Performance
Fallow is a compiled Rust binary with rayon-based parallelism. Knip runs on Node.js. Version 6 adopted the Oxc parser via NAPI bindings, which made it significantly faster than v5, but the single-threaded architecture remains.- Real-world projects
- Synthetic benchmarks
The speedup narrows on larger projects as analysis time dominates over startup overhead. On small-to-medium projects, fallow is 10—36x faster than knip v5 and 4—14x faster than knip v6. On 5,000+ file projects the gap is 2—3x. Fallow stays sub-second even at 5,000 files.
Why fallow is faster
| Factor | fallow | knip |
|---|---|---|
| Language | Compiled Rust binary | Node.js runtime |
| Parser | Oxc (native Rust) | Oxc via NAPI bindings |
| Parallelism | rayon work-stealing across all cores | Single-threaded |
| Startup | Instant (no JIT warmup) | Node.js bootstrap + module loading |
| Memory | Flat contiguous data structures | GC-managed heap |
Memory and large codebases
Fallow’s flat edge storage and lock-free parallel resolution are designed for large monorepos. Memory usage scales linearly with file count rather than with the Node.js GC heap.Detection capabilities
- Comparison table
- Details
| Capability | fallow | knip |
|---|---|---|
| Unused files | Yes | Yes |
| Unused exports | Yes | Yes |
| Unused types | Yes | Yes |
| Unused dependencies | Yes | Yes |
| Unused devDependencies | Yes | Yes |
| Unused enum members | Yes | Yes |
| Unused class members | Yes | No (dropped in v6) |
| Unresolved imports | Yes | Yes |
| Unlisted dependencies | Yes | Yes |
| Duplicate exports | Yes | No |
| Code duplication | Yes (fallow dupes) | No |
| Circular dependencies | Yes | Yes |
| Namespace members | No | Yes (new in v6) |
Plugin coverage
| Metric | fallow | knip |
|---|---|---|
| Total plugins | 84 | 141 |
| Plugins with config parsing | 31 | — |
| Custom plugin support | Yes (JSONC, JSON, TOML, or inline) | Yes (JS functions) |
If your project uses a framework that fallow doesn’t have a plugin for, you can create a custom plugin in JSONC, JSON, or TOML. No code required.
Features fallow has that knip doesn’t
SARIF output
Upload results directly to GitHub Code Scanning with
--format sarif. Integrated into your PR review workflow.Baseline comparison
--save-baseline and --baseline for incremental CI adoption. Only fail on new issues, not pre-existing ones.Inline suppression
// fallow-ignore-next-line and // fallow-ignore-file comments for granular, per-line suppression without config changes.Code duplication
Built-in
fallow dupes with four detection modes, clone family grouping, cross-language matching, and refactoring suggestions.Git-aware analysis
--changed-since analyzes only files changed since a git ref. Perfect for PR-only CI checks.Auto-fix dry run
Preview all fixes with
fallow fix --dry-run before applying. JSON output for programmatic review.Trace and debug tooling
--trace FILE:EXPORT to trace export usage chains, --trace-file PATH for file edges, --trace-dependency PACKAGE for dependency usage, --performance for pipeline timing.CSS Modules tracking
.module.css and .module.scss class names are extracted as named exports and tracked through styles.className member accesses.- Class member detection: Knip dropped this in v6; fallow retains it with decorator-aware skip logic for NestJS, Angular, TypeORM, etc.
- Production mode:
--productionexcludes test/dev files and detects type-only dependencies that should be devDependencies. - Duplicate export detection: Finds the same symbol exported from multiple modules.
- TOML configuration: In addition to JSONC/JSON, fallow supports
fallow.tomlfor teams that prefer TOML. - MCP server: Built-in MCP server (
fallow-mcp) for AI agent integration via the Model Context Protocol. - Cross-reference analysis:
check --include-dupesidentifies dead code that is also duplicated, surfacing high-priority cleanup targets.
Features knip has that fallow doesn’t
More plugins
141 plugins vs 84. Knip covers more niche, legacy, and ecosystem-specific tooling.
Custom reporters
Write custom reporter functions in JavaScript for fully custom output formatting.
Tags filtering
--tags flag filters results based on JSDoc @public/@internal annotations.- Codeowners reporter: Maps unused code to GitHub CODEOWNERS for targeted cleanup assignments.
- Namespace member detection: New in v6, detects unused members in TypeScript namespace declarations.
When to choose fallow
Speed matters
Large codebases where sub-second analysis enables watch mode and tight CI feedback loops.
CI pipelines
SARIF for GitHub Code Scanning, baselines for incremental adoption,
--changed-since for PR-scoped checks.Dead code + duplication
Replace both knip and jscpd with a single tool. Cross-reference dead code with duplication for prioritized cleanup.
Gradual adoption
Per-issue severity rules (
error/warn/off) and inline suppression comments let teams adopt incrementally.AI-assisted development
Your team uses AI coding agents. Fallow provides
--format json for CLI, an MCP server for typed tool calling, and --changed-since for PR-scoped checks.When to choose knip
Niche plugins
Your project depends on a specific tool that only knip has a plugin for, and a custom plugin isn’t worth the effort.
Already working well
Knip is already integrated and performance isn’t a pain point. No reason to migrate for the sake of it.
Custom reporters
You need fully custom output formatting via JavaScript reporter functions.
Summary table
| fallow | knip | |
|---|---|---|
| Language | Rust | Node.js (TypeScript) |
| Parser | Oxc (native) | Oxc (NAPI bindings) |
| Speed vs knip v6 | 2—14x faster | Baseline |
| Parallelism | Multi-core (rayon) | Single-threaded |
| Dead code issue types | 11 | 10 |
| Code duplication | Built-in | Not included |
| Plugins | 84 | 141 |
| Custom plugins | JSONC/JSON/TOML | JavaScript |
| SARIF output | Yes | No |
| Baseline comparison | Yes | No |
| Inline suppression | Yes | No |
Git-aware (--changed-since) | Yes | No |
| Circular dependencies | Yes | Yes |
| Auto-fix | Yes | Yes |
| Config formats | JSONC, JSON, TOML | JSON |
| Runtime dependency | None (standalone binary) | Node.js |
| MCP server | Built-in (fallow-mcp) | No |
Ready to switch?
If you’re coming from knip, fallow has a one-command migration path that automatically translates your configuration.Migrate from knip
Automatic config migration with
fallow migrate.Quick Start
Get started with fallow in 2 minutes.