Why 'Write Once, Run Everywhere' Often Falls Short in Practice

The promise of "write once, run everywhere" has been a lie for thirty years. The desire behind it is real — nobody wants three codebases drifting — but the actual delivery has been: write once, debug everywhere, ship three slightly different apps.

I've watched teams ship a beautiful web product, then spend six months rebuilding it for iOS, then three more months for Android, then quietly accept that notifications behave differently per platform forever. The fragmentation isn't a bug. It's the default outcome of trying to make fundamentally different rendering systems agree on every pixel. The hardest part isn't the rendering itself — it's the long tail of edge cases where the platforms diverge. A button that wraps to two lines on Android but one on iOS.

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This is an excerpt. Read the full post at otf-kit.dev/blog/cross-platform-consistency-myths — full-stack kits your AI coding agent can actually ship to production. Browse the kits →