H.264 and H.265: The Two Dominant Codecs
H.264 (also called AVC, Advanced Video Coding) was finalized in 2003 and became the universal standard for video. Every device, browser, and platform manufactured in the last 15 years supports H.264 hardware decoding. It powers YouTube, Netflix, Blu-ray discs, video calls, and security cameras.
H.265 (also called HEVC, High Efficiency Video Coding) was finalized in 2013 as H.264's successor. It uses more advanced compression techniques — larger coding tree units (up to 64x64 vs H.264's 16x16 macroblocks), better motion prediction, and improved entropy coding — to achieve approximately 40-50% smaller files at equivalent visual quality.
Side-by-Side Comparison
| Aspect | H.264 (AVC) | H.265 (HEVC) |
|---|---|---|
| Standard | ITU-T H.264 / ISO 14496-10 (2003) | ITU-T H.265 / ISO 23008-2 (2013) |
| Compression efficiency | Baseline (1x) | 40-50% smaller at same quality |
| Typical CRF range | 18-23 (visually lossless at 18) | 24-28 (equivalent quality range) |
| Encoding speed | Fast (hardware + software) | 3-10x slower than H.264 |
| Max block size | 16x16 macroblocks | 64x64 coding tree units (CTU) |
| Max resolution | 4096x2304 (4K) | 8192x4320 (8K) |
| 10-bit color | High 10 profile (rare in practice) | Main 10 profile (common, HDR) |
| Browser support | All browsers (universal) | Safari only; Chrome/Firefox partial |
| Mobile HW decode | All smartphones since ~2008 | iPhone 6+ (2014), most Android 2016+ |
| Desktop HW decode | All GPUs since ~2010 | Intel 6th gen+, AMD Polaris+, NVIDIA Maxwell+ |
| Licensing | MPEG LA pool (well-established) | Complex: MPEG LA + Access Advance + independents |
| YouTube upload | Recommended | Accepted (re-encoded anyway) |
Real-World File Size Savings
The headline "50% smaller" is based on academic studies using controlled test content. In practice, the savings depend on the content type and encoding settings. Here are typical results for a 10-minute 1080p video:
| Content Type | H.264 CRF 23 | H.265 CRF 28 | Savings |
|---|---|---|---|
| Talking head (podcast) | ~120 MB | ~55 MB | 54% |
| Screen recording | ~80 MB | ~35 MB | 56% |
| Action movie scene | ~250 MB | ~140 MB | 44% |
| Nature documentary | ~200 MB | ~105 MB | 48% |
| Animation / cartoon | ~70 MB | ~30 MB | 57% |
H.265's advantage is greatest with static or slowly-moving content (talking heads, screen recordings, animation) and smallest with fast-motion, high-detail content (action scenes, sports). On average, expect 40-50% file size reduction at equivalent perceptual quality.
Encoding Speed: The H.265 Penalty
H.265's better compression comes at a significant computational cost. The larger block sizes, more motion prediction modes, and advanced algorithms require much more processing time:
- Software encoding (x265 vs x264): H.265 is typically 3-10x slower than H.264 at equivalent quality presets. A 10-minute video that takes 2 minutes to encode as H.264 might take 10-20 minutes as H.265.
- Hardware encoding (NVENC, QuickSync, VCE): GPU encoders are much faster, but H.265 hardware quality is noticeably worse than software x265 at the same bitrate. The gap is narrowing with newer hardware (NVIDIA Ada Lovelace, Intel Arc).
- Decoding: both codecs decode efficiently on hardware that supports them. H.265 requires slightly more power, which matters for battery life on mobile devices.
Practical tip: if encoding speed matters (live streaming, batch conversion), use H.264. If file size matters and you have time (archiving, storage-limited devices), use H.265. For online conversion tools like ours, H.264 is the standard choice because it balances quality, speed, and universal compatibility.
Device & Browser Compatibility
This is where H.264 has its biggest advantage — it works literally everywhere:
| Platform | H.264 Support | H.265 Support |
|---|---|---|
| Chrome | Full | HW-only (no software fallback) |
| Firefox | Full | HW-only (Windows/macOS) |
| Safari | Full | Full (macOS 10.13+, iOS 11+) |
| Windows 10/11 | Native | Requires HEVC extension ($0.99) |
| macOS | Native | Native (10.13 High Sierra+) |
| iPhone / iPad | Native | Native (iPhone 6+) |
| Android | Native | Most devices 2016+ (varies) |
| Smart TVs | Universal | Most 2016+ models |
| Older devices (pre-2015) | Yes | No |
The key issue: Windows requires a $0.99 HEVC extension from the Microsoft Store for H.265 playback, and Chrome/Firefox only decode H.265 when hardware acceleration is available. If you are sharing video with others and cannot control their devices, H.264 is the only safe choice.
When to Use Each Codec
Use H.264 when:
- You are sharing video with others (email, messaging, cloud links)
- You are uploading to social media (YouTube, Instagram, TikTok)
- You are embedding video on a website
- You need fast encoding (live streaming, batch processing)
- Universal playback is a requirement
Use H.265 when:
- Storage space is limited (phone, external drive, NAS)
- You control the playback devices (all support H.265)
- You are archiving video for long-term storage
- You are working with 4K or 8K content where H.264 file sizes become impractical
- You are recording on an iPhone (default since iOS 11) and staying within the Apple ecosystem
The Future: AV1
AV1, developed by the Alliance for Open Media (Google, Apple, Meta, Netflix, Amazon), is the next-generation codec designed to replace both H.264 and H.265. Key advantages:
- Royalty-free: unlike H.265's complex licensing, AV1 is free for everyone
- 20-30% smaller than H.265 at equivalent quality
- Supported by: YouTube, Netflix, Chrome, Firefox, Android (hardware decode in newest chips)
The main drawback is encoding speed: AV1 is 10-100x slower than H.264 to encode with software. Hardware AV1 encoding (NVIDIA Ada, Intel Arc, AMD RDNA3) is improving rapidly but still not mainstream. For now, H.264 remains the practical choice for most users, with H.265 for space-conscious archiving.