What Chrome already does

Chrome can reopen the last session if you choose “Continue where you left off”, and Ctrl+Shift+T reopens recently closed tabs. If you’re signed in with sync on, it can also save and sync tab groups. These are worth using. They’re limited, though: the recently-closed list is short, and none of it helps once the session is gone or a profile is reset.

If you already have Plainware Tabs

Open the Plainware Tabs popup after Chrome restarts.
You’ll see a Previous browser session card with the number of tabs and when it ended. The session is sealed at startup, and the new session never overwrites it.
Click Restore missing tabs. Only tabs that aren’t already open are opened.
Windows, order, pinned tabs and tab groups (title, colour and collapsed state) come back. Tabs stay unloaded until you click them, except the active tab in each window, so Chrome doesn’t freeze.
Need something older? Open the vault and restore a whole snapshot, one window, one group or a single tab.

How snapshots work

A snapshot is taken after your tabs, groups or windows change, and every 15 minutes as a safety net.
Before a big loss, such as closing a window with several tabs or a whole group, it keeps the state from just before as a checkpoint.
Automatic snapshots are kept for 30 days for free: all of them for the first 2 days, then thinned to at most two an hour until day 7 and at most two a day after that. Saved sessions and snapshots you star are kept until you delete them.
Everything stays on your computer. Incognito windows are never captured.

The honest limits

It can only restore what it captured. Install it before you need it. It can’t recover a crash that happened earlier.
Some addresses can’t be reopened by an extension, such as certain chrome:// pages. They’re listed in a restore report with a copy button, not dropped silently.
The snapshots live in Chrome’s profile, so a profile reset or uninstall removes them. The free weekly backup file in Downloads is what covers that. See backing up tabs to a file.
Plainware Pro keeps automatic history beyond 30 days (at most two a day) and adds more backup options. Restoring is free.

Other guides

Move your OneTab lists into another tab manager

Export your OneTab lists and import them into Plainware Tabs, which also reads Session Buddy backups and bookmark files. Imports only add, and nothing is skipped silently.

Back up your open tabs to a file

Save all your windows, tab groups and pinned tabs to a file on your computer, by hand or automatically each week. Plainware Tabs backup files work without an account.

Save your tabs and close them, then bring them back later

Park a project: save all your windows as a session, close the tabs to free memory, and restore them later with their groups, a whole window or one tab at a time. No account, free.