Sumatra PDF is a PDF, ePub, MOBI, CHM, XPS, DjVu, CBZ, CBR reader for Windows

Windows update reboots

When I close Sumatra, it remembers all my open tabs and reopens them when I reopen the program. I love that and rely on it. However, when Windows 10 does a reboot due to an update, it closes Sumatra and Sumatra forgets all my open tabs. This is terrible for my workflow as I often leave this open that I mean to come back to later, but forget about. When the reboot happens, they are lost forever. Very frustrating. I know this is already a known issue. I’d just like to know if it’s something that is ever going to be addressed or if it’s something the developer feels doesn’t need changing.

Yes, I plan to fix this. The issue is tracked by

This should now be fixed in latest pre-release version.

Fantastic! I’ll give the pre-release version a try out. Thanks so much.

This is still happening to me on v3.1.2 (64-bit). It is very frustrating. I just lost a huge workspace of open documents.

Is there any way to restore the last session somehow? Where is this information saved?

Naturally, since @kjk clearly said above that he fixed this only in a recent pre-release version.

I’m using the indicated pre-release version, but on my last two reboots, it dumped all my tabs. Very frustrating as I usually have 15+ open at once.

“Naturally”? “…recent pre-release version”? May 14? Oh OK. I didn’t realize almost 6 months ago was “recent”. My bad :ok_hand:

It’s way more “recent” than 3.1.2 in any case which you were using. Posting “This is still happening to me on v3.1.2”, 2 months after kjk said “This should now be fixed in latest pre-release version” hardly made sense…

Nit-picking of “recent” aside, the question is whether the pre-release has fixed the issue for you or you’re still facing the same problem as @sushidog apparently is.

I’m using the pre-release version on both my laptop and desktop, and the recent Windows 10 reboot made me lose all my open tabs on both machines. I love everything else about this software, but this is a big deal as windows 10 reboots so often these days. If anyone has any suggestions for a tabbed reader that survives these reboots, I’d love to hear it.

Windows 10 (including the Home version I believe) allows you to specify a span of up to 18 hours in a day as active hours during which the system will not be restarted to finish installing updates.

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Having used hundreds of apps over dozens of OS systems, I am still experiencing similar problems daily
It is the nature of standard OS ( even some hardened ones) to save work in progress to cached memory and NOT flush to disk (causing slowdown in performance)
depending how windows “crashes” I may OR may not find my changes/preferences captured when re-opening the application or reloading the system (C’est la vie)

It is possible you may find another app that saves users wishes as it runs, but as I have to do daily with apps that cost thousands for a license, you can backup the settings file at the point you have invested much time (before the crash) and replace it if necessary after a crash.
Yes its a work-around rather than improving the application, but I find it essential for not loosing hours of work.

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I just re-tested latest pre-release and after os restart Sumatra did re-open the files correctly.

Unfortunately I can’t debug what happens on other people’s computers.

not wishing to force your hand however I suffer frequent crashes daily since I have to use Win 7 8 and 10 at different points in my work days
I have seen many different behaviours on file states during freeze and shutdown.

one simple way to address this “restore previous session” issue may be to save a settings.bak file at strategic points such as opening a new tab then on starting SumatraPDF offer the user choice (toggle) of resetting to last backup, thus only loosing last entry

I agree this would counter your prime reason (per blog) for making a PDF viewer that is fast to load, however it could be seen as making it more robust.

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@kjk How does the pre-release build save the session? And what could prevent the session from saving/restoring?

Could it be as simple as periodically saving a simple session file containing the required info to restore open docs? And, if maybe there’s a problem restoring, the app could allow manual save/restore of a session. This would be OK with me. I’d rather that, than have to re-open my massive workspace of files.

FYI… for anyone annoyed and frustrated with Windows’ forced reboot, I can suggest one solution. I’ve been using an app called “O&O Shutup10”. Weird name, but it does a great job at disabling MS Windows auto-reboot (as well as many other covert behaviors). Note that you’ll need to manually do Windows Updates if you disable the auto-update/reboot.


Your open file list is periodically updated in your SumatraPDF-settings.txt file
that is the one to back up in case windows shutdown “corrupts” the normal flush or for some other reason “remember open files” is compromised

In a normal installation you will find it at %AppData%\SumatraPDF
you can copy and paste that into the top address bar of windows explorer or create a shortcut, In a “portable installation” it should be in the same folder as SumatraPDF.exe

once your files are “as you like it” then copy that file so you can replace it if it gets trashed by lightning (it honestly happened to me that a highly valuable graphics data file visually exploded before my eyes as a remote server site was struck)

I know about being able to specify when Windows 10 is active. That doesn’t help anything. The program reboots in the middle of the night or when I’m not around.

The pre-release version or Sumatra works sometimes, but it windows crashes it doesn’t recover the tabs. Also, if on a laptop that runs out of power, it doesn’t recover the tabs.

The SumatraPDF-settings.txt file is interesting. My laptop ran out of power, I restarted and all my tabs were forgotten (i.e. Sumatra opened with no tabs open). But looking at the settings txt file, I see references to all the previously open tabs.

Is there any way for me to get Sumatra to read this file and open the tabs?

My SumatraPDF-settings.txt file is located at appdata\roaming\SumatraPDF\


taking one part at a time

it is not the history list of files that were opened e.g.
FilePath = C:\whatever\pdf-sample.pdf
Favorites [
IsPinned = false
IsMissing = true
OpenCount = 0
UseDefaultState = false
DisplayMode = …etc etc
ReparseIdx = 0

it is this later section after Session Data that will be opened IF TABS are active at start

SessionData [
TabStates [
FilePath = D:\2017\Client Invoice 1029.pdf
DisplayMode = continuous
PageNo = 1
Zoom = fit width
Rotation = 0
ScrollPos = -1 -1
ShowToc = false
TocState = 1 3
FilePath = C:\AppData\Banking agreement.pdf
DisplayMode = book view
PageNo = 1
Zoom = fit page
Rotation = 0
ScrollPos = -1 -1
ShowToc = false

you can manually add your own files as required

if the file is valid the tabs will open

NOTE it is easy to corrupt the file manually so keep a backup before editing with notepad
ALSO if the path is invalid because you move files about Sumatra will remove the incorrect entries for the session (although it keeps them in the history list) as “is missing = true” thus their display state can be remembered if restored/reopened

it may be useful to cull any old dead entries in the larger history list

hope that helps