Fallow review
A free TypeScript and JavaScript duplication scanner with CI gates and optional paid runtime insights.
Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026
Fallow is a codebase analysis tool for TypeScript and JavaScript projects, suited to developers and teams who want duplication checks in their everyday workflow or CI. Its free MIT scan detects duplicated code alongside dead code, complexity, dependency, and architecture issues. It runs from the terminal, in CI, in VS Code, or with coding agents, so teams can choose an existing development workflow rather than relying on a single interface. The language scope is specific: clone comparisons can cross between TypeScript and JavaScript files, but the tool is not positioned for projects in other languages.
Duplication analysis has several levels: strict, mild, weak, and semantic modes, with optional near-miss detection for function-scoped clones that have small structural edits. Fallow ranks clone groups, and teams can set a duplication percentage threshold to fail a run. Baseline comparison can fail only on new duplication, while changed-since analysis reports duplication introduced by changes. JSON, SARIF, Markdown, compact, and CodeClimate output give teams options for incorporating findings into CI and reporting workflows; listed integrations include GitHub Actions, GitLab CI, VS Code, and MCP. This makes the free product a fit for teams that want a duplication gate without paying for runtime insights.
According to the published plans, Fallow Free, MIT costs nothing. Fallow Runtime starts at $20 per seat per month, billed monthly, and adds production function-call counts, a dashboard with deployment history, and email alerts. The 30-day Runtime trial requires no credit card. Enterprise includes Runtime features, security review assistance, and invoice payment and contract terms on request. Choose Fallow if TypeScript and JavaScript coverage and CI-focused duplication analysis match your needs; consider another tool if your codebase requires other languages. Runtime is relevant when production call data is also a requirement, rather than just static duplication scanning.
Fallow pros and cons
- Where it wins
- Free MIT scan runs in the terminal, CI, VS Code, and coding agents
- Baseline and changed-since analysis can focus CI checks on new duplication
- Multiple detection modes, near-miss analysis, and CI output formats
- Where it doesn't
- Analysis is limited to TypeScript and JavaScript projects
- Near-miss detection is limited to function-scoped clones with small structural edits
- Production function-call data requires the separate paid Runtime service
Fallow fact sheet, pricing and score →
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