Blender's Auto Keying automatically records keyframes for any transformations made to selected objects. It's a default feature, but leaving it enabled by mistake can lead to butchered animations and lost hours. You're Auto Keying, an addon from Inlet, makes that state obvious across Blender's interface.
The addon adds indicators on the targeted object outliner, the keyframe playhead, the preview viewport, Pose Mode outlines and the preview window header. You can adjust the colors through the addon to suit your eyes, and the Auto Keying button is placed at the furthest right side of the header for extra attention.
A Fetch Color button records your UI theme's default colors so the addon knows what to revert to when Auto Keying is off — you run it once, then again only if you change your Blender theme. A version of the addon without a visible button is also included, which you enable and disable with a hotkey. It supports Blender 2.83 through 5.0.