The Apple Watch Series 4 earns a 6 out of 10 on our repairability scale (10 is the easiest to repair):

Watch band replacements remain fast and simple, and are even backward-compatible with previous models.

Screen replacements are difficult but do-able—it's the first thing to come off, and detaches via simple ZIF connectors.

Battery replacements are pretty straightforward, once you're inside.

While not proprietary, incredibly tiny tri-point screws are a repair hinderance. And they are all over the place.

Several component flex cables are mounted directly to the S4 package, requiring skilled microsoldering to replace.

The resin-encased S4 system makes most board-level repairs impossible.