed by the Alliance for Open Media for efficient compression. ⁴ It can suit distribution that benefits from lower data transfer and accepts the format.

A device that can play AV1 is not necessarily able to encode it quickly. Encoding and decoding are different tasks. Support depends on hardware and software; an updated browser does not automatically make every device compatible. ⁵

Does a newer codec always create a smaller file?

No. Source content, encoder, settings, resolution and target quality affect the result. Comparing unrelated files cannot establish codec efficiency.

At the same average bitrate and duration, sizes will tend to be similar across codecs. An efficient codec's benefit is reaching a desired quality with fewer data, when the settings allow it.

As a calculated example, one minute of video at 3 Mbps contains about 22.5 MB of picture data alone. Audio and container overhead add more. A “4K” resolution label cannot determine the file size by itself.

Choose and test an output

1. Identify the receiving app or device.
2. Check the codecs it accepts.
3. Choose an original sample with motion and fine detail.
4. Open the video converter for supported saved files.
5. Choose an available output and inspect the codec actually produced.
6. Compare playback, picture, sound and size before processing everything.

Imagyc works in your browser without uploading the file. Do not assume every codec discussed here is available as an output on every device.

For a missing Windows decoder, Microsoft documents extensions for formats including HEVC, VP9 and AV1. ⁶ Adding support can let you watch the original rather than convert it.

Frequently asked questions

Is MP4 a codec?

No. It is a container that can hold differently encoded tracks.

Is AV1 always better than H.264?

Not for every task. Compatibility, speed and editing needs can make H.264 more suitable.

Does HEVC conversion guarantee a smaller file?

No. The source and settings determine the result. Check actual size and picture quality.

Can I change codecs without losing anything?

Ordinary lossy re-encoding does not create an identical copy. Keep the source or copy compatible encoded tracks without re-encoding when preservation is required.