HEIC vs JPEG: The Technical Differences Explained

Our HEIC vs JPG guide answers the practical question of which format to use. This article goes one level deeper: what is actually different inside the files?

First: JPG and JPEG are the same

JPEG is the name of the standard (from the Joint Photographic Experts Group). .jpg is simply the three-letter file extension that became common because early Windows versions limited extensions to three characters. .jpg, .jpeg and .jpe files are all identical in format.

Compression: DCT vs HEVC

JPEG divides an image into 8×8 pixel blocks, transforms each block with a discrete cosine transform (DCT), throws away high-frequency detail according to the quality setting, and encodes the result with Huffman coding. It's simple and fast, but at lower quality the 8×8 grid becomes visible as blocky artefacts.

HEIC stores images compressed with HEVC (H.265) intra-frame coding — essentially a single video frame. HEVC uses:

• variable block sizes up to 64×64, so smooth areas are coded efficiently while detailed areas get small blocks;
• intra prediction in dozens of directions, predicting each block from its neighbours and coding only the difference;
• more advanced entropy coding (CABAC);
• in-loop filters that reduce blocking and ringing.

The result is that HEIC typically reaches similar visual quality at a considerably smaller file size.

Colour depth and HDR

Baseline JPEG stores 8 bits per channel — 256 levels of red, green and blue. That can produce visible banding in smooth gradients such as skies.

HEIF can store 10-bit or higher colour, with 1,024 levels per channel. That headroom is what makes HDR photos possible. When a 10-bit HEIC is converted to JPEG, it's reduced to 8 bits; for most everyday photos you won't notice, but HDR highlights can't be preserved.

Colour spaces

Both formats can embed an ICC colour profile. iPhones capture in Display P3, a wider gamut than sRGB. A properly converted JPEG keeps the Display P3 profile so colours stay accurate; a careless conversion that drops the profile makes photos look dull. HEIC.IS keeps the profile automatically.

Containers and multiple images

A JPEG file holds one image (plus metadata and sometimes a thumbnail). HEIC is built on the ISO Base Media File Format — the same family as MP4 — so one file can contain:

• a primary image, often stored as a grid of tiles;
• thumbnails;
• auxiliary images such as depth maps and alpha (transparency) channels;
• image sequences and bursts;
• rotation, mirroring and crop instructions applied at display time.

That's why a converter has to understand the container: it must assemble the tiles, apply the rotation and ignore auxiliary images.

Metadata

Both formats carry Exif metadata (camera, exposure, date, GPS) and can carry XMP. In JPEG, Exif lives in an APP1 segment near the start of the file; in HEIC it's a separate item inside the container. One subtle difference: HEIC files apply rotation through a container property, while their Exif may still contain an orientation tag. Converters must reset that tag after rotating the pixels — otherwise the photo appears rotated twice. HEIC.IS handles this for you.

Decoding speed and patents

JPEG decoding is extremely cheap and royalty-free. HEVC decoding is more complex and HEVC is covered by patent pools, which is one reason browser and OS support has lagged. Modern phones and computers include hardware HEVC decoders, which Apple uses to make HEIC practical.

Summary

If you need a HEIC photo to work everywhere, convert it to JPG. If you need maximum fidelity for editing, convert to PNG.