# isLogLevelEnabled

**Kind:** Function

**Source:** [`packages/common/services/utils/is-log-level-enabled.util.ts`](https://github.com/nestjs/nest/blob/master/packages/common/services/utils/is-log-level-enabled.util.ts#L17)

**Part of:** [Common](subsystem-packages-common)

Checks if target level is enabled.

`isLogLevelEnabled` determines whether a target log level should be emitted based on the configured logger levels. It supports direct level matches and level-threshold behavior, allowing logging components to consistently filter messages before they are written.

## Signature

```ts
function isLogLevelEnabled(targetLevel: LogLevel, logLevels: LogLevel[] | undefined): boolean
```

## Parameters

| Name | Type |
|---|---|
| `targetLevel` | `LogLevel` |
| `logLevels` | `LogLevel[] | undefined` |

**Returns:** `boolean`

## Diagram

```mermaid
graph LR
  A[Target log level] --> C[isLogLevelEnabled]
  B[Configured log levels] --> C
  C --> D{Configuration exists?}
  D -- No --> E[Return false]
  D -- Yes --> F{Level explicitly enabled or allowed by threshold?}
  F -- Yes --> G[Return true]
  F -- No --> H[Return false]
```

## Usage

```ts
import { isLogLevelEnabled } from '@nestjs/common/services/utils/is-log-level-enabled.util';

const enabledLevels = ['debug'];

if (isLogLevelEnabled('log', enabledLevels)) {
  console.log('Application started');
}

if (isLogLevelEnabled('verbose', enabledLevels)) {
  console.log('Detailed diagnostic output');
}
```

## AI Coding Instructions

- Pass the requested log level as the first argument and the configured `LogLevel[]` collection as the second argument.
- Treat an empty or undefined configured level list as logging disabled; do not assume a default level is enabled.
- Reuse this utility before formatting or writing log messages to avoid unnecessary logging work.
- Preserve the established log-level ordering when changing supported levels, since threshold evaluation depends on that order.