diff --git a/docs/config/api.md b/docs/config/api.md
index 6bf6ea6e924d..8c973dbbd94e 100644
--- a/docs/config/api.md
+++ b/docs/config/api.md
@@ -9,7 +9,7 @@ outline: deep
 - **Default:** `false`
 - **CLI:** `--api`, `--api.port`, `--api.host`, `--api.strictPort`
 
-Listen to port and serve API for [the UI](/guide/ui) or [browser server](/guide/browser/). When set to `true`, the default port is `51204` or `63315` if running in Browser Mode.
+Listen to port and serve API for [the UI](/guide/ui) or [browser server](/guide/browser/). When set to `true`, the default port is `51204` or `23315` if running in Browser Mode.
 
 In Browser Mode the server binds its port on the first browser launch, unless `api` or `ui` is enabled.
 
diff --git a/docs/guide/browser/index.md b/docs/guide/browser/index.md
index e2fe7349e7a3..ccc3061d7e3a 100644
--- a/docs/guide/browser/index.md
+++ b/docs/guide/browser/index.md
@@ -138,7 +138,7 @@ export default defineConfig({
 ```
 
 ::: info
-Vitest assigns port `63315` to avoid conflicts with the development server, allowing you to run both in parallel. You can change that with the [`api`](/config/api) option. The port is bound when the first browser is launched, or on startup if `api` or `ui` is enabled.
+Vitest assigns port `23315` to avoid conflicts with the development server, allowing you to run both in parallel. You can change that with the [`api`](/config/api) option. The port is bound when the first browser is launched, or on startup if `api` or `ui` is enabled.
 :::
 
 If you have not used Vite before, make sure you have your framework's plugin installed and specified in the config. Some frameworks might require extra configuration to work - check their Vite related documentation to be sure.
diff --git a/docs/guide/migration/index.md b/docs/guide/migration/index.md
index cdd4e25723db..8ea3253b7c54 100644
--- a/docs/guide/migration/index.md
+++ b/docs/guide/migration/index.md
@@ -531,7 +531,7 @@ If you manually opened the browser preview by copying the Vite server URL or vis
 
 ## `browser.api` Is Replaced by the Top-Level `api`
 
-Browser mode now runs on a single Vite server configured by the top-level [`api`](/config/api) option; the default port in browser mode is still `63315`. The `browser.api` option is deprecated and no longer has any effect, so move its value to `api`:
+Browser mode now runs on a single Vite server configured by the top-level [`api`](/config/api) option; the default port in browser mode is `23315`. The `browser.api` option is deprecated and no longer has any effect, so move its value to `api`:
 
 ```ts [vitest.config.ts]
 import { defineConfig } from 'vitest/config'
diff --git a/packages/ui/CONTRIBUTING.md b/packages/ui/CONTRIBUTING.md
index 7fa4e62d9ffa..590c844aff66 100644
--- a/packages/ui/CONTRIBUTING.md
+++ b/packages/ui/CONTRIBUTING.md
@@ -49,7 +49,7 @@ BROWSER_DEV=true pnpm -C packages/ui dev:client
 
 Open the URL printed by the UI dev server, usually `http://localhost:5173/`.
 
-The UI dev server fetches browser runner state from the browser runner server on port `63315` by default. If Vitest prints a different browser runner port, pass it to the UI dev server:
+The UI dev server fetches browser runner state from the browser runner server on port `23315` by default. If Vitest prints a different browser runner port, pass it to the UI dev server:
 
 ```bash
 BROWSER_DEV_PORT=63316 BROWSER_DEV=true pnpm -C packages/ui dev:client
diff --git a/packages/ui/vite.config.ts b/packages/ui/vite.config.ts
index 5b20a39018ed..367da7d73553 100644
--- a/packages/ui/vite.config.ts
+++ b/packages/ui/vite.config.ts
@@ -69,7 +69,7 @@ function devUiScriptPlugin(): Plugin {
   const BROWSER_SCRIPT_RE =
     /<script type="module">([\s\S]*?window\.__vitest_browser_runner__\s*=\s*\{[\s\S]*?window\.VITEST_API_TOKEN\s*=[\s\S]*?)<\/script>/
 
-  const browserUrl = `http://localhost:${process.env.BROWSER_DEV_PORT || '63315'}/__vitest_test__/`
+  const browserUrl = `http://localhost:${process.env.BROWSER_DEV_PORT || '23315'}/__vitest_test__/`
 
   return {
     name: 'dev-ui-script',
diff --git a/packages/vitest/src/constants.ts b/packages/vitest/src/constants.ts
index ccf371255794..d94cc317e553 100644
--- a/packages/vitest/src/constants.ts
+++ b/packages/vitest/src/constants.ts
@@ -1,6 +1,6 @@
 // if changed, update also jsdocs and docs
 export const defaultPort = 51204
-export const defaultBrowserPort = 63315
+export const defaultBrowserPort = 23315
 export const defaultInspectPort = 9229
 
 export const API_PATH = '/__vitest_api__'
diff --git a/test/browser/specs/browser-multiple.test.ts b/test/browser/specs/browser-multiple.test.ts
index 0acd54255a6b..52bc5e06c6c0 100644
--- a/test/browser/specs/browser-multiple.test.ts
+++ b/test/browser/specs/browser-multiple.test.ts
@@ -27,6 +27,6 @@ it('automatically assigns the port', async () => {
 
   expect(spy).not.toHaveBeenCalled()
   expect(stderr).not.toContain('is in use, trying another one...')
-  expect(urls).toContain('http://localhost:63315/')
-  expect(urls).toContain('http://localhost:63316/')
+  expect(urls).toContain('http://localhost:23315/')
+  expect(urls).toContain('http://localhost:23316/')
 })