Migrating from knip

Migrate from knip to fallow in minutes. One command converts your knip config. Fallow also covers duplication, complexity, and architecture boundaries that knip does not.

Fallow provides a one-command migration path from knip. Your existing configuration is automatically translated. Beyond what knip covers, fallow also detects code duplication, complexity hotspots, maintainability scores, and architecture boundary violations.

Migration workflow

1. Preview the migration

   Run fallow migrate --dry-run to see the generated config without writing anything:

   fallow migrate --dry-run
   

   Fallow searches for: knip.json, knip.jsonc, .knip.json, .knip.jsonc, knip.ts, knip.config.ts, and the knip field in package.json. TypeScript config files (knip.ts, knip.config.ts) are detected but cannot be parsed. Convert to knip.json first.

   $ fallow migrate --dry-run

   Detected knip config: knip.json
   
   Migrating settings:
     entry          → entry: ["src/index.ts", "src/cli.ts"]
     ignore         → ignorePatterns: ["**/*.generated.ts"]
     ignoreDeps     → ignoreDependencies: ["@types/node"]
   
   ⚠ Cannot migrate:
     ignoreBinaries → not applicable in fallow
   
   Would write: .fallowrc.json
   Run without --dry-run to write the config.
   
2. Generate the config

   Once you’re happy with the preview, run the migration:

   fallow migrate            # Write .fallowrc.json
   fallow migrate --toml     # Or output as fallow.toml
   
3. Review the config

   Open the generated config and verify the translated entry points, ignore patterns, and plugin mappings. Warnings are shown for any fields that couldn’t be migrated automatically.

4. Run your first analysis

   Run dead code analysis and compare results against knip. Then explore the other analyses that knip does not cover:

   fallow dead-code    # Unused code + circular deps + boundaries
   fallow dupes        # Code duplication
   fallow health       # Complexity hotspots + maintainability scores
   fallow              # All of the above in one pass
   

What gets migrated

knip	fallow
entry	entry
project	— (fallow auto-discovers project files)
ignore	ignorePatterns
ignoreDependencies	ignoreDependencies
ignoreExportsUsedInFile	ignoreExportsUsedInFile (boolean and { type, interface } object form both supported)
ignoreBinaries	— (not applicable)
Plugin configs	Closest fallow plugin equivalent

Warnings and caveats

fallow migrate is loud about anything it cannot translate so the migration is not silently lossy.

Unknown rule names. If your knip rules, exclude, or include entries reference a key that fallow does not know (typo, future knip rule, or an issue type the migrator has not yet catalogued), the migration emits a warning like:

Warning (1 skipped field):
  [knip] `rules.unsued-files`: unknown knip issue type `unsued-files`; not migrated
  (suggestion: check for a typo or report the missing mapping at https://docs.fallow.tools/migration/from-knip)

If the key is in the documented unmappable list (binaries, optionalPeerDependencies, and similar issue types knip emits but fallow does not), the warning reads issue type \X` has no fallow equivalent` and has no suggestion.

Glob-engine drift. Knip and fallow use different glob engines, so entry and ignorePatterns are copied verbatim but may match a slightly different file set than they did under knip. When the migrated config carries either field, the migrate command prints:

Note: knip and fallow use different glob engines; verify migrated entry / ignorePatterns
      with `fallow check` before relying on CI. See https://docs.fallow.tools/migration/from-knip

Common patterns (brace expansion {ts,tsx}, double-star **, src/**) match identically across both engines. Known drift today: fallow’s ignorePatterns does not honor leading ! as negation; entries are matched literally. Run fallow check on a representative subset before relying on the migrated globs in CI.

Comparison

Speed

Fallow is a Rust-native standalone binary. No Node.js runtime, no JIT warmup, no garbage collection pauses.

Metric	fallow	knip
Speed vs knip v5	3—36x faster	Baseline
Speed vs knip v6	2—14x faster	Baseline
Memory usage	3—11x less	Baseline
Runtime dependency	None (standalone binary)	Node.js
CI setup	Download binary	Install Node + npm dependencies

Features

Feature	fallow	knip
Duplication detection	Built-in (fallow dupes)	Not included
SARIF output	Yes	No
Baseline comparison	Yes (--baseline)	No
Git-aware analysis	--changed-since	No
Production mode	--production	No
Auto-fix	Exports + dependencies	Exports + dependencies
Config format	JSONC, JSON, TOML	JSON, TS

Coverage

Metric	fallow	knip
Framework plugins	94 (39 with config parsing)	141
Dead code issue types	15	10
Custom plugins	Yes	Yes

Key differences

No runtime dependency

Fallow is a standalone binary. No Node.js runtime, no dependency conflicts, faster CI setup.

See also

Custom plugins

Build plugins for frameworks fallow doesn’t cover yet.

fallow migrate

Full CLI reference for the migrate command.