I was impressed with this clever internal interface at Linear, shown inside this larger blog post:

The dev toolbar exists directly inside the app and allows us to easily toggle feature flags on and off. When something didn’t look right in the refreshed UI, it took us just one click to compare it with the previous version. That made it easier to determine whether the refresh had broken something or whether it had behaved that way before. Having the updates live behind feature flags also meant that instead of developing the redesign in isolation and shipping all the changes at once, we could integrate incremental changes to the platform.

I also cut it out here so it’s easier to see:

Here’s what I like about it:

• It’s a separate UI surface: Rather than being awkwardly integrated alongside production UI and adding jank to it, it is a clearly delineated toolbar you know users won’t ever see, allowing the rest of the interface to always feel like production.
• The feature flag toggling is easy: You don’t have to go anywhere else and possibly log in to toggle a flag, and you don’t have to wait for it to take effect. This will mean more people than just the core team members will be using it.
• Toggling this particular feature flag is as easy as clicking on a tile: I don’t know if anyone can promote others flags their care about to be easily toggle’able tiles, but I can imagine this really beneficial, too.
• The feature flag toggling is instantaneous without any visual jank: I understand that the best way to compare two things visually is to switch between them promptly in situ; our visual system is really good at spotting even small changes when aided this way.

Each one of the above bullet points is individually a small point of friction and easy to renege on, especially when it comes to internal-only interfaces. However, a combination of all of them results in great compounded interest, and I bet makes this interface effective – in addition to just feeling like fun to use.

Appreciate Linear sharing this internal detail; if you are using an interesting internal tool or UI that you are allowed to share, please consider it and let me know!