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.
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.
Or open using:
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