A sessionstore file with a .jsonlz4 file extension is normally LZ4 compressed, so you can't open it in a text editor for inspection as you would only see binary garbage. Did you decompress the file as in that case you need to use the .json file extension?

You can look at this tool to inspect a compressed jsonlz4 sessionstore file to find a suitable backup to restore. This tool works locally, no uploading done.

• https://www.jeffersonscher.com/res/scrounger.html

Best in such a case is restoring a recent upgrade file created with the most recent update (current is 118.0.2).

You can restore a upgrade.jsonlz4 file from a recent/last update or use a utility to browse Windows System Restore points to see if you can find a recent sessionstore.jsonlz4 file.

A sessionstore file with a .jsonlz4 file extension is normally LZ4 compressed, so you can't open it in a text editor for inspection as you would only see binary garbage. Did you decompress the file as in that case you need to use the .json file extension? You can look at this tool to inspect a compressed jsonlz4 sessionstore file to find a suitable backup to restore. This tool works locally, no uploading done.

• https://www.jeffersonscher.com/res/scrounger.html

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Best in such a case is restoring a recent upgrade file created with the most recent update (current is 118.0.2).

You can restore a upgrade.jsonlz4 file from a recent/last update or use a utility to browse Windows System Restore points to see if you can find a recent sessionstore.jsonlz4 file.

Thanks - that helps! That is the tool I used to recover it, so I believe that what I have is the uncompressed version (which is why I can read it).

In the "step 2" on the Session History Scrounger page, the only options I see to save the file are uncompressed JSON (sessionstore.js format), embedded session (first round only), and uncompressed JSON as text, so I used the uncompressed JSON (sessionstore.js format) option.

Is there a way to convert my js file to jsonlz4? Or another step to use the sessionstore.js file to get my sessions back?

If you still have the compressed .jsonlz4 file you used with the scrounger then easiest is to use that file and rename it to sessionstore.jsonlz4 and place it at the root level of the profile folder with Firefox closed to replace the existing sessionstore.jsonlz4. This is an example of the case where you only use the tool to inspect a compressed file to see whether it is of use and determine what file is best to use for restoring a session.

If you still have the compressed .jsonlz4 file you used with the scrounger then easiest is to use that file and rename it to sessionstore.jsonlz4 and place it at the root level of the profile folder with Firefox closed to replace the existing sessionstore.jsonlz4. This is an example of the case where you only use the tool to inspect a compressed file to see whether it is of use and determine what file is best to use for restoring a session.

Oh, I may be out of luck, then... I do have a file where the file type (not just the extension) shows as JSONLZ4, but I can read it in notepad, so it reads like a typical uncompressed file (not binary gibberish). I must have overwritten the original. Any option to still use that uncompressed file, or does it come down to going through the JSON and manually re-opening the tabs from that one by one?

I think that Firefox would still be able to build the bookmarks from an uncompressed backup since you can create such a backup yourself, you only need to give it the correct file extension (i.e. remove the trailing lz4 to get .json).

You can possibly use this code in the Browser Console to compress or decompress a JSON file.

• https://firefox-source-docs.mozilla.org/devtools-user/browser_console/

javascript:/*(DE)COMPRESS LZ4::2023/10-14*/
(function(){
/*IOUTILS - [80]*/
async function copyFile(inpFile, outFile) {
  var data = await IOUtils.readUTF8(inpFile, /lz4$/.test(inpFile) ? {decompress:true} : {decompress:false});
  await IOUtils.writeUTF8(outFile, data, /lz4$/.test(outFile) ? {compress:true} : {compress:false});
}
var fu = Cu.import("resource://gre/modules/FileUtils.jsm").FileUtils;
var fp = Cc["@mozilla.org/filepicker;1"].createInstance(Ci.nsIFilePicker);
fp.init(window, "Open File", Ci.nsIFilePicker.modeOpen);
fp.appendFilter(".JSON Uncompressed Files","*.json");
fp.appendFilter(".*LZ4* Compressed Files","*.*lz4");
fp.displayDirectory=fu.File(PathUtils.join(PathUtils.profileDir,""));
fp.open((aResult)=>{
if (aResult==Ci.nsIFilePicker.returnOK){
if(fp.file.exists()&&fp.file.isFile()&&fp.file.isReadable()){
var inpFile=fp.file.path;
var outFile=inpFile.replace(/lz4$/i,"")+(/lz4$/.test(inpFile)?"":"lz4");
// prompt(inpFile+"\n"+outFile);
try{
copyFile(inpFile, outFile);
console.log("Saved as: \"file://" + outFile + "\"");
// prompt("Saved as:\n" + outFile,"file://" + outFile);
}
catch(err){console.log(err);}
}
}else{console.log("<canceled>");}
});
})()