Dead Code Detector

Systematic process for locating and safely removing code that is no longer used. Always run pre-flight-thinking first — dead code removal can have surprising dependencies.

Detection Techniques

1. Unused TypeScript Exports

Enable strict checks in tsconfig.json if not already set:

"noUnusedLocals": true,
"noUnusedParameters": true

Then run:

pnpm tsc --noEmit 2>&1 | grep "is declared but"

2. Orphaned Files (Never Imported)

# Find .ts/.tsx files that are never imported by any other file
# Start with files that have no import references at all
grep -rL "from.*<filename-without-ext>" --include="*.ts" --include="*.tsx" src/

For a more thorough scan, use ts-prune or knip:

pnpm dlx knip --include files,exports,types

3. Unreachable Code Branches

Look for:

• if (false) or if (0) blocks
• Code after unconditional return, throw, or continue
• Switch cases that can never be reached given the union type

TypeScript surfaces some of these with "allowUnreachableCode": false in tsconfig.

4. Stale Feature Flags

Search for feature flag constants that are hardcoded to a final value:

grep -rn "FEATURE_FLAG\|featureFlag\|FF_\|isEnabled" --include="*.ts" --include="*.tsx"

If a flag is always true or always false, the conditional is dead.

5. Unused CSS / Tailwind Classes

For Tailwind: run pnpm dlx tailwind-rg or inspect the PurgeCSS output of the Vite build.

Safe Removal Process

1. Verify nothing imports the symbol — grep across all packages including artifacts/.
2. Remove the export (not the whole file yet).
3. Run pnpm tsc --noEmit — a type error at a call site means it was used.
4. If zero errors, remove the file or function body.
5. Run pnpm lint to catch any residual references in config or test files.
6. Commit as refactor(<scope>): remove unused <description> for clean history.

What NOT to Remove

• Symbols with @public or @api JSDoc tags — they may be used externally.
• Re-exports from a package's index.ts — they are part of the public API.
• Anything referenced by a string (e.g., dynamic imports, require(variableName)).
• Code guarded by process.env.NODE_ENV — it may be active in a different environment.