- go to preferences, enable "Show your windows and tabs from last time" option in "When Firefox starts" section
- restart Firefox
- open a few windows (not in private mode), surf a lot of tabs (let's say that it will be session1)
- close Firefox
- start it again (so far it seems good - I'm getting session1 restore correctly)
- open a few windows and tabs again (it will be session2 state of Firefox)
- close Firefox
- run Firefox

- no, it's not a disk issue: there are no any bad blocks nor critical messages from kernel/system about any storage/memory issues
- no, it's not a some extension/addon issue: I've tried to disable all addons - no results
- no, it's not a multi-thread (e10s) feature: I've tried to disable this feature - no results
- looks like it's not a session file issue itself: as I've noticed, "sessionstore.jsonlz4" file is updated during restarts (it's in my Firefox profile directory)
- but maybe it is some Firefox problem during update/restore/compress/decompress "sessionstore.jsonlz4" file itself?

- I can't see "sessionstore.jsonlz4" file when Firefox is running, only when it's closed - is it normal?
- as far as I understand it's a new file format for session (since Firefox 57, as far as I know), but it's not human readable JavaScript, so I can't compare session content between starts: is there any tool to convert sessionstore.jsonlz4 file to sessionstore.js "old format"?
- is there some kind of option in about:config to disable new session file format (maybe it's some lz4 file compression issue on my side?) and to enable session.js old file format
- is there some extension to force save/dump session state "more aggressively" [to file] when Firefox is running?
- is there some way to fix session restore without wiping profile (since I've got a lot of saved history and tons of useful bookmarks)?
- is there some kind of delete sequence for session files in profile directory (including sessionstore-backups directory) to reset "Show your windows and tabs from last time" feature?

Firefox version: 57.0.1 (64-bit) Platform: GNU/Linux Ubuntu 16.04 (with all latest updates) Problem: some tabs/windows are missing between restarts Hello. I'm not sure how to describe it correctly, but looks like I can't get this feature work: I've noticed this issue since upgrade to version 57. Steps to reproduce: - go to preferences, enable "Show your windows and tabs from last time" option in "When Firefox starts" section - restart Firefox - open a few windows (not in private mode), surf a lot of tabs (let's say that it will be session1) - close Firefox - start it again (so far it seems good - I'm getting session1 restore correctly) - open a few windows and tabs again (it will be session2 state of Firefox) - close Firefox - run Firefox What should happen: session2 state. What happens: session1 state. Now, whatever I do, I've got session1 state "basis". However, some of new tabs/windows from the next sessions are restored, but some of them aren't. What I've checked: - no, it's not a disk issue: there are no any bad blocks nor critical messages from kernel/system about any storage/memory issues - no, it's not a some extension/addon issue: I've tried to disable all addons - no results - no, it's not a multi-thread (e10s) feature: I've tried to disable this feature - no results - looks like it's not a session file issue itself: as I've noticed, "sessionstore.jsonlz4" file is updated during restarts (it's in my Firefox profile directory) - but maybe it is some Firefox problem during update/restore/compress/decompress "sessionstore.jsonlz4" file itself? Now I've got a few questions: - I can't see "sessionstore.jsonlz4" file when Firefox is running, only when it's closed - is it normal? - as far as I understand it's a new file format for session (since Firefox 57, as far as I know), but it's not human readable JavaScript, so I can't compare session content between starts: is there any tool to convert sessionstore.jsonlz4 file to sessionstore.js "old format"? - is there some kind of option in about:config to disable new session file format (maybe it's some lz4 file compression issue on my side?) and to enable session.js old file format - is there some extension to force save/dump session state "more aggressively" [to file] when Firefox is running? - is there some way to fix session restore without wiping profile (since I've got a lot of saved history and tons of useful bookmarks)? - is there some kind of delete sequence for session files in profile directory (including sessionstore-backups directory) to reset "Show your windows and tabs from last time" feature? Thanks in advance. And sorry if it is a wrong place for my questions.