diff --git a/packages/vite/rollupLicensePlugin.ts b/packages/vite/rollupLicensePlugin.ts
index d3dce56a7..aa08c64f2 100644
--- a/packages/vite/rollupLicensePlugin.ts
+++ b/packages/vite/rollupLicensePlugin.ts
@@ -88,7 +88,7 @@ export default function licensePlugin(
         `${sortLicenses(licenses).join(', ')}\n\n` +
         `# Bundled dependencies:\n` +
         dependencyLicenseTexts
-      const existingLicenseText = fs.readFileSync(licenseFilePath, 'utf8')
+      const existingLicenseText = fs.readFileSync(licenseFilePath, 'utf-8')
       if (existingLicenseText !== licenseText) {
         fs.writeFileSync(licenseFilePath, licenseText)
         console.warn(
diff --git a/packages/vite/src/node/config.ts b/packages/vite/src/node/config.ts
index 83a5e4556..178e73b81 100644
--- a/packages/vite/src/node/config.ts
+++ b/packages/vite/src/node/config.ts
@@ -1174,7 +1174,7 @@ async function bundleConfigFile(
         name: 'inject-file-scope-variables',
         setup(build) {
           build.onLoad({ filter: /\.[cm]?[jt]s$/ }, async (args) => {
-            const contents = await fsp.readFile(args.path, 'utf8')
+            const contents = await fsp.readFile(args.path, 'utf-8')
             const injectValues =
               `const ${dirnameVarName} = ${JSON.stringify(
                 path.dirname(args.path),
diff --git a/playground/csp/vite.config.js b/playground/csp/vite.config.js
index 08d2b74f9..84d6d92ba 100644
--- a/playground/csp/vite.config.js
+++ b/playground/csp/vite.config.js
@@ -28,7 +28,7 @@ const setNonceHeader = (res, nonce) => {
 const createMiddleware = (file, transform) => async (req, res) => {
   const nonce = createNonce()
   setNonceHeader(res, nonce)
-  const content = await fs.readFile(path.join(__dirname, file), 'utf8')
+  const content = await fs.readFile(path.join(__dirname, file), 'utf-8')
   const transformedContent = await transform(content, req.originalUrl)
   res.setHeader('Content-Type', 'text/html')
   res.end(transformedContent.replaceAll(noncePlaceholder, nonce))
diff --git a/playground/json/server.js b/playground/json/server.js
index 982b7dcc0..fea792d4e 100644
--- a/playground/json/server.js
+++ b/playground/json/server.js
@@ -69,7 +69,7 @@ export async function createServer(root = process.cwd(), hmrPort) {
       }
 
       const htmlLoc = resolve(`.${url}`)
-      let html = fs.readFileSync(htmlLoc, 'utf8')
+      let html = fs.readFileSync(htmlLoc, 'utf-8')
       html = await vite.transformIndexHtml(url, html)
 
       res.status(200).set({ 'Content-Type': 'text/html' }).end(html)
diff --git a/playground/resolve-config/__tests__/resolve-config.spec.ts b/playground/resolve-config/__tests__/resolve-config.spec.ts
index eeb4f2c79..12f00aa16 100644
--- a/playground/resolve-config/__tests__/resolve-config.spec.ts
+++ b/playground/resolve-config/__tests__/resolve-config.spec.ts
@@ -13,7 +13,7 @@ const build = (configName: string) => {
 const getDistFile = (configName: string, extension: string) => {
   return fs.readFileSync(
     fromTestDir(`${configName}/dist/index.${extension}`),
-    'utf8',
+    'utf-8',
   )
 }
 
diff --git a/playground/resolve-config/__tests__/serve.ts b/playground/resolve-config/__tests__/serve.ts
index 39e84860c..76172577f 100644
--- a/playground/resolve-config/__tests__/serve.ts
+++ b/playground/resolve-config/__tests__/serve.ts
@@ -21,7 +21,7 @@ export async function serve() {
     await fs.rename(fromTestDir(configName, 'vite.config.ts'), pathToConf)
 
     if (['cjs', 'cts'].includes(configName)) {
-      const conf = await fs.readFile(pathToConf, 'utf8')
+      const conf = await fs.readFile(pathToConf, 'utf-8')
       await fs.writeFile(
         pathToConf,
         conf.replace('export default', 'module.exports = '),
@@ -30,7 +30,7 @@ export async function serve() {
 
     // Remove TS annotation for plain JavaScript file.
     if (configName.endsWith('js')) {
-      const conf = await fs.readFile(pathToConf, 'utf8')
+      const conf = await fs.readFile(pathToConf, 'utf-8')
       await fs.writeFile(pathToConf, conf.replace(': boolean', ''))
     }