diff --git a/.changeset/unlucky-sheep-build.md b/.changeset/unlucky-sheep-build.md
new file mode 100644
index 000000000..6a69876de
--- /dev/null
+++ b/.changeset/unlucky-sheep-build.md
@@ -0,0 +1,7 @@
+---
+'astro': major
+---
+
+Astro's default port when running the dev or preview server is now `4321`.
+
+This will reduce conflicts with ports used by other tools.
diff --git a/.devcontainer/basics/devcontainer.json b/.devcontainer/basics/devcontainer.json
index 0a57f37ce..bb1707ff0 100644
--- a/.devcontainer/basics/devcontainer.json
+++ b/.devcontainer/basics/devcontainer.json
@@ -7,13 +7,13 @@
   "workspaceFolder": "/workspaces/astro/examples/basics",
 
   "portsAttributes": {
-    "3000": {
+    "4321": {
       "label": "Application",
       "onAutoForward": "openPreview"
     }
   },
 
-  "forwardPorts": [3000],
+  "forwardPorts": [4321],
 
   "postCreateCommand": "pnpm install && cd /workspaces/astro && pnpm run build",
 
diff --git a/.devcontainer/blog/devcontainer.json b/.devcontainer/blog/devcontainer.json
index 165683a7d..d587fead5 100644
--- a/.devcontainer/blog/devcontainer.json
+++ b/.devcontainer/blog/devcontainer.json
@@ -7,13 +7,13 @@
   "workspaceFolder": "/workspaces/astro/examples/blog",
 
   "portsAttributes": {
-    "3000": {
+    "4321": {
       "label": "Application",
       "onAutoForward": "openPreview"
     }
   },
 
-  "forwardPorts": [3000],
+  "forwardPorts": [4321],
 
   "postCreateCommand": "pnpm install && cd /workspaces/astro && pnpm run build",
 
diff --git a/.devcontainer/deno/devcontainer.json b/.devcontainer/deno/devcontainer.json
index 2df23782f..05b733527 100644
--- a/.devcontainer/deno/devcontainer.json
+++ b/.devcontainer/deno/devcontainer.json
@@ -7,13 +7,13 @@
   "workspaceFolder": "/workspaces/astro/examples/deno",
 
   "portsAttributes": {
-    "3000": {
+    "4321": {
       "label": "Application",
       "onAutoForward": "openPreview"
     }
   },
 
-  "forwardPorts": [3000],
+  "forwardPorts": [4321],
 
   "postCreateCommand": "pnpm install && cd /workspaces/astro && pnpm run build",
 
diff --git a/.devcontainer/docs/devcontainer.json b/.devcontainer/docs/devcontainer.json
index 281fd614e..a26ff9d8c 100644
--- a/.devcontainer/docs/devcontainer.json
+++ b/.devcontainer/docs/devcontainer.json
@@ -7,13 +7,13 @@
   "workspaceFolder": "/workspaces/astro/examples/docs",
 
   "portsAttributes": {
-    "3000": {
+    "4321": {
       "label": "Application",
       "onAutoForward": "openPreview"
     }
   },
 
-  "forwardPorts": [3000],
+  "forwardPorts": [4321],
 
   "postCreateCommand": "pnpm install && cd /workspaces/astro && pnpm run build",
 
diff --git a/.devcontainer/framework-alpine/devcontainer.json b/.devcontainer/framework-alpine/devcontainer.json
index f96022532..1b8f26503 100644
--- a/.devcontainer/framework-alpine/devcontainer.json
+++ b/.devcontainer/framework-alpine/devcontainer.json
@@ -7,13 +7,13 @@
   "workspaceFolder": "/workspaces/astro/examples/framework-alpine",
 
   "portsAttributes": {
-    "3000": {
+    "4321": {
       "label": "Application",
       "onAutoForward": "openPreview"
     }
   },
 
-  "forwardPorts": [3000],
+  "forwardPorts": [4321],
 
   "postCreateCommand": "pnpm install && cd /workspaces/astro && pnpm run build",
 
diff --git a/.devcontainer/framework-lit/devcontainer.json b/.devcontainer/framework-lit/devcontainer.json
index bdceda2d3..4eb1d5979 100644
--- a/.devcontainer/framework-lit/devcontainer.json
+++ b/.devcontainer/framework-lit/devcontainer.json
@@ -7,13 +7,13 @@
   "workspaceFolder": "/workspaces/astro/examples/framework-lit",
 
   "portsAttributes": {
-    "3000": {
+    "4321": {
       "label": "Application",
       "onAutoForward": "openPreview"
     }
   },
 
-  "forwardPorts": [3000],
+  "forwardPorts": [4321],
 
   "postCreateCommand": "pnpm install && cd /workspaces/astro && pnpm run build",
 
diff --git a/.devcontainer/framework-multiple/devcontainer.json b/.devcontainer/framework-multiple/devcontainer.json
index cdaa417a3..660df3e32 100644
--- a/.devcontainer/framework-multiple/devcontainer.json
+++ b/.devcontainer/framework-multiple/devcontainer.json
@@ -7,13 +7,13 @@
   "workspaceFolder": "/workspaces/astro/examples/framework-multiple",
 
   "portsAttributes": {
-    "3000": {
+    "4321": {
       "label": "Application",
       "onAutoForward": "openPreview"
     }
   },
 
-  "forwardPorts": [3000],
+  "forwardPorts": [4321],
 
   "postCreateCommand": "pnpm install && cd /workspaces/astro && pnpm run build",
 
diff --git a/.devcontainer/framework-preact/devcontainer.json b/.devcontainer/framework-preact/devcontainer.json
index e0ce8771c..5c71cb6f2 100644
--- a/.devcontainer/framework-preact/devcontainer.json
+++ b/.devcontainer/framework-preact/devcontainer.json
@@ -7,13 +7,13 @@
   "workspaceFolder": "/workspaces/astro/examples/framework-preact",
 
   "portsAttributes": {
-    "3000": {
+    "4321": {
       "label": "Application",
       "onAutoForward": "openPreview"
     }
   },
 
-  "forwardPorts": [3000],
+  "forwardPorts": [4321],
 
   "postCreateCommand": "pnpm install && cd /workspaces/astro && pnpm run build",
 
diff --git a/.devcontainer/framework-react/devcontainer.json b/.devcontainer/framework-react/devcontainer.json
index 07404950f..f130c26ff 100644
--- a/.devcontainer/framework-react/devcontainer.json
+++ b/.devcontainer/framework-react/devcontainer.json
@@ -7,13 +7,13 @@
   "workspaceFolder": "/workspaces/astro/examples/framework-react",
 
   "portsAttributes": {
-    "3000": {
+    "4321": {
       "label": "Application",
       "onAutoForward": "openPreview"
     }
   },
 
-  "forwardPorts": [3000],
+  "forwardPorts": [4321],
 
   "postCreateCommand": "pnpm install && cd /workspaces/astro && pnpm run build",
 
diff --git a/.devcontainer/framework-solid/devcontainer.json b/.devcontainer/framework-solid/devcontainer.json
index f3cf86d80..4a3e65ec8 100644
--- a/.devcontainer/framework-solid/devcontainer.json
+++ b/.devcontainer/framework-solid/devcontainer.json
@@ -7,13 +7,13 @@
   "workspaceFolder": "/workspaces/astro/examples/framework-solid",
 
   "portsAttributes": {
-    "3000": {
+    "4321": {
       "label": "Application",
       "onAutoForward": "openPreview"
     }
   },
 
-  "forwardPorts": [3000],
+  "forwardPorts": [4321],
 
   "postCreateCommand": "pnpm install && cd /workspaces/astro && pnpm run build",
 
diff --git a/.devcontainer/framework-svelte/devcontainer.json b/.devcontainer/framework-svelte/devcontainer.json
index 7ea52458d..d8db14287 100644
--- a/.devcontainer/framework-svelte/devcontainer.json
+++ b/.devcontainer/framework-svelte/devcontainer.json
@@ -7,13 +7,13 @@
   "workspaceFolder": "/workspaces/astro/examples/framework-svelte",
 
   "portsAttributes": {
-    "3000": {
+    "4321": {
       "label": "Application",
       "onAutoForward": "openPreview"
     }
   },
 
-  "forwardPorts": [3000],
+  "forwardPorts": [4321],
 
   "postCreateCommand": "pnpm install && cd /workspaces/astro && pnpm run build",
 
diff --git a/.devcontainer/framework-vue/devcontainer.json b/.devcontainer/framework-vue/devcontainer.json
index 9caae267a..db9a62878 100644
--- a/.devcontainer/framework-vue/devcontainer.json
+++ b/.devcontainer/framework-vue/devcontainer.json
@@ -7,13 +7,13 @@
   "workspaceFolder": "/workspaces/astro/examples/framework-vue",
 
   "portsAttributes": {
-    "3000": {
+    "4321": {
       "label": "Application",
       "onAutoForward": "openPreview"
     }
   },
 
-  "forwardPorts": [3000],
+  "forwardPorts": [4321],
 
   "postCreateCommand": "pnpm install && cd /workspaces/astro && pnpm run build",
 
diff --git a/.devcontainer/hackernews/devcontainer.json b/.devcontainer/hackernews/devcontainer.json
index 384c9035a..dc113624d 100644
--- a/.devcontainer/hackernews/devcontainer.json
+++ b/.devcontainer/hackernews/devcontainer.json
@@ -7,13 +7,13 @@
   "workspaceFolder": "/workspaces/astro/examples/hackernews",
 
   "portsAttributes": {
-    "3000": {
+    "4321": {
       "label": "Application",
       "onAutoForward": "openPreview"
     }
   },
 
-  "forwardPorts": [3000],
+  "forwardPorts": [4321],
 
   "postCreateCommand": "pnpm install && cd /workspaces/astro && pnpm run build",
 
diff --git a/.devcontainer/minimal/devcontainer.json b/.devcontainer/minimal/devcontainer.json
index 877030ef8..1756ffd8b 100644
--- a/.devcontainer/minimal/devcontainer.json
+++ b/.devcontainer/minimal/devcontainer.json
@@ -7,13 +7,13 @@
   "workspaceFolder": "/workspaces/astro/examples/minimal",
 
   "portsAttributes": {
-    "3000": {
+    "4321": {
       "label": "Application",
       "onAutoForward": "openPreview"
     }
   },
 
-  "forwardPorts": [3000],
+  "forwardPorts": [4321],
 
   "postCreateCommand": "pnpm install && cd /workspaces/astro && pnpm run build",
 
diff --git a/.devcontainer/non-html-pages/devcontainer.json b/.devcontainer/non-html-pages/devcontainer.json
index f5d979d87..b47fae4e9 100644
--- a/.devcontainer/non-html-pages/devcontainer.json
+++ b/.devcontainer/non-html-pages/devcontainer.json
@@ -7,13 +7,13 @@
   "workspaceFolder": "/workspaces/astro/examples/non-html-pages",
 
   "portsAttributes": {
-    "3000": {
+    "4321": {
       "label": "Application",
       "onAutoForward": "openPreview"
     }
   },
 
-  "forwardPorts": [3000],
+  "forwardPorts": [4321],
 
   "postCreateCommand": "pnpm install && cd /workspaces/astro && pnpm run build",
 
diff --git a/.devcontainer/portfolio/devcontainer.json b/.devcontainer/portfolio/devcontainer.json
index c082b8306..39e283d83 100644
--- a/.devcontainer/portfolio/devcontainer.json
+++ b/.devcontainer/portfolio/devcontainer.json
@@ -7,13 +7,13 @@
   "workspaceFolder": "/workspaces/astro/examples/portfolio",
 
   "portsAttributes": {
-    "3000": {
+    "4321": {
       "label": "Application",
       "onAutoForward": "openPreview"
     }
   },
 
-  "forwardPorts": [3000],
+  "forwardPorts": [4321],
 
   "postCreateCommand": "pnpm install && cd /workspaces/astro && pnpm run build",
 
diff --git a/.devcontainer/ssr/devcontainer.json b/.devcontainer/ssr/devcontainer.json
index acca0937c..2ace9a1dd 100644
--- a/.devcontainer/ssr/devcontainer.json
+++ b/.devcontainer/ssr/devcontainer.json
@@ -7,13 +7,13 @@
   "workspaceFolder": "/workspaces/astro/examples/ssr",
 
   "portsAttributes": {
-    "3000": {
+    "4321": {
       "label": "Application",
       "onAutoForward": "openPreview"
     }
   },
 
-  "forwardPorts": [3000],
+  "forwardPorts": [4321],
 
   "postCreateCommand": "pnpm install && cd /workspaces/astro && pnpm run build",
 
diff --git a/.devcontainer/with-markdown-plugins/devcontainer.json b/.devcontainer/with-markdown-plugins/devcontainer.json
index bb7d7c28e..21894a77c 100644
--- a/.devcontainer/with-markdown-plugins/devcontainer.json
+++ b/.devcontainer/with-markdown-plugins/devcontainer.json
@@ -7,13 +7,13 @@
   "workspaceFolder": "/workspaces/astro/examples/with-markdown-plugins",
 
   "portsAttributes": {
-    "3000": {
+    "4321": {
       "label": "Application",
       "onAutoForward": "openPreview"
     }
   },
 
-  "forwardPorts": [3000],
+  "forwardPorts": [4321],
 
   "postCreateCommand": "pnpm install && cd /workspaces/astro && pnpm run build",
 
diff --git a/.devcontainer/with-markdown-shiki/devcontainer.json b/.devcontainer/with-markdown-shiki/devcontainer.json
index 0b1d04188..a3f51750a 100644
--- a/.devcontainer/with-markdown-shiki/devcontainer.json
+++ b/.devcontainer/with-markdown-shiki/devcontainer.json
@@ -7,13 +7,13 @@
   "workspaceFolder": "/workspaces/astro/examples/with-markdown-shiki",
 
   "portsAttributes": {
-    "3000": {
+    "4321": {
       "label": "Application",
       "onAutoForward": "openPreview"
     }
   },
 
-  "forwardPorts": [3000],
+  "forwardPorts": [4321],
 
   "postCreateCommand": "pnpm install && cd /workspaces/astro && pnpm run build",
 
diff --git a/.devcontainer/with-mdx/devcontainer.json b/.devcontainer/with-mdx/devcontainer.json
index add8d32da..13ff67464 100644
--- a/.devcontainer/with-mdx/devcontainer.json
+++ b/.devcontainer/with-mdx/devcontainer.json
@@ -7,13 +7,13 @@
   "workspaceFolder": "/workspaces/astro/examples/with-mdx",
 
   "portsAttributes": {
-    "3000": {
+    "4321": {
       "label": "Application",
       "onAutoForward": "openPreview"
     }
   },
 
-  "forwardPorts": [3000],
+  "forwardPorts": [4321],
 
   "postCreateCommand": "pnpm install && cd /workspaces/astro && pnpm run build",
 
diff --git a/.devcontainer/with-nanostores/devcontainer.json b/.devcontainer/with-nanostores/devcontainer.json
index 5968f8a3d..656776b2a 100644
--- a/.devcontainer/with-nanostores/devcontainer.json
+++ b/.devcontainer/with-nanostores/devcontainer.json
@@ -7,13 +7,13 @@
   "workspaceFolder": "/workspaces/astro/examples/with-nanostores",
 
   "portsAttributes": {
-    "3000": {
+    "4321": {
       "label": "Application",
       "onAutoForward": "openPreview"
     }
   },
 
-  "forwardPorts": [3000],
+  "forwardPorts": [4321],
 
   "postCreateCommand": "pnpm install && cd /workspaces/astro && pnpm run build",
 
diff --git a/.devcontainer/with-tailwindcss/devcontainer.json b/.devcontainer/with-tailwindcss/devcontainer.json
index 73f2c7dfe..6e7298a6f 100644
--- a/.devcontainer/with-tailwindcss/devcontainer.json
+++ b/.devcontainer/with-tailwindcss/devcontainer.json
@@ -7,13 +7,13 @@
   "workspaceFolder": "/workspaces/astro/examples/with-tailwindcss",
 
   "portsAttributes": {
-    "3000": {
+    "4321": {
       "label": "Application",
       "onAutoForward": "openPreview"
     }
   },
 
-  "forwardPorts": [3000],
+  "forwardPorts": [4321],
 
   "postCreateCommand": "pnpm install && cd /workspaces/astro && pnpm run build",
 
diff --git a/.devcontainer/with-vite-plugin-pwa/devcontainer.json b/.devcontainer/with-vite-plugin-pwa/devcontainer.json
index 54d9a5c6a..d716cded0 100644
--- a/.devcontainer/with-vite-plugin-pwa/devcontainer.json
+++ b/.devcontainer/with-vite-plugin-pwa/devcontainer.json
@@ -7,13 +7,13 @@
   "workspaceFolder": "/workspaces/astro/examples/with-vite-plugin-pwa",
 
   "portsAttributes": {
-    "3000": {
+    "4321": {
       "label": "Application",
       "onAutoForward": "openPreview"
     }
   },
 
-  "forwardPorts": [3000],
+  "forwardPorts": [4321],
 
   "postCreateCommand": "pnpm install && cd /workspaces/astro && pnpm run build",
 
diff --git a/.devcontainer/with-vitest/devcontainer.json b/.devcontainer/with-vitest/devcontainer.json
index 079fa868e..793108939 100644
--- a/.devcontainer/with-vitest/devcontainer.json
+++ b/.devcontainer/with-vitest/devcontainer.json
@@ -7,13 +7,13 @@
   "workspaceFolder": "/workspaces/astro/examples/with-vitest",
 
   "portsAttributes": {
-    "3000": {
+    "4321": {
       "label": "Application",
       "onAutoForward": "openPreview"
     }
   },
 
-  "forwardPorts": [3000],
+  "forwardPorts": [4321],
 
   "postCreateCommand": "pnpm install && cd /workspaces/astro && pnpm run build",
 
diff --git a/.gitpod.yml b/.gitpod.yml
index 83205f4df..28e02e923 100644
--- a/.gitpod.yml
+++ b/.gitpod.yml
@@ -18,7 +18,7 @@ vscode:
     - esbenp.prettier-vscode
     - dbaeumer.vscode-eslint
 ports:
-  - port: 3000
+  - port: 4321
     onOpen: open-preview
 github:
   prebuilds:
diff --git a/examples/basics/README.md b/examples/basics/README.md
index 839455718..5369073b9 100644
--- a/examples/basics/README.md
+++ b/examples/basics/README.md
@@ -43,7 +43,7 @@ All commands are run from the root of the project, from a terminal:
 | Command                   | Action                                           |
 | :------------------------ | :----------------------------------------------- |
 | `npm install`             | Installs dependencies                            |
-| `npm run dev`             | Starts local dev server at `localhost:3000`      |
+| `npm run dev`             | Starts local dev server at `localhost:4321`      |
 | `npm run build`           | Build your production site to `./dist/`          |
 | `npm run preview`         | Preview your build locally, before deploying     |
 | `npm run astro ...`       | Run CLI commands like `astro add`, `astro check` |
diff --git a/examples/basics/sandbox.config.json b/examples/basics/sandbox.config.json
index 9178af77d..8e476b8cc 100644
--- a/examples/basics/sandbox.config.json
+++ b/examples/basics/sandbox.config.json
@@ -4,7 +4,7 @@
   "view": "browser",
   "template": "node",
   "container": {
-    "port": 3000,
+    "port": 4321,
     "startScript": "start",
     "node": "14"
   }
diff --git a/examples/blog/README.md b/examples/blog/README.md
index 11bc070ef..67d0cfc2e 100644
--- a/examples/blog/README.md
+++ b/examples/blog/README.md
@@ -53,7 +53,7 @@ All commands are run from the root of the project, from a terminal:
 | Command                   | Action                                           |
 | :------------------------ | :----------------------------------------------- |
 | `npm install`             | Installs dependencies                            |
-| `npm run dev`             | Starts local dev server at `localhost:3000`      |
+| `npm run dev`             | Starts local dev server at `localhost:4321`      |
 | `npm run build`           | Build your production site to `./dist/`          |
 | `npm run preview`         | Preview your build locally, before deploying     |
 | `npm run astro ...`       | Run CLI commands like `astro add`, `astro check` |
diff --git a/examples/blog/sandbox.config.json b/examples/blog/sandbox.config.json
index 9178af77d..8e476b8cc 100644
--- a/examples/blog/sandbox.config.json
+++ b/examples/blog/sandbox.config.json
@@ -4,7 +4,7 @@
   "view": "browser",
   "template": "node",
   "container": {
-    "port": 3000,
+    "port": 4321,
     "startScript": "start",
     "node": "14"
   }
diff --git a/examples/deno/README.md b/examples/deno/README.md
index 98f7ee020..af49ebcb7 100644
--- a/examples/deno/README.md
+++ b/examples/deno/README.md
@@ -42,7 +42,7 @@ All commands are run from the root of the project, from a terminal:
 | Command                   | Action                                           |
 | :------------------------ | :----------------------------------------------- |
 | `npm install`             | Installs dependencies                            |
-| `npm run dev`             | Starts local dev server at `localhost:3000`      |
+| `npm run dev`             | Starts local dev server at `localhost:4321`      |
 | `npm run build`           | Build your production site to `./dist/`          |
 | `npm run preview`         | Preview your build locally, before deploying     |
 |                           | (preview uses Deno CLI)                          |
diff --git a/examples/deno/sandbox.config.json b/examples/deno/sandbox.config.json
index 9178af77d..8e476b8cc 100644
--- a/examples/deno/sandbox.config.json
+++ b/examples/deno/sandbox.config.json
@@ -4,7 +4,7 @@
   "view": "browser",
   "template": "node",
   "container": {
-    "port": 3000,
+    "port": 4321,
     "startScript": "start",
     "node": "14"
   }
diff --git a/examples/framework-alpine/sandbox.config.json b/examples/framework-alpine/sandbox.config.json
index 9178af77d..8e476b8cc 100644
--- a/examples/framework-alpine/sandbox.config.json
+++ b/examples/framework-alpine/sandbox.config.json
@@ -4,7 +4,7 @@
   "view": "browser",
   "template": "node",
   "container": {
-    "port": 3000,
+    "port": 4321,
     "startScript": "start",
     "node": "14"
   }
diff --git a/examples/framework-lit/sandbox.config.json b/examples/framework-lit/sandbox.config.json
index 9178af77d..8e476b8cc 100644
--- a/examples/framework-lit/sandbox.config.json
+++ b/examples/framework-lit/sandbox.config.json
@@ -4,7 +4,7 @@
   "view": "browser",
   "template": "node",
   "container": {
-    "port": 3000,
+    "port": 4321,
     "startScript": "start",
     "node": "14"
   }
diff --git a/examples/framework-multiple/sandbox.config.json b/examples/framework-multiple/sandbox.config.json
index 9178af77d..8e476b8cc 100644
--- a/examples/framework-multiple/sandbox.config.json
+++ b/examples/framework-multiple/sandbox.config.json
@@ -4,7 +4,7 @@
   "view": "browser",
   "template": "node",
   "container": {
-    "port": 3000,
+    "port": 4321,
     "startScript": "start",
     "node": "14"
   }
diff --git a/examples/framework-preact/sandbox.config.json b/examples/framework-preact/sandbox.config.json
index 9178af77d..8e476b8cc 100644
--- a/examples/framework-preact/sandbox.config.json
+++ b/examples/framework-preact/sandbox.config.json
@@ -4,7 +4,7 @@
   "view": "browser",
   "template": "node",
   "container": {
-    "port": 3000,
+    "port": 4321,
     "startScript": "start",
     "node": "14"
   }
diff --git a/examples/framework-react/sandbox.config.json b/examples/framework-react/sandbox.config.json
index 9178af77d..8e476b8cc 100644
--- a/examples/framework-react/sandbox.config.json
+++ b/examples/framework-react/sandbox.config.json
@@ -4,7 +4,7 @@
   "view": "browser",
   "template": "node",
   "container": {
-    "port": 3000,
+    "port": 4321,
     "startScript": "start",
     "node": "14"
   }
diff --git a/examples/framework-solid/sandbox.config.json b/examples/framework-solid/sandbox.config.json
index 9178af77d..8e476b8cc 100644
--- a/examples/framework-solid/sandbox.config.json
+++ b/examples/framework-solid/sandbox.config.json
@@ -4,7 +4,7 @@
   "view": "browser",
   "template": "node",
   "container": {
-    "port": 3000,
+    "port": 4321,
     "startScript": "start",
     "node": "14"
   }
diff --git a/examples/framework-svelte/sandbox.config.json b/examples/framework-svelte/sandbox.config.json
index 9178af77d..8e476b8cc 100644
--- a/examples/framework-svelte/sandbox.config.json
+++ b/examples/framework-svelte/sandbox.config.json
@@ -4,7 +4,7 @@
   "view": "browser",
   "template": "node",
   "container": {
-    "port": 3000,
+    "port": 4321,
     "startScript": "start",
     "node": "14"
   }
diff --git a/examples/framework-vue/sandbox.config.json b/examples/framework-vue/sandbox.config.json
index 9178af77d..8e476b8cc 100644
--- a/examples/framework-vue/sandbox.config.json
+++ b/examples/framework-vue/sandbox.config.json
@@ -4,7 +4,7 @@
   "view": "browser",
   "template": "node",
   "container": {
-    "port": 3000,
+    "port": 4321,
     "startScript": "start",
     "node": "14"
   }
diff --git a/examples/hackernews/README.md b/examples/hackernews/README.md
index 937ad23ea..042a7807b 100644
--- a/examples/hackernews/README.md
+++ b/examples/hackernews/README.md
@@ -48,7 +48,7 @@ All commands are run from the root of the project, from a terminal:
 | Command                   | Action                                           |
 | :------------------------ | :----------------------------------------------- |
 | `npm install`             | Installs dependencies                            |
-| `npm run dev`             | Starts local dev server at `localhost:3000`      |
+| `npm run dev`             | Starts local dev server at `localhost:4321`      |
 | `npm run build`           | Build your production site to `./dist/`          |
 | `npm run preview`         | Preview your build locally, before deploying     |
 | `npm run astro ...`       | Run CLI commands like `astro add`, `astro check` |
diff --git a/examples/hackernews/sandbox.config.json b/examples/hackernews/sandbox.config.json
index 9178af77d..8e476b8cc 100644
--- a/examples/hackernews/sandbox.config.json
+++ b/examples/hackernews/sandbox.config.json
@@ -4,7 +4,7 @@
   "view": "browser",
   "template": "node",
   "container": {
-    "port": 3000,
+    "port": 4321,
     "startScript": "start",
     "node": "14"
   }
diff --git a/examples/minimal/README.md b/examples/minimal/README.md
index 3c261d317..20bad6615 100644
--- a/examples/minimal/README.md
+++ b/examples/minimal/README.md
@@ -36,7 +36,7 @@ All commands are run from the root of the project, from a terminal:
 | Command                   | Action                                           |
 | :------------------------ | :----------------------------------------------- |
 | `npm install`             | Installs dependencies                            |
-| `npm run dev`             | Starts local dev server at `localhost:3000`      |
+| `npm run dev`             | Starts local dev server at `localhost:4321`      |
 | `npm run build`           | Build your production site to `./dist/`          |
 | `npm run preview`         | Preview your build locally, before deploying     |
 | `npm run astro ...`       | Run CLI commands like `astro add`, `astro check` |
diff --git a/examples/minimal/sandbox.config.json b/examples/minimal/sandbox.config.json
index 9178af77d..8e476b8cc 100644
--- a/examples/minimal/sandbox.config.json
+++ b/examples/minimal/sandbox.config.json
@@ -4,7 +4,7 @@
   "view": "browser",
   "template": "node",
   "container": {
-    "port": 3000,
+    "port": 4321,
     "startScript": "start",
     "node": "14"
   }
diff --git a/examples/non-html-pages/README.md b/examples/non-html-pages/README.md
index d1caeed41..ecdee84b1 100644
--- a/examples/non-html-pages/README.md
+++ b/examples/non-html-pages/README.md
@@ -41,7 +41,7 @@ All commands are run from the root of the project, from a terminal:
 | Command                   | Action                                           |
 | :------------------------ | :----------------------------------------------- |
 | `npm install`             | Installs dependencies                            |
-| `npm run dev`             | Starts local dev server at `localhost:3000`      |
+| `npm run dev`             | Starts local dev server at `localhost:4321`      |
 | `npm run build`           | Build your production site to `./dist/`          |
 | `npm run preview`         | Preview your build locally, before deploying     |
 | `npm run astro ...`       | Run CLI commands like `astro add`, `astro check` |
diff --git a/examples/non-html-pages/sandbox.config.json b/examples/non-html-pages/sandbox.config.json
index 9178af77d..8e476b8cc 100644
--- a/examples/non-html-pages/sandbox.config.json
+++ b/examples/non-html-pages/sandbox.config.json
@@ -4,7 +4,7 @@
   "view": "browser",
   "template": "node",
   "container": {
-    "port": 3000,
+    "port": 4321,
     "startScript": "start",
     "node": "14"
   }
diff --git a/examples/portfolio/README.md b/examples/portfolio/README.md
index 7ca90501a..3c8ee3aa4 100644
--- a/examples/portfolio/README.md
+++ b/examples/portfolio/README.md
@@ -19,7 +19,7 @@ All commands are run from the root of the project, from a terminal:
 | Command                   | Action                                           |
 | :------------------------ | :----------------------------------------------- |
 | `npm install`             | Installs dependencies                            |
-| `npm run dev`             | Starts local dev server at `localhost:3000`      |
+| `npm run dev`             | Starts local dev server at `localhost:4321`      |
 | `npm run build`           | Build your production site to `./dist/`          |
 | `npm run preview`         | Preview your build locally, before deploying     |
 | `npm run astro ...`       | Run CLI commands like `astro add`, `astro check` |
diff --git a/examples/portfolio/sandbox.config.json b/examples/portfolio/sandbox.config.json
index 9178af77d..8e476b8cc 100644
--- a/examples/portfolio/sandbox.config.json
+++ b/examples/portfolio/sandbox.config.json
@@ -4,7 +4,7 @@
   "view": "browser",
   "template": "node",
   "container": {
-    "port": 3000,
+    "port": 4321,
     "startScript": "start",
     "node": "14"
   }
diff --git a/examples/with-markdoc/README.md b/examples/with-markdoc/README.md
index 4f44648da..1a1acc1a5 100644
--- a/examples/with-markdoc/README.md
+++ b/examples/with-markdoc/README.md
@@ -45,7 +45,7 @@ All commands are run from the root of the project, from a terminal:
 | Command                   | Action                                           |
 | :------------------------ | :----------------------------------------------- |
 | `npm install`             | Installs dependencies                            |
-| `npm run dev`             | Starts local dev server at `localhost:3000`      |
+| `npm run dev`             | Starts local dev server at `localhost:4321`      |
 | `npm run build`           | Build your production site to `./dist/`          |
 | `npm run preview`         | Preview your build locally, before deploying     |
 | `npm run astro ...`       | Run CLI commands like `astro add`, `astro check` |
diff --git a/examples/with-markdoc/sandbox.config.json b/examples/with-markdoc/sandbox.config.json
index 9178af77d..8e476b8cc 100644
--- a/examples/with-markdoc/sandbox.config.json
+++ b/examples/with-markdoc/sandbox.config.json
@@ -4,7 +4,7 @@
   "view": "browser",
   "template": "node",
   "container": {
-    "port": 3000,
+    "port": 4321,
     "startScript": "start",
     "node": "14"
   }
diff --git a/examples/with-markdown-plugins/sandbox.config.json b/examples/with-markdown-plugins/sandbox.config.json
index 9178af77d..8e476b8cc 100644
--- a/examples/with-markdown-plugins/sandbox.config.json
+++ b/examples/with-markdown-plugins/sandbox.config.json
@@ -4,7 +4,7 @@
   "view": "browser",
   "template": "node",
   "container": {
-    "port": 3000,
+    "port": 4321,
     "startScript": "start",
     "node": "14"
   }
diff --git a/examples/with-markdown-shiki/sandbox.config.json b/examples/with-markdown-shiki/sandbox.config.json
index 9178af77d..8e476b8cc 100644
--- a/examples/with-markdown-shiki/sandbox.config.json
+++ b/examples/with-markdown-shiki/sandbox.config.json
@@ -4,7 +4,7 @@
   "view": "browser",
   "template": "node",
   "container": {
-    "port": 3000,
+    "port": 4321,
     "startScript": "start",
     "node": "14"
   }
diff --git a/examples/with-mdx/sandbox.config.json b/examples/with-mdx/sandbox.config.json
index 9178af77d..8e476b8cc 100644
--- a/examples/with-mdx/sandbox.config.json
+++ b/examples/with-mdx/sandbox.config.json
@@ -4,7 +4,7 @@
   "view": "browser",
   "template": "node",
   "container": {
-    "port": 3000,
+    "port": 4321,
     "startScript": "start",
     "node": "14"
   }
diff --git a/examples/with-nanostores/sandbox.config.json b/examples/with-nanostores/sandbox.config.json
index 9178af77d..8e476b8cc 100644
--- a/examples/with-nanostores/sandbox.config.json
+++ b/examples/with-nanostores/sandbox.config.json
@@ -4,7 +4,7 @@
   "view": "browser",
   "template": "node",
   "container": {
-    "port": 3000,
+    "port": 4321,
     "startScript": "start",
     "node": "14"
   }
diff --git a/examples/with-tailwindcss/sandbox.config.json b/examples/with-tailwindcss/sandbox.config.json
index 9178af77d..8e476b8cc 100644
--- a/examples/with-tailwindcss/sandbox.config.json
+++ b/examples/with-tailwindcss/sandbox.config.json
@@ -4,7 +4,7 @@
   "view": "browser",
   "template": "node",
   "container": {
-    "port": 3000,
+    "port": 4321,
     "startScript": "start",
     "node": "14"
   }
diff --git a/examples/with-vite-plugin-pwa/README.md b/examples/with-vite-plugin-pwa/README.md
index 9c29863db..555d3e7de 100644
--- a/examples/with-vite-plugin-pwa/README.md
+++ b/examples/with-vite-plugin-pwa/README.md
@@ -36,7 +36,7 @@ All commands are run from the root of the project, from a terminal:
 | Command                   | Action                                           |
 | :------------------------ | :----------------------------------------------- |
 | `npm install`             | Installs dependencies                            |
-| `npm run dev`             | Starts local dev server at `localhost:3000`      |
+| `npm run dev`             | Starts local dev server at `localhost:4321`      |
 | `npm run build`           | Build your production site to `./dist/`          |
 | `npm run preview`         | Preview your build locally, before deploying     |
 | `npm run astro ...`       | Run CLI commands like `astro add`, `astro check` |
diff --git a/examples/with-vite-plugin-pwa/sandbox.config.json b/examples/with-vite-plugin-pwa/sandbox.config.json
index 9178af77d..8e476b8cc 100644
--- a/examples/with-vite-plugin-pwa/sandbox.config.json
+++ b/examples/with-vite-plugin-pwa/sandbox.config.json
@@ -4,7 +4,7 @@
   "view": "browser",
   "template": "node",
   "container": {
-    "port": 3000,
+    "port": 4321,
     "startScript": "start",
     "node": "14"
   }
diff --git a/examples/with-vitest/sandbox.config.json b/examples/with-vitest/sandbox.config.json
index 9178af77d..8e476b8cc 100644
--- a/examples/with-vitest/sandbox.config.json
+++ b/examples/with-vitest/sandbox.config.json
@@ -4,7 +4,7 @@
   "view": "browser",
   "template": "node",
   "container": {
-    "port": 3000,
+    "port": 4321,
     "startScript": "start",
     "node": "14"
   }
diff --git a/packages/astro/src/@types/astro.ts b/packages/astro/src/@types/astro.ts
index dc710ec2f..1e5863d12 100644
--- a/packages/astro/src/@types/astro.ts
+++ b/packages/astro/src/@types/astro.ts
@@ -327,7 +327,7 @@ type ServerConfig = {
 	/**
 	 * @name server.port
 	 * @type {number}
-	 * @default `3000`
+	 * @default `4321`
 	 * @description
 	 * Set which port the dev server should listen on.
 	 *
@@ -915,7 +915,7 @@ export interface AstroUserConfig {
 	 * ```js
 	 * {
 	 *   // Example: Use the function syntax to customize based on command
-	 *   server: ({ command }) => ({ port: command === 'dev' ? 3000 : 4000 })
+	 *   server: ({ command }) => ({ port: command === 'dev' ? 4321 : 4000 })
 	 * }
 	 * ```
 	 */
@@ -937,7 +937,7 @@ export interface AstroUserConfig {
 	 * @docs
 	 * @name server.port
 	 * @type {number}
-	 * @default `3000`
+	 * @default `4321`
 	 * @description
 	 * Set which port the server should listen on.
 	 *
diff --git a/packages/astro/src/cli/dev/index.ts b/packages/astro/src/cli/dev/index.ts
index e55496c4a..5db47fb97 100644
--- a/packages/astro/src/cli/dev/index.ts
+++ b/packages/astro/src/cli/dev/index.ts
@@ -15,7 +15,7 @@ export async function dev({ flags }: DevOptions) {
 			usage: '[...flags]',
 			tables: {
 				Flags: [
-					['--port', `Specify which port to run on. Defaults to 3000.`],
+					['--port', `Specify which port to run on. Defaults to 4321.`],
 					['--host', `Listen on all addresses, including LAN and public addresses.`],
 					['--host <custom-address>', `Expose on a network IP address at <custom-address>`],
 					['--open', 'Automatically open the app in the browser on server start'],
diff --git a/packages/astro/src/core/config/schema.ts b/packages/astro/src/core/config/schema.ts
index c57f8b95a..c40953187 100644
--- a/packages/astro/src/core/config/schema.ts
+++ b/packages/astro/src/core/config/schema.ts
@@ -32,7 +32,7 @@ const ASTRO_CONFIG_DEFAULTS = {
 	compressHTML: false,
 	server: {
 		host: false,
-		port: 3000,
+		port: 4321,
 		open: false,
 	},
 	integrations: [],
diff --git a/packages/astro/test/cli.test.js b/packages/astro/test/cli.test.js
index 7626cc495..82cf7a12d 100644
--- a/packages/astro/test/cli.test.js
+++ b/packages/astro/test/cli.test.js
@@ -131,8 +131,8 @@ describe('astro cli', () => {
 
 				// Note: our tests run in parallel so this could be 3000+!
 				expect(Number.parseInt(localURL.port)).to.be.greaterThanOrEqual(
-					3000,
-					`Expected Port to be >= 3000`
+					4321,
+					`Expected Port to be >= 4321`
 				);
 				expect(networkURL.port).to.be.equal(
 					localURL.port,
diff --git a/packages/astro/test/fixtures/astro-basic/astro.config.mjs b/packages/astro/test/fixtures/astro-basic/astro.config.mjs
index b7b7dafe6..1b2eb163d 100644
--- a/packages/astro/test/fixtures/astro-basic/astro.config.mjs
+++ b/packages/astro/test/fixtures/astro-basic/astro.config.mjs
@@ -5,5 +5,5 @@ import preact from '@astrojs/preact';
 export default defineConfig({
 	integrations: [preact()],
 	// make sure CLI flags have precedence
-  server: () => ({ port: 3000 })
+  server: () => ({ port: 4321 })
 });
diff --git a/packages/astro/test/fixtures/ssr-preview/preview.mjs b/packages/astro/test/fixtures/ssr-preview/preview.mjs
index 745f22624..d8d57afa8 100644
--- a/packages/astro/test/fixtures/ssr-preview/preview.mjs
+++ b/packages/astro/test/fixtures/ssr-preview/preview.mjs
@@ -1,7 +1,7 @@
 export default () => {
 	// noop
 	return {
-		port: 3000,
+		port: 4321,
 		closed() {},
 		stop() {}
 	}
diff --git a/packages/integrations/image/test/fixtures/background-color-image/astro.config.mjs b/packages/integrations/image/test/fixtures/background-color-image/astro.config.mjs
index f00c6ebae..f2b44a4a0 100644
--- a/packages/integrations/image/test/fixtures/background-color-image/astro.config.mjs
+++ b/packages/integrations/image/test/fixtures/background-color-image/astro.config.mjs
@@ -3,6 +3,6 @@ import image from '@astrojs/image';
 
 // https://astro.build/config
 export default defineConfig({
-	site: 'http://localhost:3000',
+	site: 'http://localhost:4321',
 	integrations: [image({ logLevel: 'silent', serviceEntryPoint: '@astrojs/image/sharp' })]
 });
diff --git a/packages/integrations/image/test/fixtures/basic-image/astro.config.mjs b/packages/integrations/image/test/fixtures/basic-image/astro.config.mjs
index f00c6ebae..f2b44a4a0 100644
--- a/packages/integrations/image/test/fixtures/basic-image/astro.config.mjs
+++ b/packages/integrations/image/test/fixtures/basic-image/astro.config.mjs
@@ -3,6 +3,6 @@ import image from '@astrojs/image';
 
 // https://astro.build/config
 export default defineConfig({
-	site: 'http://localhost:3000',
+	site: 'http://localhost:4321',
 	integrations: [image({ logLevel: 'silent', serviceEntryPoint: '@astrojs/image/sharp' })]
 });
diff --git a/packages/integrations/image/test/fixtures/basic-picture/astro.config.mjs b/packages/integrations/image/test/fixtures/basic-picture/astro.config.mjs
index f00c6ebae..f2b44a4a0 100644
--- a/packages/integrations/image/test/fixtures/basic-picture/astro.config.mjs
+++ b/packages/integrations/image/test/fixtures/basic-picture/astro.config.mjs
@@ -3,6 +3,6 @@ import image from '@astrojs/image';
 
 // https://astro.build/config
 export default defineConfig({
-	site: 'http://localhost:3000',
+	site: 'http://localhost:4321',
 	integrations: [image({ logLevel: 'silent', serviceEntryPoint: '@astrojs/image/sharp' })]
 });
diff --git a/packages/integrations/image/test/fixtures/get-image-remote/astro.config.mjs b/packages/integrations/image/test/fixtures/get-image-remote/astro.config.mjs
index f00c6ebae..f2b44a4a0 100644
--- a/packages/integrations/image/test/fixtures/get-image-remote/astro.config.mjs
+++ b/packages/integrations/image/test/fixtures/get-image-remote/astro.config.mjs
@@ -3,6 +3,6 @@ import image from '@astrojs/image';
 
 // https://astro.build/config
 export default defineConfig({
-	site: 'http://localhost:3000',
+	site: 'http://localhost:4321',
 	integrations: [image({ logLevel: 'silent', serviceEntryPoint: '@astrojs/image/sharp' })]
 });
diff --git a/packages/integrations/image/test/fixtures/no-alt-text-image/astro.config.mjs b/packages/integrations/image/test/fixtures/no-alt-text-image/astro.config.mjs
index f00c6ebae..f2b44a4a0 100644
--- a/packages/integrations/image/test/fixtures/no-alt-text-image/astro.config.mjs
+++ b/packages/integrations/image/test/fixtures/no-alt-text-image/astro.config.mjs
@@ -3,6 +3,6 @@ import image from '@astrojs/image';
 
 // https://astro.build/config
 export default defineConfig({
-	site: 'http://localhost:3000',
+	site: 'http://localhost:4321',
 	integrations: [image({ logLevel: 'silent', serviceEntryPoint: '@astrojs/image/sharp' })]
 });
diff --git a/packages/integrations/image/test/fixtures/no-alt-text-picture/astro.config.mjs b/packages/integrations/image/test/fixtures/no-alt-text-picture/astro.config.mjs
index f00c6ebae..f2b44a4a0 100644
--- a/packages/integrations/image/test/fixtures/no-alt-text-picture/astro.config.mjs
+++ b/packages/integrations/image/test/fixtures/no-alt-text-picture/astro.config.mjs
@@ -3,6 +3,6 @@ import image from '@astrojs/image';
 
 // https://astro.build/config
 export default defineConfig({
-	site: 'http://localhost:3000',
+	site: 'http://localhost:4321',
 	integrations: [image({ logLevel: 'silent', serviceEntryPoint: '@astrojs/image/sharp' })]
 });
diff --git a/packages/integrations/image/test/fixtures/rotation/astro.config.mjs b/packages/integrations/image/test/fixtures/rotation/astro.config.mjs
index f00c6ebae..f2b44a4a0 100644
--- a/packages/integrations/image/test/fixtures/rotation/astro.config.mjs
+++ b/packages/integrations/image/test/fixtures/rotation/astro.config.mjs
@@ -3,6 +3,6 @@ import image from '@astrojs/image';
 
 // https://astro.build/config
 export default defineConfig({
-	site: 'http://localhost:3000',
+	site: 'http://localhost:4321',
 	integrations: [image({ logLevel: 'silent', serviceEntryPoint: '@astrojs/image/sharp' })]
 });
diff --git a/packages/integrations/image/test/fixtures/squoosh-service/astro.config.mjs b/packages/integrations/image/test/fixtures/squoosh-service/astro.config.mjs
index 7dafac3b6..fcbb8ec5e 100644
--- a/packages/integrations/image/test/fixtures/squoosh-service/astro.config.mjs
+++ b/packages/integrations/image/test/fixtures/squoosh-service/astro.config.mjs
@@ -3,6 +3,6 @@ import image from '@astrojs/image';
 
 // https://astro.build/config
 export default defineConfig({
-	site: 'http://localhost:3000',
+	site: 'http://localhost:4321',
 	integrations: [image({ logLevel: 'silent' })]
 });
diff --git a/packages/integrations/image/test/fixtures/with-mdx/astro.config.mjs b/packages/integrations/image/test/fixtures/with-mdx/astro.config.mjs
index 7989a6f57..3aae5b3a2 100644
--- a/packages/integrations/image/test/fixtures/with-mdx/astro.config.mjs
+++ b/packages/integrations/image/test/fixtures/with-mdx/astro.config.mjs
@@ -4,6 +4,6 @@ import mdx from '@astrojs/mdx';
 
 // https://astro.build/config
 export default defineConfig({
-	site: 'http://localhost:3000',
+	site: 'http://localhost:4321',
 	integrations: [image({ logLevel: 'silent', serviceEntryPoint: '@astrojs/image/sharp' }), mdx()]
 });
diff --git a/packages/integrations/node/README.md b/packages/integrations/node/README.md
index e97544956..5d3642be6 100644
--- a/packages/integrations/node/README.md
+++ b/packages/integrations/node/README.md
@@ -159,7 +159,7 @@ For standalone mode the server handles file servering in addition to the page an
 You can override the host and port the standalone server runs on by passing them as environment variables at runtime:
 
 ```shell
-HOST=0.0.0.0 PORT=3000 node ./dist/server/entry.mjs
+HOST=0.0.0.0 PORT=4321 node ./dist/server/entry.mjs
 ```
 
 #### HTTPS
diff --git a/packages/integrations/prefetch/playwright.config.js b/packages/integrations/prefetch/playwright.config.js
index d9600393e..7fb92ae0c 100644
--- a/packages/integrations/prefetch/playwright.config.js
+++ b/packages/integrations/prefetch/playwright.config.js
@@ -25,7 +25,7 @@ const config = {
 		/* Maximum time each action such as `click()` can take. Defaults to 0 (no limit). */
 		actionTimeout: 0,
 		/* Base URL to use in actions like `await page.goto('/')`. */
-		baseURL: process.env.PLAYWRIGHT_TEST_BASE_URL || 'http://localhost:3000',
+		baseURL: process.env.PLAYWRIGHT_TEST_BASE_URL || 'http://localhost:4321',
 
 		/* Collect trace when retrying the failed test. See https://playwright.dev/docs/trace-viewer */
 		trace: 'on-first-retry',