Why Don't We Version UIs?
I'm frustrated by the constant UI changes in apps and websites. APIs are versioned, and apps keep old versions around, but UIs never seem to be versioned. I wonder if offering UI versioning could reduce user frustration and allow for better long-term testing.
We've been versioning UIs since 2015, after dealing with a bunch of weird bug reports that we tracked down to people keeping tabs open for months. Needs careful backend planning and backwards compatible data handling, but it's a solvable technical issue. API calls from the front-end can send the active version with calls, letting the backend understand that something older is calling and do version upgrades of envelopes and payloads, and the front-end needs to be designed to ignore extra fields, but all of that is testable, and once things are in place they give you both the protection against weird inconsistency bugs, ability to experiment (running a/b versions in parallel) and detailed monitoring to troubleshoot weird issues. It's quite sobering to look at the list of active versions and see a long tail of what's actually connecting to our backend.
I have seen some older Software/SAAS UIs displaying version numbers. But letting you switch may not make sense because usually a change happens both in backend and frontend and switching versions is not something vendors want to offer due to the complexity of switching required.
When there are big changes, I’ve seen a lot of sites, and even some applications, allow users to opt-in to the new version to try it out, or opt-out of the new version and return to the old one if it isn’t meeting their needs or they have a deadline and need their old workflow to meet it. Reddit and Outlook are the two examples that come to the front of my mind, but I’ve seen many more. Even my power company did it. This however is only for big changes, and usually just a toggle old|new, not fully versioned where a user can go back to any point in history. I would guess that would turn into a nightmare for maintenance, and unlike APIs, there is rarely code that is UI dependent… at least we hope not.
One counter-example is Reddit's old.reddit.com interface, compared to their new one.
For me, avoiding the upgrade treadmill is a reliable way of maintaining stable interfaces (and workflows). Of course that lunch isn’t free. Good luck.
You can if you want, it is a choice, especially if it is a consumer of a versioned API, just like you would version a mobile client.