H.264 vs H.265 (AVC vs HEVC): Size, Support, Cost

Two generations of the same standards work

H.264, also called AVC (Advanced Video Coding), was finalized in 2003 by the ITU-T and ISO/IEC standards groups working together. It became the codec of web video, Blu-ray, video calls and most phone and camera recordings for over a decade.

H.265, or HEVC (High Efficiency Video Coding), came from the same groups and was finalized in 2013. Its goal was to cut bitrate substantially at the same quality, driven by the arrival of 4K screens and the cost of streaming. Both are lossy, both compress across frames, and both use the same broad toolkit: predicting each block from nearby pixels or from other frames and encoding only the difference. The general mechanics are explained in what a video codec is.

Where the efficiency comes from

HEVC gets its savings from more flexible tools rather than a new principle:

Larger and more adaptable blocks. H.264 works in macroblocks of 16 by 16 pixels; HEVC uses coding tree units of up to 64 by 64 that subdivide as needed, which suits large smooth areas in high-resolution footage.
More prediction directions within a frame, so detail can be predicted from neighbors more precisely.
Improved motion prediction and filtering that reduce the data needed to describe movement and clean up block edges.

The gain is often summarized as similar quality at around half the bitrate. Treat that as a best-case shorthand: the real saving depends on the encoder, its settings, the resolution and the content. It tends to be largest on high-resolution, slow-moving footage and smaller on low-resolution clips, where H.264 already does well.

Encoding cost and speed

More options mean more decisions for the encoder. In software, an HEVC encode at a careful preset can take several times longer than an H.264 encode of the same clip on the same machine. Hardware encoders in recent GPUs, laptops and phones make HEVC encoding fast, which is why phones can record it in real time, but hardware encoders generally trade some efficiency for speed.

Decoding is also heavier. A device with an HEVC hardware decoder plays it smoothly; a device without one decodes in software, which uses more power and can stutter on high-resolution files. The article on hardware video decoding explains how that support is built into chips and browsers.

Device and browser support

H.264: Plays on practically every browser, phone, TV, laptop, presentation tool and video platform. The default for maximum reach.
H.265 on phones: Recent phones decode it in hardware, and many record in it by default when set to a high-efficiency mode.
H.265 on computers: Common in hardware from recent years; older machines may lack a decoder, and some operating systems need an extension or app.
H.265 in browsers: Varies by browser, operating system and hardware, and has been changing. Check current support for your audience.
10-bit and HDR: HEVC's Main 10 profile is widely used for HDR video. H.264 has 10-bit profiles, but hardware support for them is rare.

The practical consequence is simple: an HEVC file you play without trouble on your own phone may fail on a colleague's older laptop or in a particular browser. If that is already happening to you, the troubleshooting steps live in HEVC compatibility; this page covers the choice before you export.

Licensing, briefly

Both codecs are covered by patents. H.264 licensing has been handled mainly through a single patent pool, and that relative simplicity helped it spread everywhere. HEVC licensing is split among several pools and individual patent holders, a fragmentation widely cited as one reason some browser makers were slow to support it and one motivation for royalty-free alternatives such as AV1.

For someone exporting video from an editor, this is mostly invisible: the editor, phone or operating system vendor handles licensing. If you are building software or hardware that encodes or decodes either codec, get current legal advice; licensing terms change and this is not legal advice.

Which to export for which destination

Embedding on a website, sending to people on unknown devices, or presenting from someone else's computer: H.264.
Uploading to a large video platform: either usually works, because platforms re-encode uploads. H.264 is the low-risk default; HEVC can make a large 4K upload smaller. Check the platform's current recommendations.
Archiving finished masters where storage matters: HEVC at a high quality setting saves space, provided you will still be able to decode it later. Some archives prefer higher-bitrate H.264 or an intermediate codec for longevity.
4K and HDR delivery to devices you know support it: HEVC.
Files that must go through email or chat size limits: HEVC can help, though cutting length or resolution often matters more; see video file too large.
Editing: neither is ideal for heavy editing, since inter-frame compression makes scrubbing and repeated exports demanding. Many editors work from proxies or intermediates and export a delivery codec at the end.

Hypothetical: a training team with mixed laptops

A company records training on recent phones, which save HEVC. The videos play fine for the production team but stutter or show a black picture on several older office laptops. The team keeps HEVC masters for storage and exports H.264 copies for the intranet, which every laptop plays.

Recording settings on phones

Many phones offer a choice between a high-efficiency mode, which records HEVC, and a most-compatible mode, which records H.264. High efficiency saves storage and is the usual default on recent iPhones. Most compatible is worth choosing when the footage will go straight to people or tools you do not control, such as a client who edits on an older system or a classroom projector computer.

Switching after the fact means re-encoding, which costs time and a little quality. If you know the destination in advance, record in the codec it needs.

Mistakes and trade-offs to watch

Converting existing H.264 files to HEVC purely to save space. Every re-encode loses a little, and a careless HEVC encode at a low bitrate can look worse than the original.
Judging efficiency from one test. A fast hardware HEVC encode and a slow software H.264 encode may end up closer in size than the shorthand suggests.
Sending HEVC to an audience you cannot see, then getting reports of black screens or audio-only playback.
Choosing HEVC for archives without checking that your future tools will decode it.
Forgetting that HDR footage needs an HDR-aware pipeline end to end. Converting HDR HEVC to H.264 without tone mapping can produce washed-out color.

What mydubly does with H.264 and H.265 video

mydubly's video translator accepts MP4, MOV, WebM, MKV and M4V files, including H.264 and HEVC video, provided your browser can read the file. It never re-encodes the picture. When you translate and dub a video, the browser copies the original video track packet by packet next to a new AAC audio track, which carries the translated voice over the original music and effects. Both H.264 and HEVC fit in MP4, so the result is normally an MP4.

Because the picture is copied, the translated file keeps the original codec, resolution and quality. An HEVC phone video stays HEVC after translation, with exactly the same playback compatibility it had before. If your audience cannot play HEVC, convert the translated MP4 to H.264 in a desktop tool before sharing it; how to convert video formats walks through that.

The video picture itself never leaves your device; only compressed audio chunks are uploaded over HTTPS. A dub costs 50 credits per minute with a 2-minute minimum, so a 6-minute training clip costs 300 credits (30¢), whichever codec it uses. If you only need a transcript of an iPhone recording, the MOV to text page covers that case.

Next step

Decide by destination, not by reputation. List where the file will play, check whether every one of those places handles HEVC, and export H.264 if any of them is uncertain. Keep a high-quality master in whichever codec your archive can reliably decode.

Frequently asked questions

Is H.265 better quality than H.264?

At the same bitrate, H.265 usually looks better because it compresses more efficiently. At a generous bitrate, both can look excellent and the difference becomes hard to see. The advantage of H.265 is mainly reaching acceptable quality with smaller files.

Why does my H.265 video not play on some computers?

Playing HEVC smoothly usually needs a hardware decoder or a suitable software decoder, and support differs across operating systems, browsers and older machines. A file that works on a recent phone may fail on an older laptop. The HEVC compatibility guide covers diagnosis and fixes.

Should I record on my phone in high efficiency or most compatible mode?

High efficiency saves storage and is fine if you edit and share on recent devices. Choose most compatible when footage goes straight to people or systems you do not control, because H.264 plays almost everywhere. Converting later is possible but adds a re-encode.

Does converting H.264 to H.265 save space without losing quality?

It can save space, but every re-encode loses some quality, and the saving depends on the settings you choose. Re-encoding at a low bitrate to make a file tiny can visibly degrade it. If the original plays where you need it, keeping it as is avoids the loss.

What about AV1?

AV1 is a newer, royalty-free codec designed for efficient streaming, with support growing in browsers, platforms and recent hardware. Encoding it in software is slow, and older devices may lack hardware decoding. It is another option to weigh by destination, not a replacement for every use.

Will mydubly convert my HEVC video to H.264?

No. mydubly copies the original picture without re-encoding it, so an HEVC source produces an HEVC translated video. If your viewers need H.264, convert the result in a desktop tool such as an editor or ffmpeg after translation.