Why Are HEIC Files So Small? Understanding HEIC Compression Technology

The Short Answer

HEIC files are roughly 50% smaller than JPEG because they use a more advanced compression algorithm called HEVC (High-Efficiency Video Coding, also known as H.265). While JPEG uses 30-year-old compression technology that processes images in 8x8 pixel blocks, HEVC uses a much more sophisticated approach with variable-sized blocks (up to 64x64), better motion compensation for image sequences, and improved entropy coding. This modern approach packs the same visual information into significantly fewer bits.

How HEVC Compression Works

HEVC (H.265) is the successor to the H.264/AVC standard and was designed for 4K video compression. When applied to still images in the HEIC format, it uses several advanced techniques: larger coding tree units (CTUs) that can analyze and encode more image area at once, intra-prediction with 35 directional modes (vs JPEG's simple spatial prediction) for more accurate pixel prediction, improved transform coding using multiple transform sizes, and advanced entropy coding (CABAC) for more efficient data packing. These techniques combined allow HEVC to achieve 50% better compression than JPEG at the same perceptual quality.

Real-World File Size Comparison

To illustrate the difference, here are real-world file sizes for the same photo at different settings:

• HEIC (quality 100): ~2.5 MB — maximum quality, minimal compression artifacts
• HEIC (quality 85): ~1.8 MB — excellent quality for most uses
• JPEG (quality 100): ~6.0 MB — virtually no compression, but huge file
• JPEG (quality 92): ~4.0 MB — standard "high quality" setting
• JPEG (quality 80): ~2.0 MB — comparable size to HEIC, but visible artifacts

Does Smaller Size Mean Lower Quality?

Not necessarily. HEIC achieves smaller file sizes through smarter compression, not more aggressive quality reduction. At equivalent file sizes, HEIC produces visibly better quality than JPEG because its algorithm is better at distinguishing between visually important details and redundant information. At equivalent visual quality, HEIC files are about 50% smaller. This means you can store twice as many photos on your iPhone at the same quality level, or keep your existing photos at much higher quality without using more space.

The Trade-Off: Compatibility

The main trade-off for HEIC's excellent compression is compatibility. HEVC/H.265 is patent-encumbered, which means operating system vendors and software developers must pay licensing fees to support it. This is why Windows requires a paid extension to view HEIC files, and why many web services still don't support them. JPEG, by contrast, has been patent-free for decades and is supported everywhere. If you need to share photos outside the Apple ecosystem, converting HEIC to JPEG or WebP is still necessary — but for personal storage, HEIC's compression is unmatched.