diff --git a/.github/workflows/format.yml b/.github/workflows/format.yml
new file mode 100644
index 0000000..2783902
--- /dev/null
+++ b/.github/workflows/format.yml
@@ -0,0 +1,24 @@
+name: Node.js CI (format)
+
+on:
+    push:
+        branches: [main]
+    pull_request:
+        branches: [main]
+
+jobs:
+    format:
+        runs-on: ubuntu-latest
+
+        strategy:
+            matrix:
+                node-version: [21.x]
+
+        steps:
+            - uses: actions/checkout@v4
+            - name: Use Node.js ${{ matrix.node-version }}
+              uses: actions/setup-node@v4
+              with:
+                  node-version: ${{ matrix.node-version }}
+            - run: npm ci
+            - run: npm run format:check
diff --git a/.prettierrc.json b/.prettierrc.json
new file mode 100644
index 0000000..974b6c7
--- /dev/null
+++ b/.prettierrc.json
@@ -0,0 +1,5 @@
+{
+    "printWidth": 120,
+    "tabWidth": 4,
+    "trailingComma": "none"
+}
\ No newline at end of file
diff --git a/package-lock.json b/package-lock.json
index 1e56353..9f7e37b 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -11,6 +11,7 @@
       "dependencies": {
         "chokidar": "^3.6.0",
         "copy-webpack-plugin": "^12.0.2",
+        "prettier": "^3.2.5",
         "ts-loader": "^9.5.1",
         "ts-node": "^10.9.2",
         "twi-ext": "^0.4.1",
@@ -4709,6 +4710,20 @@
         "node": ">= 0.8.0"
       }
     },
+    "node_modules/prettier": {
+      "version": "3.2.5",
+      "resolved": "https://registry.npmjs.org/prettier/-/prettier-3.2.5.tgz",
+      "integrity": "sha512-3/GWa9aOC0YeD7LUfvOG2NiDyhOWRvt1k+rcKhOuYnMY24iiCphgneUfJDyFXd6rZCAnuLBv6UeAULtrhT/F4A==",
+      "bin": {
+        "prettier": "bin/prettier.cjs"
+      },
+      "engines": {
+        "node": ">=14"
+      },
+      "funding": {
+        "url": "https://github.com/prettier/prettier?sponsor=1"
+      }
+    },
     "node_modules/process": {
       "version": "0.11.10",
       "resolved": "https://registry.npmjs.org/process/-/process-0.11.10.tgz",
@@ -10071,6 +10086,11 @@
       "resolved": "https://registry.npmjs.org/prelude-ls/-/prelude-ls-1.2.1.tgz",
       "integrity": "sha512-vkcDPrRZo1QZLbn5RLGPpg/WmIQ65qoWWhcGKf/b5eplkkarX0m9z8ppCat4mlOqUsWpyNuYgO3VRyrYHSzX5g=="
     },
+    "prettier": {
+      "version": "3.2.5",
+      "resolved": "https://registry.npmjs.org/prettier/-/prettier-3.2.5.tgz",
+      "integrity": "sha512-3/GWa9aOC0YeD7LUfvOG2NiDyhOWRvt1k+rcKhOuYnMY24iiCphgneUfJDyFXd6rZCAnuLBv6UeAULtrhT/F4A=="
+    },
     "process": {
       "version": "0.11.10",
       "resolved": "https://registry.npmjs.org/process/-/process-0.11.10.tgz",
diff --git a/package.json b/package.json
index 212c475..b42f420 100644
--- a/package.json
+++ b/package.json
@@ -6,6 +6,8 @@
   "scripts": {
     "build": "webpack",
     "watch": "webpack --watch",
+    "format": "npx prettier --write ./src/**/*",
+    "format:check": "npx prettier --check ./src/**/*",
     "package": "ts-node ./script/package.ts",
     "version": "npm run build && git add ."
   },
@@ -27,6 +29,7 @@
   "dependencies": {
     "chokidar": "^3.6.0",
     "copy-webpack-plugin": "^12.0.2",
+    "prettier": "^3.2.5",
     "ts-loader": "^9.5.1",
     "ts-node": "^10.9.2",
     "twi-ext": "^0.4.1",
@@ -35,4 +38,4 @@
     "webpack": "^5.91.0",
     "webpack-cli": "^5.1.4"
   }
-}
+}
\ No newline at end of file
diff --git a/src/_locales/en/messages.json b/src/_locales/en/messages.json
index a525962..e1520fa 100644
--- a/src/_locales/en/messages.json
+++ b/src/_locales/en/messages.json
@@ -2,4 +2,4 @@
     "manifest_description": {
         "message": "This extension hides the number of impressions on Twitter and prevents the creation of an approval desire monster."
     }
-}
\ No newline at end of file
+}
diff --git a/src/_locales/ja/messages.json b/src/_locales/ja/messages.json
index be80edb..85da80e 100644
--- a/src/_locales/ja/messages.json
+++ b/src/_locales/ja/messages.json
@@ -2,4 +2,4 @@
     "manifest_description": {
         "message": "Twitterのインプレッション数を非表示にして、承認欲求モンスターが生まれてしまうのを防ぐ拡張機能です。"
     }
-}
\ No newline at end of file
+}
diff --git a/src/manifest/v2.json b/src/manifest/v2.json
index ea636f2..d758c30 100644
--- a/src/manifest/v2.json
+++ b/src/manifest/v2.json
@@ -11,18 +11,12 @@
     },
     "content_scripts": [
         {
-            "matches": [
-                "https://twitter.com/*",
-                "https://mobile.twitter.com/*",
-                "https://pro.twitter.com/*"
-            ],
-            "js": [
-                "js/index.js"
-            ]
+            "matches": ["https://twitter.com/*", "https://mobile.twitter.com/*", "https://pro.twitter.com/*"],
+            "js": ["js/index.js"]
         }
     ],
     "default_locale": "en",
     "browser_specific_settings": {
         "gecko_android": {}
     }
-}
\ No newline at end of file
+}
diff --git a/src/manifest/v3.json b/src/manifest/v3.json
index ebc6104..e0cc825 100644
--- a/src/manifest/v3.json
+++ b/src/manifest/v3.json
@@ -11,18 +11,12 @@
     },
     "content_scripts": [
         {
-            "matches": [
-                "https://twitter.com/*",
-                "https://mobile.twitter.com/*",
-                "https://pro.twitter.com/*"
-            ],
-            "js": [
-                "js/index.js"
-            ]
+            "matches": ["https://twitter.com/*", "https://mobile.twitter.com/*", "https://pro.twitter.com/*"],
+            "js": ["js/index.js"]
         }
     ],
     "default_locale": "en",
     "browser_specific_settings": {
         "gecko_android": {}
     }
-}
\ No newline at end of file
+}