Just as there is a ticking bomb built into cut/⌘X – if you cut something, and then cut something else again without a paste in between, you overwrite the clipboard without any way to bring it back – there is another one that awaits you when you use undo/⌘Z.

Here’s a typical undo chain, illustrated using Photoshop’s classic interface. You can do things, then undo into the past with ⌘Z to your heart’s content, then zipline back to the present via redo’s ⌘⇧Z:

But if you go far into the undo history and do something then – accidentally or intentionally – poof! Your entire undo stack, no matter how precious and storied it was, evaporates in an instant:

And it’s not even Back to the Future II rules where you can at least go back to the original separation moment and still get the better future for free…

…no, the entire original undo stack is gone.

The most popular solution for the cut problem, inasmuch as it really needs one, is a clipboard manager. Clipboard managers only move forward in time and record everything passing through the clipboard, so even if you override it with a careless cut or copy, you can ask the clipboard manager to resurrect the contents.

The most popular solution for the undo problem is something conceptually very similar – version history. It also always marches forward. Do something new? You’ll see a new version history entry. Undo it? New version history entry. Redo? New version history entry. Both the clipboard manager and version history are like paper ledgers, hostile to erasers and shredders, addicted to additivity.

(Mixing both universes, Figma’s version history will allow you to copy something from its past entry. But, naturally, you won’t be able to cut from it.)

I like this conceptual distinction, and you can see it in places outside of undo, too. Any browser has a tactical back/​forward button staring you in the face, and a strategic history log hiding deeper inside. Linux offers up/​down arrow keys for tactical recall, and history for the ledger:

It all feels like the correct proportionality – the simple thing comes with a quick UI, the heavier thing with an interface that matches its heaviness. This is why I got a bit nervous hearing about persistent undo, because undo is meant to be more like a fruit fly, like stockpiling things on your undersized cafeteria tray, knowing the journey to the table won’t last very long. Undo’s interface is not compatible with longevity.

But even for version history, the devil’s in the execution. Many tools don’t offer version history, and others add to it only at seemingly random intervals. Chrome’s back/​forward buttons are wonderful, but its history UI is a hot mess: slow, and with only an infinite scroll when it comes to exploration. Figma’s version history doesn’t make it as clear as it could (sorry, my bad, I never got around to fixing it) that restoring an older entry is not rewinding back to it like undo, but using ledger rules – so it might not feel as safe in use:

But I also wanted to go back to Photoshop and show you something interesting. One of the history settings offers “non-linear history”:

Turn it on, and a fascinating thing happens: There is no poof. Undo behaves more like a ledger, always marching forward:

It is an interesting idea. In practice, it’s confusing – time is not meant to work this way. But I feel this was really close to a nice solution that could be enabled for everyone: preserve the discarded branch, but keep it off of ⌘Z and only show it in the visual UI so you can get back to it this way, perhaps presenting it slightly off the main axis, perhaps, I don’t know, looking something like this:

Okay, technically the future collapse is *exactly* like Back To The Future II, but given you’re the only actor in the universe, you still have to recreate the future all by yourself. See, now I’m starting to sound like Primer.