Formats and codecs

First, what this page does not affect:

Finding duplicates never depends on a decoder

Exact duplicate detection reads bytes. It works on every file on your disk — formats DuoBolt has never heard of, encrypted archives, disk images, files with no extension at all. Nothing on this page limits it.

Decoding matters only for two things: previews, and matching photos by what they look like.

Images

Decoded on both macOS and Windows:

Format	Extensions
JPEG	jpg, jpeg
PNG	png
TIFF	tif, tiff
WebP	webp
BMP	bmp
GIF	gif (first frame)

JPEG runs on a dedicated fast path that decodes at a reduced scale.

HEIC, HEIF and AVIF

macOS decodes all three through the system image stack. Nothing to install.

Windows decodes all three too, through WIC — but that requires two Microsoft Store packages, both free:

HEIF Image Extensions

Microsoft.HEIFImageExtension — for HEIC and HEIF, which is what an iPhone produces by default.

Get it from the Microsoft Store

AV1 Video Extension

Microsoft.AV1VideoExtension — AVIF images are AV1 frames, so this is the one they need.

Get it from the Microsoft Store

Without them, Windows reports the codec as missing and the tile falls back to a placeholder. The files are still found, hashed, grouped and removable — only the thumbnail is missing.

RAW

If you shoot RAW + JPEG, the pair is one photograph in two files — see RAW + JPEG duplicates for how a group of those is settled.

DuoBolt reads the embedded preview that cameras write inside RAW files rather than demosaicing the sensor data, which is both far faster and closer to what the camera showed you.

Maker	Extensions
Canon	cr2, cr3
Nikon	nef, nrw
Sony	arw
Adobe	dng
Fujifilm	raf
Panasonic / Leica	rw2, rwl, raw
Olympus	orf
Pentax	pef
Samsung	srw
Sigma	x3f

RAW without an embedded preview

A RAW file that carries no preview cannot be decoded on Windows, and the scan reports it as skipped. On macOS the system falls back to demosaicing the sensor data directly, so those files still work — the Leica case is the usual one.

In a Photos library scan a JPEG + RAW pair is one photo, as it is to Photos: the tile says JPEG + RAW, the preview switches between the two, and removing the photo removes both.

Video

Previews play through the operating system: AVFoundation on macOS, Media Foundation on Windows. What plays is therefore whatever your machine can already play, and it differs between the two.

Video files are found and matched as duplicates regardless — that is a byte-level question, and it does not involve a codec.

Everything else

Anything outside the tables above is reported as an unsupported format for preview purposes and counted in the scan’s skipped breakdown. It is still part of duplicate detection.

Where decoding matters

How grouping works — photos are matched on what they look like, so a photo DuoBolt cannot decode cannot be grouped.

Where it does not

How duplicate matching works — bytes, hashes, and nothing else.