Adobe DNG MIME Type
image/x-adobe-dng identifies, how Digital Negative files are structured, which applications open them, and how Poly handles them. MIME type details for image/x-adobe-dng
In active use| MIME type | image/x-adobe-dng |
|---|---|
| Extensions | .dng |
| First standardized | 2004 |
| Created by | Adobe Systems |
| Browser support | |
| Example applications | Adobe Lightroom Classic, Adobe Photoshop, Adobe DNG Converter |
| Poly support | Yes. Poly recognizes `.dng` files, creates thumbnails, and reads available EXIF metadata. It does not provide raw-development controls. |
| Indexed by Poly | Yes. DNG files are searchable by filename, available metadata, and visual similarity. Text visible in the image is not OCR'd. |
| Preview in Poly | Yes. Poly's image viewer shows a rendered preview of the photograph, not an editable development of the raw image data. |
| Poly agent | Yes. The Poly agent can reason about the visible content of the rendered preview, but it cannot inspect the underlying raw samples or every embedded tag. |
What is image/x-adobe-dng?
image/x-adobe-dng identifies an Adobe Digital Negative file, normally stored with the .dng extension. DNG is a documented container for camera raw image data, capture metadata, color-calibration information, and optional rendered previews. It can hold mosaiced sensor samples, or it can hold linear image data that has already been demosaiced.1
The MIME name is conventional rather than registered. Neither image/x-adobe-dng nor the sometimes-used image/dng appears in IANA's current image media-type registry.2 The freedesktop shared MIME database maps .dng to image/x-adobe-dng and treats it as a subtype of both camera raw and TIFF.3 Some preservation tools instead identify DNG as image/tiff, so software should not rely on one Content-Type value alone.
x- prefix does not mean that DNG is undocumented. Adobe publishes the full specification, and ISO published DNG as ISO 12234-4:2026. The MIME label and the file-format standard have separate registration histories.14How to identify a .dng file
DNG extends TIFF 6.0 and follows TIFF's image-file-directory structure.1 A file therefore begins with one of the ordinary TIFF headers:
49 49 2A 00 little-endian TIFF
4D 4D 00 2A big-endian TIFF
Those four bytes are not a unique DNG magic number. An ordinary TIFF and several camera-specific raw formats can begin the same way. A DNG-aware parser also looks for the DNGVersion tag, validates directory offsets and field lengths, and interprets DNG-specific tags. The Library of Congress records signatures that combine the TIFF header with DNGVersion, while also listing the broader TIFF headers.5
A DNG may include several representations of one capture:
- Raw or linear image data used for development.
- EXIF, XMP, IPTC, camera-profile, and private metadata.
- A reduced or full-size JPEG preview for software that cannot process the raw samples.
- In some converted files, the complete original camera raw file as an embedded payload.16
Renaming a TIFF, JPEG, NEF, or CR2 file to .dng does not create those required tags or turn it into a valid Digital Negative.
From Adobe specification to ISO standard
Adobe published DNG 1.0.0.0 in September 2004 and made the specification available for other hardware and software vendors to implement.7 The format was intended to give camera makers and photographers a documented alternative to model-specific raw containers. Adobe's current public specification is DNG 1.7.1.0, dated September 2023.7
In March 2026, ISO published the first edition of ISO 12234-4, Digital imaging, Image storage, Part 4: Digital negative format. The standard specifies the DNG image file format and is maintained through ISO/TC 42.4 This formal standardization is newer than the format itself, so a 2004 DNG and an ISO-era DNG belong to the same evolving family but may require different decoder features.
DNG versions carry both a DNGVersion and a DNGBackwardVersion. The latter tells a reader the oldest specification level needed to interpret the main image correctly.1 An older application can still reject a valid newer file, especially when the file uses a newer compression method or feature.
How to open a DNG file
Use a raw processor when you want access to the editable image data:
- Adobe Camera Raw, Photoshop, and Lightroom read and write DNG as part of Adobe's raw workflow.7
- Adobe DNG Converter converts supported camera-specific raw files to DNG and lets you select a backward-compatibility target.8
- Apple system photo apps have basic DNG support on current Apple operating systems. Apple notes that support for other camera raw formats is camera-specific.9
Chrome, Edge, Firefox, Opera, and Safari do not natively develop DNG as a normal web image. MDN's browser image-format guide does not list DNG among commonly supported web formats.10 For a website, publish a rendered JPEG, WebP, AVIF, or PNG, and offer the .dng separately when visitors need the original.
Support in Poly
Poly recognizes .dng files and gives them the same convenient browsing experience as other supported camera raw formats. It creates sharp thumbnails, opens the photograph in the image viewer, reads available EXIF metadata, and makes the visual content available for similarity and color-oriented search.
The Poly agent can reason about the visible photograph from its rendered preview. Poly does not provide raw-development controls, expose the sensor samples, or OCR words visible inside an ordinary image. A dedicated raw editor is still the right tool for precise white balance, demosaicing, camera profiles, highlight recovery, and complete metadata inspection.
Converting DNG for sharing or editing
Exporting a DNG to a common image format develops the raw data into display pixels. The right destination depends on what must survive:
| Destination | Best for | Important tradeoff |
|---|---|---|
| JPEG | Email, galleries, and broad compatibility | Lossy and usually 8-bit; raw editing latitude is gone |
| TIFF | High-quality interchange and continued editing | Large; stores one rendered interpretation |
| PNG | Lossless exchange of rendered pixels | Large for photographs and no longer raw |
| Another DNG compatibility level | Older raw software | May restrict newer features or change compression |
Adobe's converter can preserve mosaiced data, create a linear demosaiced DNG, leave image data uncompressed, or target an older DNG compatibility level. Mosaic data can be converted to linear data, but that transformation cannot be reversed.8
When converting a proprietary raw file to DNG, Adobe warns that its converter may omit some proprietary metadata. Embedding the complete original raw file avoids losing that original payload, but it increases file size.8 For an important archive, keep the untouched source until you have verified the converted DNG in every application your workflow depends on.
DNG, TIFF, Apple ProRAW, and CinemaDNG
These names overlap, but they are not interchangeable:
| Name | Relationship to DNG | Practical distinction |
|---|---|---|
| TIFF | DNG extends its directory-based structure | A generic TIFF lacks the required DNG tags and raw-processing model |
| Apple ProRAW | Stored in a standardized, linearized DNG container | Carries Apple's computational-photography result and metadata11 |
| CinemaDNG | Uses DNG-oriented image data for cinema frame sequences | A video workflow rather than one ordinary still-photo DNG |
A DNG is not necessarily untouched sensor data. Linear DNG and Apple ProRAW can contain already-demosaiced pixels, while converted DNG files can also carry an embedded original raw file. Inspect the tags and provenance when that distinction matters.
Metadata and privacy
DNG can consolidate EXIF, XMP edits, camera profiles, GPS data, maker notes, previews, and even an original raw file inside one container.18 Removing a visible GPS field from one metadata view does not prove that location or device information is absent from every IFD, preview, private block, or embedded source.
For public delivery, a fresh rendered export with explicitly controlled metadata is easier to audit than the original DNG. Keep the master private when it contains sensitive capture or authorship information.
Footnotes
- Adobe. Digital Negative (DNG) Specification, Version 1.7.1.0. Defines the TIFF-based structure, DNG tags, image-data models, metadata, previews, and version fields. ↩ ↩2 ↩3 ↩4 ↩5 ↩6
- Internet Assigned Numbers Authority. Media Types Registry. The image registry contains no
image/x-adobe-dngorimage/dngentry. ↩ - Debian Sources. freedesktop.org shared MIME database. Defines
image/x-adobe-dng, its.dngglob, and its camera-raw and TIFF relationships. ↩ - International Organization for Standardization. ISO 12234-4:2026, Digital negative format. Records the March 2026 publication and ISO/TC 42 responsibility. ↩ ↩2
- Library of Congress. Adobe Digital Negative (DNG), Version 1.6. Describes DNG identification, TIFF signatures, DNGVersion-based signatures, and format relationships. ↩
- Adobe. Open, Process, and Save Images in Adobe Camera Raw. Documents JPEG previews and embedding the original raw file. ↩
- Adobe. Digital Negative (DNG), Adobe DNG Converter. Publishes the current specification, names supported Adobe applications, and records the September 2004 version 1.0.0.0 example. ↩ ↩2 ↩3
- Adobe. Adobe Digital Negative Converter. Documents compatibility targets, mosaic and linear modes, compression, proprietary-metadata limitations, and original-raw embedding. ↩ ↩2 ↩3 ↩4
- Apple Support. Digital Camera RAW Formats Supported by Apple Operating Systems. States that current Apple operating systems include basic support for DNG files. ↩
- MDN Web Docs. Image File Type and Format Guide. ↩
- Apple Developer. Capture and Process ProRAW Images. Explains that ProRAW uses a standard linearized DNG container. ↩