HDR image formats, explained

An HDR photo keeps light that a normal photo loses: a window with the sun behind it, a neon sign at night. On an HDR screen, those parts show brighter than the white of the page around them. iPhone 12 and later, iPad Pro, the 14 and 16-inch MacBook Pro from 2021 on and Apple's XDR displays show full HDR; other recent Macs and iPads show a milder effect, and only at moderate brightness. So do recent flagship Android phones (Pixel 7 and later, Galaxy S24 and later, on Android 14 or later) and monitors with HDR switched on. On any other screen, the same photo appears as a standard image.

The confusing part is the formats. Several file formats can carry the extra light, and no two browsers support the same ones. This page explains each format and where it stands.

The short answer

No single format shows HDR in every browser. To reach almost all of them, publish each photo in several formats at once: a gain map JPEG, an HDR AVIF and a short HDR MP4. Then embed them with markup that lets each browser use the one it can show in HDR, like HDRJPG's recommended embedding. Browsers and screens that cannot show HDR get a normal photo. Keep HEIC, EXR and RAW for shooting and editing, not for publishing.

A gain map JPEG on its own is the safest single file, because every browser can show its standard picture. But on its own it shows HDR only in some browsers, and never in Firefox.

No row says "yes" everywhere. That is why the answer is several files, not one. Two silent cases are worth knowing: Safari 26 shows HDR images only on iOS 26, iPadOS 26 and macOS 26, so Safari 26 on an older macOS shows standard pictures; and Windows shows no HDR at all while its HDR setting is off, which is the default on battery.

Gain map JPEG, Ultra HDR and ISO 21496-1

A gain map JPEG is two images in one file. The first is an ordinary JPEG, which every program and browser can open. The second is the gain map: a small image that says, pixel by pixel, how much brighter each part of the photo should be on a screen that can show it.

A browser that understands gain maps combines the two images. It also adapts the result to how much brightness the screen can give at that moment. A browser that does not understand gain maps shows the ordinary JPEG and ignores the rest. This makes the format a safe fallback: every visitor gets a proper photo. It does not make it enough on its own: Firefox users, anyone on Safari before 26 or on Safari 26 with an older macOS, and anyone on Windows with HDR switched off see only the standard picture. It works best as one of the files, next to AVIF and HDR video.

The same idea goes by several names:

• Adobe's gain map specification, published in February 2023, is where the idea on the web started; Camera Raw was the first app to write it.
• Ultra HDR is Google's version, built on Adobe's metadata and introduced with Android 14 (October 2023). Pixel 7 and later and Samsung Galaxy S24 and later, among others, save their photos this way.
• ISO 21496-1 is the international standard, published in July 2025 and developed with Adobe, Apple and Google. Apple calls its version Adaptive HDR: the iPhone 15 and later shoot photos with it, and iOS 18 and macOS 15 read and write it. Since late 2024, Lightroom Classic and Camera Raw exports with Maximize Compatibility write this form too.

The variants differ in their metadata, not in the idea. Chrome reads the Adobe, Google, Apple and ISO variants; Safari 26 reads the ISO, Adobe and Apple ones. In the HDRJPG API, the gain map JPEG is requested with the format code jpeg-xt. The name is historical: the file is a gain map JPEG in the Ultra HDR layout, not a file in the older JPEG XT standard (ISO/IEC 18477), which no browser reads.

AVIF

AVIF can store a true 10-bit HDR image, using the same transfer functions as HDR video (PQ or HLG). Chrome and Edge show HDR AVIF files, and Safari does too since version 26 on iOS 26 and macOS 26. An AVIF is usually smaller than a JPEG of the same quality, though nobody has published a fair comparison with a gain map JPEG in HDR.

The problem is the fallback. A plain HDR AVIF has no standard version inside it. On a screen that cannot show HDR, the system or the browser has to compress the range into normal brightness, and there is no standard way to do that: Safari, Chrome and browsers without HDR support give different results, and Firefox shows it far too dark. An AVIF can also carry a gain map, which Chrome reads since version 129 and Safari since 26. Either way, AVIF works best as one file of several, next to a gain map JPEG and an HDR video, offered together in a <picture> element. It should not be the only file.

JPEG XL

JPEG XL compresses well and can be HDR. Safari has decoded it since Safari 17 (2023), Chrome since Chrome 155 and Firefox since Firefox 158, both in October 2026; Edge, Opera and Samsung Internet lag behind. Whether Chrome and Firefox show an HDR JPEG XL in HDR is not documented yet, and Safari shows PQ-encoded JPEG XL in HDR but not JPEG XL with a gain map. Most visitors' browsers take months to update, so treat it as an extra, not as the fallback.

HDR video

A photo can also be published as a very short, silent HDR video. Browsers have supported HDR video longer than HDR images: Safari since version 14 (2020), Chrome on Windows with HDR mode on since version 64 (2018), Firefox on macOS since version 100 (2022) and on Windows since version 153 (2026), though not on Linux. HDRJPG's embedding uses an MP4 this way, in the browsers that cannot show the HDR image formats, so their visitors see the photo in HDR too.

HEIC, the iPhone's format

iPhones save photos as HEIC by default. Since 2020 and the iPhone 12 generation, those photos carry a gain map. Safari has displayed HEIC since Safari 17, and shows its HDR since Safari 26 on iOS 26 and macOS 26. Chrome, Edge and Firefox do not display HEIC at all. So a HEIC photo put straight on a page is missing for most visitors. Convert it first, keeping its HDR data, into the set of web formats described above. See how to keep the HDR from an iPhone photo.

EXR and Radiance HDR

EXR (OpenEXR) and Radiance .hdr files store the full range of light as floating point numbers, with no processing. They come out of 3D renderers, exposure bracketing and visual effects work. They are the best source you can have for an HDR photo, and you can make one from any photo in Photoshop or Affinity Photo: see how to create an HDR EXR image. No browser displays them, so they must be converted. HDRJPG accepts EXR directly.

What HDRJPG does with these formats

Any image tool can turn a HEIC into a JPEG. The hard part is keeping the HDR while doing it: reading the light the source file holds, and writing it into every output file in the form each format uses. That is what HDRJPG does. You send one HDR source: an iPhone HEIC, an Android or Lightroom gain map JPEG, or an EXR. You ask for the sizes and formats you need. HDRJPG returns every size you need as a gain map JPEG, an AVIF and a short MP4, and optionally JPEG XL, all of them still HDR.

The other half is showing them. The embedding guide gives the markup that offers all of these files to the browser and makes sure each one uses the file it can show in HDR. This multi-format, multi-file approach is what gets the widest compatibility. Together, the files and the markup mean the same photo displays in full HDR on an iPhone, an Android phone, a Mac or a PC with an HDR monitor, and as a normal photo everywhere else. The examples show the results next to their standard versions.

If your photo has no HDR data at all, HDRJPG can expand its dynamic range to HDR. That is how the NASA Artemis II photos were made. It brightens the light that is already in the file; it cannot bring back highlights the original clipped.