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SageThumbs2K-Portable-2.3.0-arm64.zip 2026-08-20 22.1 MB
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SageThumbs2K-Portable-2.3.0.zip 2026-08-20 23.8 MB
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SageThumbs2K-Setup-2.3.0-arm64.exe 2026-08-20 12.5 MB
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SageThumbs2K-Setup-2.3.0.exe 2026-08-20 13.8 MB
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README.md 2026-08-20 8.4 kB
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SageThumbs 2K 2.3.0 source code.tar.gz 2026-08-20 5.2 MB
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TL;DR

🔁 Changed

  • Large JPEG XL images thumbnail about 70x faster
  • DDS and DXT game textures thumbnail about 5x faster
  • Command line, AI tools and right-click preview match thumbnail quality
  • AVIF thumbnails are dramatically faster across every variant
  • Large AVIF and BMP images thumbnail much faster
  • JPEG photos thumbnail up to 20x faster
  • Every large image thumbnails several times faster
  • HDR images thumbnail about 4x faster
  • Big GIFs thumbnail several times faster
  • WebP thumbnails are about 4x faster with the Windows codec

🩹 Fixed

  • Wide-gamut JPEG photos no longer thumbnail in wrong colours
Read more: everything in 2.3.0 ### Fixed - **Wide-gamut JPEG photos could thumbnail in the wrong colours.** A photo saved in AdobeRGB or Display P3 carries a colour profile describing how its numbers should be read. On the faster decoding path Windows does not hand that profile over, so the numbers were used as-is and the thumbnail came out visibly off - most likely on camera photos, which are exactly the files that tend to be wide-gamut. SageThumbs now reads the profile out of the file itself. Every other viewer already showed these correctly, so only the thumbnail was wrong. ### Improved - **Large JPEG XL images thumbnail about 70x faster.** A 12-megapixel .jxl took over a second and a half; it now takes about a fortieth of that. JPEG XL stores a small version of the picture inside the file, ahead of all the fine detail, and the decoder was building the whole full-size image anyway before shrinking it down. It now stops at the small one when a thumbnail is all that was asked for. Nothing about the picture changes that you could see - it matches a full decode to within about four levels out of 255 - and small images, or ones where the small version would be too coarse, still decode in full. Lossless .jxl files are unaffected, as they do not carry that small version. - **DDS / DXT game textures thumbnail about 5x faster.** A large compressed texture used to be unpacked in full, pixel by pixel, just to work out the average colour of each little block. Two changes removed that work: the thumbnail is now built a block at a time instead of assembling the whole surface first, and each block's average is worked out directly from the block's own endpoints rather than by expanding its sixteen texels. Together they take a 12-megapixel texture from about 180 ms to about 33 ms. The picture is not merely similar but identical, which is checked automatically against the old method on tens of thousands of blocks. - **The command line tool, the AI tools and the right-click preview now produce the same quality picture as Explorer's thumbnails.** They had been using a cheaper, slightly softer way of shrinking images than the thumbnails themselves. They all share the better one now, so a preview looks the same wherever you see it. Image sizes are unchanged. - **AVIF thumbnails are dramatically faster - now across every common variant.** A user told us (fairly) that our AVIF was much slower than Windows' own thumbnails. Two causes, both fixed. First, the AVIF path was rendering a full-size image and then shrinking it, throwing nearly all the work away; it now renders straight to the size the thumbnail needs. Second, 10- and 12-bit AVIF (most HDR and camera output) was taking an expensive detour to keep its colours correct; the colour error it was avoiding turns out to be exactly reversible, so those files now decode on the fast path and get corrected in place. The net effect on a 6-megapixel 10-bit AVIF: about fifty times faster than 2.2.0, with slightly MORE accurate colour. The last slow case fell too: 8-bit AVIF carrying the colour signalling that `avifenc` and `ffmpeg` write by default (which Windows' own decoder pipeline misreads, and which we therefore used to hand to a slower external decoder to keep colours right). Those files now decode through Windows' AV1 decoder directly while SageThumbs applies the correct colour conversion itself: same accurate colour, roughly 10-40x faster depending on size. Only an AVIF with no colour information at all still takes the careful slow path. - **Large images thumbnail much faster.** Two formats were doing far more work than the picture needed: a 12-megapixel AVIF took about 180 ms and a 12-megapixel BMP about 259 ms, against Windows' own 65 ms and 22 ms. Both now do only the work the thumbnail size actually requires - **AVIF is down to ~39 ms and BMP to ~20 ms**, which makes both faster than or equal to Windows. Colours are unchanged. - **JPEG photos thumbnail up to 20x faster.** SageThumbs can ask the JPEG decoder for a small version directly instead of decoding every pixel and shrinking afterwards, but it was only doing that for files over 512 KB. A JPEG's size depends on its quality, not its megapixels, so a 6-megapixel photo saved at ordinary quality missed out while a smaller one at high quality did not. That limit is gone: a typical photo now goes from about 75 ms to about 5 ms, and the thumbnails come out identical. - **Every large image thumbnails several times faster, in any format.** Shrinking a big picture down to a 256-pixel tile was costing more than decoding it in the first place - about 800 ms for a 12-megapixel image. It now does the bulk of the shrinking in one cheap pass and leaves only the last step to the high-quality filter, which is about **5x to 16x faster** with no visible difference (measured at under one part in 255 on deliberately difficult content). - **HDR images (.hdr) thumbnail about 4x faster.** A high-dynamic-range photo was having its brightness curve applied to all twelve million pixels before anything was shrunk down to a thumbnail. It now shrinks first, which is both quicker (about 600 ms to about 160 ms) and slightly more accurate, since averaging brightness before compressing it is the correct order. OpenEXR files have always worked this way; .hdr now matches them. - **Big GIFs thumbnail several times faster.** A large GIF was decoded at full size and then shrunk, doing the full amount of work for a picture nobody ever sees at that size. A 12-megapixel GIF took about 306 ms against Windows' 50 ms; it now takes about 47 ms, which is fractionally faster than Windows. Animated GIFs are untouched, so which frame you see never changes. - **WebP thumbnails are ~4x faster when the Windows WebP codec is installed** (it ships with Windows 11). Still images now use the system codec, which is much quicker than our built-in decoder; animated WebP and machines without the codec keep the previous behaviour, so nothing is lost either way.

Verified installer

  • File: SageThumbs2K-Setup-2.3.0.exe
  • Size: 13791330 bytes

  • SHA-256: 2c95e8e693ebaf5d2d652126d81919b94e3726883785b8b398f2684f2fa97bcf

  • ARM64 installer: SageThumbs2K-Setup-2.3.0-arm64.exe

  • ARM64 SHA-256: fb1c23928f0f53a8751c74ccff897fc0dfa8c116594ce02e71deeb43d971f37c

Portable (no installer)

Extract and run. Nothing is installed, nothing goes in the registry, no admin needed. Settings live in SageThumbs2K.ini next to the exe.

You get the app and the command line tool: settings, convert and resize, quick preview, screenshots, OCR, the colour picker and the folder tools.

Explorer thumbnails and the classic right-click menu work too. Turn them on with st2k register, or the button in Settings under Advanced. That registers the handler for your user account only: no installer, no administrator rights, nothing written machine-wide. st2k register --off undoes it, and you should run that before moving or deleting the folder, otherwise Windows is left pointing at a file that has gone.

Three things still need the installer, because Windows only accepts them registered for the whole machine: the Explorer preview pane, the Details pane columns, and the Windows 11 right-click menu (the compact one).

  • x64 portable: SageThumbs2K-Portable-2.3.0.zip

  • x64 portable SHA-256: 92c26b1a4bf0e21b630430d7f884d1b6f5a859b9d4ecfecd64199ce00d3f779a

  • arm64 portable: SageThumbs2K-Portable-2.3.0-arm64.zip

  • arm64 portable SHA-256: 3891f59e65da28f268411c46dc2ead250f6c894afdb99e1c663e659cb7ea1938
Source: README.md, updated 2026-08-20