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Dead Code Detection Guide
Purpose: Use this file before deleting code that might be unused, exported, dynamic, or protected by feature flags.
Contents
Comprehensive guide for detecting and safely removing dead code across languages.
Detection Tools by Language
TypeScript/JavaScript
| Tool |
Detects |
Command |
Notes |
knip |
Unused files, exports, deps, types |
npx knip |
Recommended — ~300K weekly downloads; auto-detects tooling; VSCode extension available; --fix flag auto-removes unused deps (knip.dev) |
eslint |
Unused vars, imports |
npx eslint --rule 'no-unused-vars: error' src/ |
|
| TypeScript compiler |
Unreachable code |
tsc --noUnusedLocals --noUnusedParameters |
|
depcheck |
Unused dependencies |
npx depcheck |
Still useful for a focused dep-only check |
ts-prune |
Unused exports |
npx ts-prune |
Archived Sep 19, 2025 — use knip instead (comparison & migration) |
Python
| Tool |
Detects |
Command |
vulture |
Unused code |
vulture src/ |
autoflake |
Unused imports/vars |
autoflake --check -r src/ |
pylint |
Unused vars, imports |
pylint --disable=all --enable=W0611,W0612 src/ |
flake8 |
Unused imports |
flake8 --select=F401 src/ |
pyflakes |
Unused imports/vars |
pyflakes src/ |
Go
| Tool |
Detects |
Command |
deadcode |
Unreachable functions |
deadcode ./... |
staticcheck |
Unused code patterns |
staticcheck ./... |
golangci-lint |
Multiple checks |
golangci-lint run --enable unused |
Rust
| Tool |
Detects |
Command |
cargo (built-in) |
Dead code warnings |
cargo build 2>&1 | grep "dead_code" |
cargo-udeps |
Unused dependencies |
cargo udeps |
Dead Code Categories
| Category |
Example |
Safe to Remove? |
| Unused local variable |
const unused = 1; |
Yes |
| Unused import |
import { unused } from './lib'; |
Yes |
| Commented-out code |
// oldFunction(); |
Yes |
| Console.log in production |
console.log('debug'); |
Yes |
| Unused private method |
private helper() {} |
Yes |
| Unused exported function |
export function unused() {} |
Check external usage |
| Unused public API |
public unusedMethod() {} |
May be called dynamically |
| Feature flag dead branch |
if (false) { ... } |
Confirm flag is permanent |
Safe Removal Checklist
Before removing code that appears dead:
Dead Code Cleanup Pattern
// Step 1: Identify unused code
// Run: npx ts-prune | grep -v "used in module"
// Step 2: Mark for removal (optional comment phase)
/** @deprecated Unused - scheduled for removal */
export function oldHelper() { ... }
// Step 3: Remove and verify
// Delete the code, run tests
// Step 4: Clean up imports
// Remove any import statements that reference deleted code
Language-Specific Patterns
TypeScript: Find Unused Exports
# knip — recommended replacement for ts-prune (archived Sep 2025)
npx knip
# Auto-fix unused deps and some exports
npx knip --fix
# CI: report findings without failing the build while cleaning up
npx knip --no-exit-code
Python: Remove Unused Imports
# Auto-fix with autoflake
autoflake --in-place --remove-all-unused-imports -r src/
# Preview only
autoflake --check -r src/
Go: Find Unreachable Functions
# golang.org/x/tools/cmd/deadcode
go install golang.org/x/tools/cmd/deadcode@latest
deadcode -test ./...
