---
id: api/node-events/before-run-api
title: Before Run Event | Cypress Node Events
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: 524ff5211e60b5d53e55d6ad976d83966f66e7cd
updated_at: '2026-04-30T14:20:05.396Z'
---
# 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)