New in the SumatraPDF [pre-release builds](https://www.sumatrapdfreader.org/prerelease):

## Fit by Orientation zoom

New zoom mode **Fit by Orientation** (`CmdZoomFitByOrientation`, View / Zoom menu). It fits width when the window is wider than tall and fits the whole page when it is taller than wide. It updates when you resize the window or rotate the screen ([#702](https://github.com/sumatrapdfreader/sumatrapdf/issues/702)).

![In a wide window at 75% zoom, main menu > Zoom > Fit by Orientation zooms the page to the window width; as the window is resized to taller than wide the whole page fits, back to wide it fits the width again, then tall once more](https://youtu.be/Q3V2FhwLVTo)

## Smooth auto-scroll and Start Auto-Scroll command

Middle-click auto-scroll is now smooth and allows very slow speeds ([#2693](https://github.com/sumatrapdfreader/sumatrapdf/issues/2693)). **Start Auto-Scroll** (`CmdStartAutoScroll`, command palette) starts auto-scroll without a middle mouse button, which helps on laptops: move the cursor away from the starting point to scroll, and run the command again or middle-click to stop.

![Start Auto-Scroll run from the command palette anchors auto-scroll at the mouse: a small move down scrolls very slowly, a larger one faster, moving above the start point scrolls up, and a middle-click stops it](https://youtu.be/rwgWm9N9z9o)

## Expand TOC to Current Page

**Expand TOC to Current Page** (`CmdExpandToCurrentPage`) is in the Bookmarks sidebar's right-click menu and the command palette. It opens the table of contents down to the entry for the current page and selects it ([#1998](https://github.com/sumatrapdfreader/sumatrapdf/issues/1998)).

![Bookmarks sidebar before and after Expand TOC to Current Page: the entry for the current page 5 is expanded and selected](https://files.sumatrapdfreader.org/assets/sumatrapdf/changelog/img/expand-toc-current-page-8b38.png)

## Transparent text selection color

`FixedPageUI.SelectionColor` accepts an alpha value (`#aarrggbb`, e.g. `#40f5fc0c`), so the selection highlight can be more see-through and selected text stays crisp ([#3209](https://github.com/sumatrapdfreader/sumatrapdf/issues/3209)).

![Text selection with SelectionColor = #c01e90ff (mostly opaque) and #301e90ff (more transparent, text stays crisp)](https://files.sumatrapdfreader.org/assets/sumatrapdf/changelog/img/selection-color-alpha-6844.png)

## Localized file type names in Explorer

On non-English Windows, file types associated with SumatraPDF show their translated name in Explorer's "Type" column instead of English names like "PDF File" ([#3323](https://github.com/sumatrapdfreader/sumatrapdf/issues/3323)).

## Better quality when printing large pages

Pages are printed in strips instead of one huge bitmap. This keeps memory use low at any printer resolution, so large pages are no longer printed at reduced quality ([#919](https://github.com/sumatrapdfreader/sumatrapdf/issues/919), [#3510](https://github.com/sumatrapdfreader/sumatrapdf/issues/3510)).

More: [changes from June 17, 2026](https://www.sumatrapdfreader.org/docs/Changelog-2026-06-17) and the [full changelog](https://www.sumatrapdfreader.org/docs/Changelog).