# X_ISLAND_INVALID

## Means

an island declaration cannot become a client entry

## Typical cause

no `src`, a remote URL, a file not named `*.island.tsx`, unsafe characters, or two islands on one page claiming the same id. The extension is the rule: a module ships to the browser **iff its name says so**, so the bundler decides without opening the file

## Fix

rename the module to `<name>.island.tsx` and point `src` at it — the cause names the offending value

[Routes, render and budgets](/error-codes#routes-render-and-budgets)