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

# CEL

> Common Expression Language (CEL) is the syntax SafeDep uses for filters, queries, and policy rules over package data.

[Common Expression Language (CEL)](https://cel.dev/) is a safe, sandboxed expression language. SafeDep adopts it as the common syntax for filtering scan results, running queries, and writing policy rules. A CEL expression evaluates to true or false for each package, so you describe exactly which dependencies you care about.

## Why it matters

One language covers three jobs: ad-hoc filtering during a scan, repeatable queries over saved scan data, and enforceable policy. You learn the syntax once and reuse it everywhere.

## What you can reference

A CEL expression in Vet receives this data about each package:

| Variable    | What it holds                                                                                   |
| ----------- | ----------------------------------------------------------------------------------------------- |
| `pkg`       | Package coordinates: `ecosystem`, `name`, `version`                                             |
| `vulns`     | Vulnerabilities by severity: `all`, `critical`, `high`, `medium`, `low` (each item has an `id`) |
| `scorecard` | OpenSSF Scorecard data: `score` and per-check `scores["Check-Name"]`                            |
| `projects`  | Source projects: `name`, `type`, `stars`, `forks`, `issues`                                     |
| `licenses`  | SPDX license identifiers                                                                        |

A few expressions:

```cel theme={null}
vulns.critical.exists(x, true)
licenses.exists(p, p == "MIT")
projects.exists(x, x.stars < 100) && scorecard.scores.Maintained < 5
```

Hyphenated scorecard checks use the bracket form, for example `scorecard.scores["Token-Permissions"]`.

## Related

<CardGroup cols={2}>
  <Card title="Filtering" icon="filter" href="/reference/filtering">
    The full filter input structure and recipes.
  </Card>

  <Card title="Build Your Own Queries" icon="magnifying-glass" href="/reference/build-your-own-queries">
    Reuse CEL over saved scan data.
  </Card>

  <Card title="Policy" icon="file-shield" href="/concepts/policy">
    How CEL rules become enforceable policy.
  </Card>

  <Card title="Policy as Code" icon="file-code" href="/reference/policy-as-code">
    Write policy files with CEL.
  </Card>
</CardGroup>