Source: https://mactoolbox.app/glossary/h264

# What is H.264?

By Nikhil Barik · Published November 3, 2026

## Quick answer

H.264, also called AVC, is the most widely supported video codec. It plays on almost every device and website, at the cost of larger files than HEVC.

## What H.264 is

H.264 compresses video by storing only what changes between frames. It is usually found in MP4 and MOV files and is the default safe choice for sharing.

## Why it matters on a Mac

Every Mac, iPhone, browser and most TVs can play H.264. If a video will not play for someone you sent it to, re-encoding it as H.264 in an MP4 is the usual fix.

## How to check it on macOS

Open the video in QuickTime Player and choose Window > Show Movie Inspector to see the format. Media Info in Toolbox lists the codec of each video and audio track.

## How Toolbox handles it

Compress Video and Convert Video can encode with H.264 or HEVC. Convert Video can copy streams without re-encoding when the codecs already fit the new container, which is fast and loses no quality.

## Frequently asked questions

**Is H.264 the same as MP4?**

No. MP4 is a container. H.264 is one codec that can be stored inside it.

**Is H.264 or HEVC smaller?**

HEVC is about half the size at similar quality.

**Is H.264 lossy?**

Yes. Higher quality settings keep more detail but the file is larger.

## Tools mentioned

- [**Compress Video**: Shrink video files while keeping them looking great.](https://mactoolbox.app/compress-video-mac)
- [**Convert Video**: Change videos to MP4, MOV, WebM or M4V.](https://mactoolbox.app/convert-video-to-mp4-mac)
- [**Media Info**: See the codec, resolution, frame rate, bitrate and metadata of videos and audio.](https://mactoolbox.app/video-codec-info-mac)

## Keep reading

- [Compress Video](https://mactoolbox.app/compress-video-mac)
- [Convert Video](https://mactoolbox.app/convert-video-to-mp4-mac)
- [HEVC (H.265)](https://mactoolbox.app/glossary/hevc-h265)
- [Container format](https://mactoolbox.app/glossary/container-format)