Understanding Web HDR Formats
The acronym soup around HDR imaging is confusing. EXR, UltraHDR, Gain Maps, HEIC, AVIF, JPEG-XL... What do they all mean, and why do they break when uploaded to the web? Let's break it down.
1. Apple HEIC
HEIC is the default format used by Apple devices since ~2018. If you take a photo of the sun on your iPhone, it captures the intense brightness using true HDR.
The Problem: Web browsers don't natively render the HDR metadata inside HEIC files properly. If you upload an HEIC photo directly to an HTML <img> tag, it will likely render in standard dynamic range (SDR) and look flat and dull compared to how it looks in the iOS Photos app.
2. Android UltraHDR (Gain Maps)
Introduced in Android 14, UltraHDR is essentially a standard JPEG file with a "Gain Map" hidden inside its metadata.
The Problem: When viewed on an older phone or an incompatible browser, it ignores the gain map and displays a normal, flat JPEG. When viewed on a compatible Chrome browser on an HDR screen, the browser applies the gain map to boost the highlights. However, iOS devices completely ignore Android gain maps.
3. EXR
EXR is the industry standard format used in VFX, 3D rendering, and professional photography. It stores massive amounts of dynamic range data.
The Problem: File sizes are huge, and it cannot be displayed directly in any web browser.
The Solution: AVIF & JPEG-XL
The modern web standard for HDR delivery is shifting towards AVIF and JPEG-XL. These formats support 10-bit color depth and precise transfer characteristics (like PQ or HLG) needed to tell a monitor to "turn up the brightness here".
What HDRJPG does
Our API takes any of the source formats above (HEIC, UltraHDR, EXR) and standardizes them. We generate mathematically correct AVIF, JPEG-XL, and standard JPEGs. When you use our embed snippet, the browser automatically downloads the most efficient true-HDR format it supports, ensuring your users see the photo exactly as the photographer intended.