> ## Documentation Index
> Fetch the complete documentation index at: https://docs.fallow.tools/llms.txt
> Use this file to discover all available pages before exploring further.

# Migrating from jscpd

> Migrate from jscpd to fallow for 8-26x faster duplication detection. One command converts your jscpd config. Also covers unused code, complexity, circular dependencies, and architecture boundaries.

Fallow replaces jscpd with a faster, more capable duplication engine. It also covers unused code detection, complexity analysis, circular dependencies, and architecture boundaries in the same binary.

## Migration workflow

<Steps>
  <Step title="Preview the migration">
    Run `fallow migrate --dry-run` to see the generated config without writing anything:

    ```bash theme={null}
    fallow migrate --dry-run
    ```

    Fallow searches for `.jscpd.json` and the `jscpd` field in `package.json`.
  </Step>

  <Step title="Generate the config">
    Once you're happy with the preview, run the migration:

    ```bash theme={null}
    fallow migrate            # Write .fallowrc.json
    fallow migrate --toml     # Or output as fallow.toml
    ```
  </Step>

  <Step title="Review the config">
    Open the generated config and verify the translated thresholds, token counts, and ignore patterns.
  </Step>

  <Step title="Run fallow dupes">
    Run your first duplication analysis:

    ```bash theme={null}
    fallow dupes
    ```
  </Step>
</Steps>

<Tip>
  The default `mild` mode normalizes syntax variations and may flag more clones than jscpd did. For results closest to jscpd's exact token matching, use `--mode strict`.
</Tip>

## What gets migrated

| jscpd       | fallow                             |
| :---------- | :--------------------------------- |
| `threshold` | `duplicates.threshold`             |
| `minTokens` | `duplicates.minTokens`             |
| `minLines`  | `duplicates.minLines`              |
| `ignore`    | `ignorePatterns`                   |
| `format`    | -- (fallow auto-detects languages) |

## Comparison

|                              | fallow                            | jscpd                   |
| :--------------------------- | :-------------------------------- | :---------------------- |
| Speed (real-world)           | **8--26x faster**                 | Baseline                |
| Detection modes              | 4 (strict, mild, weak, semantic)  | 1 (token-based)         |
| Algorithm                    | Suffix array with LCP             | Rabin-Karp rolling hash |
| Unused code + circular deps  | Built-in (`fallow dead-code`)     | Not included            |
| Complexity + maintainability | Built-in (`fallow health`)        | Not included            |
| Clone families               | Yes, with refactoring suggestions | No                      |
| Cross-language               | TS to JS type stripping           | Format-based            |
| Baseline tracking            | Yes                               | No                      |
| Runtime dependency           | None                              | Node.js                 |

## Detection mode mapping

jscpd uses a single token-based detection mode. The closest fallow equivalent is `strict`, which performs exact token matching.

Fallow defaults to `mild` mode, which normalizes syntax variations and may flag more clones than jscpd did. To match jscpd's behavior more closely, use `strict` mode:

```bash theme={null}
fallow dupes --mode strict
```

For broader matching that catches renamed variables:

```bash theme={null}
fallow dupes --mode semantic
```

## One tool for the full picture

<Check>
  Fallow covers unused code, duplication, complexity hotspots, circular dependencies, and architecture boundaries in a single binary. It replaces jscpd, knip, and madge.
</Check>

```bash theme={null}
fallow dead-code    # Unused code + circular deps + boundaries
fallow dupes        # Code duplication (replaces jscpd)
fallow health       # Complexity hotspots + maintainability scores
fallow              # All of the above in one pass
```

## See also

<CardGroup cols={2}>
  <Card title="Duplication analysis" icon="clone" href="/analysis/duplication">
    Deep dive into fallow's duplication detection engine.
  </Card>

  <Card title="fallow dupes" icon="terminal" href="/cli/dupes">
    Full CLI reference for the dupes command.
  </Card>
</CardGroup>