---
id: api/node-events/before-run-api
title: 'before:run event'
description: 'The before:run event fires before a run starts in Cypress.'
section: api
source_path: docs/api/node-events/before-run-api.mdx
version: 2069658b67bb86b8923569761b9bda5eebc57aff
updated_at: '2026-08-25T16:55:04.655Z'
---
# Before Run Event

The `before:run` event fires before a run starts. When running cypress via `cypress open`, the event will fire when opening a project.

The event will fire each time `cypress run` executes. As a result, if running your specs in [parallel](/llm/markdown/cloud/features/smart-orchestration/parallelization.md), the event will fire once for each machine on which the tests are run.

## Syntax

⚠️ This code is part of the [setupNodeEvents](/llm/markdown/app/plugins/plugins-guide.md#Using-a-plugin) function and thus executes in the Node environment. You cannot call `Cypress` or `cy` commands in this function, but you do have the direct access to the file system and the rest of the operating system.

⚠️ When running via `cypress open`, the `before:run` event only fires if the [experimentalInteractiveRunEvents flag](/llm/markdown/app/references/experiments.md#Configuration) is enabled.

*   cypress.config.js
*   cypress.config.ts

```
const { defineConfig } = require('cypress')

module.exports = defineConfig({
  // setupNodeEvents can be defined in either
  // the e2e or component configuration
  e2e: {
    setupNodeEvents(on, config) {
      on('before:run', (details) => {
        /* ... */
      })
    },
  },
})
```

```
import { defineConfig } from 'cypress'

export default defineConfig({
  // setupNodeEvents can be defined in either
  // the e2e or component configuration
  e2e: {
    setupNodeEvents(on, config) {
      on('before:run', (details) => {
        /* ... */
      })
    },
  },
})
```

**details _(Object)_**

Details of the run, including the project config, system information, and the version of Cypress. More details are included when running via `cypress run`.

## Usage

You can return a promise from the `before:run` event handler and it will be awaited before Cypress proceeds running your specs.

### Log the browser and the number of specs that will be run

*   cypress.config.js
*   cypress.config.ts

```
const { defineConfig } = require('cypress')

module.exports = defineConfig({
  // setupNodeEvents can be defined in either
  // the e2e or component configuration
  e2e: {
    setupNodeEvents(on, config) {
      on('before:run', (details) => {
        // details will look something like this when run via `cypress run`:
        // {
        //   config: {
        //     projectId: '12345',
        //     baseUrl: 'http://example.com/',
        //     viewportWidth: 1000,
        //     viewportHeight: 660,
        //     // ...more properties...
        //   },
        //   browser: {
        //     name: 'electron',
        //     version: '59.0.3071.115',
        //     // ...more properties...
        //   },
        //   system: {
        //     osName: 'darwin',
        //     osVersion: '16.7.0',
        //   }
        //   cypressVersion: '6.1.0',
        //   specs: [
        //     {
        //       name: 'login_cy.js',
        //       relative: 'cypress/e2e/login_cy.js',
        //       absolute: '/Users/janelane/app/cypress/e2e/login_cy.js',
        //     },
        //     // ... more specs
        //   ],
        //   specPattern: [
        //     '**/*.cy.{js,jsx,ts,tsx}'
        //   ],
        //   parallel: false,
        //   group: 'group-1',
        //   tag: 'tag-1'
        // }
        // details will look something like this when run via `cypress open`:
        // {
        //   config: {
        //     projectId: '12345',
        //     baseUrl: 'http://example.com/',
        //     viewportWidth: 1000,
        //     viewportHeight: 660,
        //     // ...more properties...
        //   },
        //   system: {
        //     osName: 'darwin',
        //     osVersion: '16.7.0',
        //   }
        //   cypressVersion: '7.0.0'
        // }
        if (details.specs && details.browser) {
          // details.specs and details.browser will be undefined in interactive mode
          console.log(
            'Running',
            details.specs.length,
            'specs in',
            details.browser.name
          )
        }
      })
    },
  },
})
```

```
import { defineConfig } from 'cypress'

export default defineConfig({
  // setupNodeEvents can be defined in either
  // the e2e or component configuration
  e2e: {
    setupNodeEvents(on, config) {
      on('before:run', (details) => {
        // details will look something like this when run via `cypress run`:
        // {
        //   config: {
        //     projectId: '12345',
        //     baseUrl: 'http://example.com/',
        //     viewportWidth: 1000,
        //     viewportHeight: 660,
        //     // ...more properties...
        //   },
        //   browser: {
        //     name: 'electron',
        //     version: '59.0.3071.115',
        //     // ...more properties...
        //   },
        //   system: {
        //     osName: 'darwin',
        //     osVersion: '16.7.0',
        //   }
        //   cypressVersion: '6.1.0',
        //   specs: [
        //     {
        //       name: 'login_cy.js',
        //       relative: 'cypress/e2e/login_cy.js',
        //       absolute: '/Users/janelane/app/cypress/e2e/login_cy.js',
        //     },
        //     // ... more specs
        //   ],
        //   specPattern: [
        //     '**/*.cy.{js,jsx,ts,tsx}'
        //   ],
        //   parallel: false,
        //   group: 'group-1',
        //   tag: 'tag-1'
        // }
        // details will look something like this when run via `cypress open`:
        // {
        //   config: {
        //     projectId: '12345',
        //     baseUrl: 'http://example.com/',
        //     viewportWidth: 1000,
        //     viewportHeight: 660,
        //     // ...more properties...
        //   },
        //   system: {
        //     osName: 'darwin',
        //     osVersion: '16.7.0',
        //   }
        //   cypressVersion: '7.0.0'
        // }
        if (details.specs && details.browser) {
          // details.specs and details.browser will be undefined in interactive mode
          console.log(
            'Running',
            details.specs.length,
            'specs in',
            details.browser.name
          )
        }
      })
    },
  },
})
```

## See also

*   [After Run API](/llm/markdown/api/node-events/after-run-api.md)
*   [Before Spec API](/llm/markdown/api/node-events/before-spec-api.md)
*   [After Spec API](/llm/markdown/api/node-events/after-spec-api.md)
*   [How to use Plugins](/llm/markdown/app/plugins/plugins-guide.md)
*   [Node Events Overview](/llm/markdown/api/node-events/overview.md)