Installation

SumatraPDF is distributed in several forms. Pick the one that matches how you want to deploy it.

Download flavors #

Flavor	What you get	Best for
Installer (`SumatraPDF-<ver>-install.exe`)	Installs to `%LOCALAPPDATA%\SumatraPDF` (or `%PROGRAMFILES%` with `-all-users`), registers file associations, optional preview handler	Most users
Portable (`SumatraPDF-<ver>.exe` downloaded as `SumatraPDF-<ver>.zip`)	Single self-contained `.exe` — no separate `libsumatrapdf.dll`, settings live next to the exe	USB stick, custom folder, no installer
Extract only (`-x`)	Unpack files without installing	IT scripts, inspection

Download from sumatrapdfreader.org or pre-release.

Running the installer #

Double-click the installer, or silently:

SumatraPDF-<ver>-install.exe -install -silent

Common options — full list in Installer cmd-line arguments:

Option	Meaning
`-d <dir>`	Install directory
`-all-users`	Install to `%PROGRAMFILES%\SumatraPDF` for all users (ver 3.4+)
`-with-preview`	Register PDF preview in File Explorer
`-with-filter`	Register Windows Search PDF filter
`-log`	Write log to `%LOCALAPPDATA%\sumatra-install-log.txt`

Extract without installing #

SumatraPDF-64-install.exe -x -d "C:\Temp\Sumatra"

Extracts SumatraPDF.exe, libsumatrapdf.dll, sumatrapdf-tool.exe, etc. into the target directory. Does not register file associations. Recent builds do not create Start Menu / desktop shortcuts when extracting only.

Portable vs installed settings #

	Portable	Installed
Settings file	Same folder as `.exe`	`%LOCALAPPDATA%\SumatraPDF\SumatraPDF-settings.txt`
Thumbnail cache	`sumatrapdfcache` next to exe	`%LOCALAPPDATA%\SumatraPDF\sumatrapdfcache`

Override with -appdata <directory> — see Command-line arguments and How we store settings.

Custom settings directory (enterprise / RDP) #

Launch shortcuts with:

SumatraPDF.exe -appdata "D:\Shared\SumatraSettings"

All users sharing that path use the same SumatraPDF-settings.txt. Ensure the directory is writable by every account that runs SumatraPDF.

Upgrade fails: file in use (PdfFilter.dll / PdfPreview.dll / libsumatrapdf.dll) #

Through 3.6 the engine DLL was named libmupdf.dll; from 3.7 it is libsumatrapdf.dll.

When upgrading, the installer renames existing DLLs aside before writing new ones. That can fail if Windows still has the old file open:

File	Often locked by
PdfFilter.dll	Windows Search (`SearchIndexer.exe`, `SearchFilterHost.exe`) after PDF IFilter registration
PdfPreview.dll	File Explorer preview pane / `dllhost.exe` / `prevhost.exe`
libsumatrapdf.dll	Running SumatraPDF, Explorer preview, or Search filter hosts

Typical Windows errors during install: 32 (sharing violation / file in use), 5 (access denied on replace/delete).

What the installer does #

Unregisters the search filter and preview handler (if installed)
Stops the Windows Search service (WSearch) when possible
Kills processes that still load install-dir modules
Renames PdfFilter.dll, PdfPreview.dll, and libsumatrapdf.dll to *.copy
If a rename stays blocked, shows a dialog and retries every few seconds until success or you abort

What you can do #

Close all SumatraPDF windows and other PDF apps
Close Explorer windows that show a PDF preview pane (or turn off the preview pane)
Temporarily stop Windows Search:
- Win+R → services.msc → Windows Search → Stop
- Or elevated: net stop WSearch
Run the installer again (as admin for “all users” under Program Files)
After install, start Windows Search again if you stopped it (net start WSearch)

If the install still fails, reboot and run the installer before opening PDFs or browsing folders with preview enabled.

Corrupted or incomplete installation #

If SumatraPDF reports a corrupted installation:

libsumatrapdf.dll is missing next to SumatraPDF.exe, or
libsumatrapdf.dll version does not match SumatraPDF.exe

Fix: run the official installer, use the portable exe, or extract with -x so both files match.

Also see Failed to load libsumatrapdf.dll if the app starts but cannot load the DLL (often antivirus).

Installer runs when I open a PDF #

SumatraPDF only shows the installer UI when the executable name contains -install (official installers rename themselves that way) or you pass -install. If double-clicking a PDF launches an installer:

File association may point at the installer .exe instead of installed SumatraPDF.exe
You may be running a copied installer from Downloads instead of the installed copy

Re-run the official installer, then check Set as default PDF viewer.

Multiple copies / old versions #

An older SumatraPDF in %LOCALAPPDATA% or a renamed portable copy can confuse file associations. Uninstall via Settings → Apps, then install fresh.

Admin vs normal user #

Do not run SumatraPDF as administrator for everyday reading. An elevated instance cannot open files dropped from a normal Explorer session (“running as admin and cannot open files from a non-admin process”).

Set as default viewer #

After installing, follow Set as default PDF viewer. The portable exe alone does not register defaults.

Command-line tools #

After a full install, sumatrapdf-tool.exe is next to SumatraPDF.exe and on PATH. With the portable EXE you can run the same commands as SumatraPDF.exe <tool> (see Tools), or extract sumatrapdf-tool.exe with -x. No install required.