Firefox creates various session history files as you browse, and then at shutdown creates sessionstore.jsonlz4. In Firefox 56+, the files are compressed using Mozilla's flavor of LZ4 compression (.jsonlz4 or .baklz4 file extension). The JSON data contains rich detail about your session, but this page is targeted toward extracting just the page URLs.
Import Jsonlz4 Bookmarks Into Firefox
Home: Browse: Compressed Files Compressed Files. Compressed files use file compression in order to save disk space. Compressed archive formats can also be used to compress multiple files into a single archive. .jsonlz4 Mozilla bookmarks.jsp JSP script.kdb KeePassX.kdbx KeePassX.key Synology AES key.kmz Zipped Keyhole Markup Language (KML) used by Google Earth.ldf Microsoft SQL Server Log Data File.ldif LDAP Data Interchange Format.lit Microsoft ITOL/ITLS.lnk Microsoft Windows Link (shortcut).lso Logic Platinum File.luks LUKS encrypted file.lwo 3d model.
Jsonlz4 Open
Step 1: Load File
Drag and drop one session history file onto the empty text box (), or use the Browse... button on the right. This file is not sent to the network, it is only read within this page in Firefox.
Note: To scrounge a different file, reload this page (Windows: Ctrl+r. Mac: Command+r). Or click the reload button in the address bar.
Step 2: Extract URLs / Save Session Links
HTML list options:
HTML list commands: (Fallback: )
JSON file:
Extracted using https://www.jeffersonscher.com/ffu/scrounger.html
My Firefox (Quantum v.66 on Windows 10) crashed, and I accidentally clicked 'Start New Session' instead of 'Restore Session', which lost all of my previous tabs.
Good news: In my profile, in 'sessionstore-backups' folder, I found a large file called previous.jsonlz4, which SEEMS like it contains all of my previous tabs and windows.
I confirmed that it's a valid file using Session History Scrounger for Firefox tool that seemed to be the only useful resource my Googling turned up on the topic.
Bad news: After a couple of days of Googling, I can't seem to figure out how to restore the data from jsonlz4 file to my browser's tabs (basically, turn it back into crash session restore).
What I tried:
Jsonlz4 File
Copied that jsonlz4 into 'sessionrestore-backups' directory as 'recovery.jsonlz4' – which seems to be the file that gets updated when FF crashes as per my experiments. This had no effect.
Copied the JS file that Scrounger created for me into previous.js and recovery.js. No effect.
Deleted 'store.json.mozlz4' file in 'crashes' subdirectory in my profile. No effect.
Jsonlz4 File Type
Notes:
Note: I am NOT looking for random ways to get a list of URLs from the JS file that Scrounger created. I know how to do that. I want to actually import my crashed session into crash session recovery in FireFox, or into active Firefox session.
Note: I'm aware of this similar question but it asks about pre-version-57 session format circa 2012, which seems to have nothing to do with modern post-version-57 session mechanism.