diff --git a/packages/vite/src/node/build.ts b/packages/vite/src/node/build.ts
index dfaab8362784c5..ec9173e18afed4 100644
--- a/packages/vite/src/node/build.ts
+++ b/packages/vite/src/node/build.ts
@@ -35,6 +35,7 @@ import {
   joinUrlSegments,
   normalizePath,
   requireResolveFromRootWithFallback,
+  withTrailingSlash,
 } from './utils'
 import { manifestPlugin } from './plugins/manifest'
 import type { Logger } from './logger'
@@ -714,7 +715,7 @@ function prepareOutDir(
     for (const outDir of nonDuplicateDirs) {
       if (
         fs.existsSync(outDir) &&
-        !normalizePath(outDir).startsWith(config.root + '/')
+        !normalizePath(outDir).startsWith(withTrailingSlash(config.root))
       ) {
         // warn if outDir is outside of root
         config.logger.warn(
@@ -1240,5 +1241,9 @@ export const toOutputFilePathInHtml = toOutputFilePathWithoutRuntime
 function areSeparateFolders(a: string, b: string) {
   const na = normalizePath(a)
   const nb = normalizePath(b)
-  return na !== nb && !na.startsWith(nb + '/') && !nb.startsWith(na + '/')
+  return (
+    na !== nb &&
+    !na.startsWith(withTrailingSlash(nb)) &&
+    !nb.startsWith(withTrailingSlash(na))
+  )
 }
diff --git a/packages/vite/src/node/config.ts b/packages/vite/src/node/config.ts
index f73ae2ae703e1c..b85788422672c1 100644
--- a/packages/vite/src/node/config.ts
+++ b/packages/vite/src/node/config.ts
@@ -39,6 +39,7 @@ import {
   mergeConfig,
   normalizeAlias,
   normalizePath,
+  withTrailingSlash,
 } from './utils'
 import {
   createPluginHookUtils,
@@ -680,7 +681,7 @@ export async function resolveConfig(
     ),
     inlineConfig,
     root: resolvedRoot,
-    base: resolvedBase.endsWith('/') ? resolvedBase : resolvedBase + '/',
+    base: withTrailingSlash(resolvedBase),
     rawBase: resolvedBase,
     resolve: resolveOptions,
     publicDir: resolvedPublicDir,
@@ -856,7 +857,7 @@ assetFileNames isn't equal for every build.rollupOptions.output. A single patter
   ) {
     resolved.logger.warn(
       colors.yellow(`
-(!) Experimental legacy.buildSsrCjsExternalHeuristics and ssr.format: 'cjs' are going to be removed in Vite 5. 
+(!) Experimental legacy.buildSsrCjsExternalHeuristics and ssr.format: 'cjs' are going to be removed in Vite 5.
     Find more information and give feedback at https://github.com/vitejs/vite/discussions/13816.
 `),
     )
diff --git a/packages/vite/src/node/plugins/asset.ts b/packages/vite/src/node/plugins/asset.ts
index 2c298a94c31f5a..d16130b58c01b9 100644
--- a/packages/vite/src/node/plugins/asset.ts
+++ b/packages/vite/src/node/plugins/asset.ts
@@ -23,6 +23,7 @@ import {
   joinUrlSegments,
   normalizePath,
   removeLeadingSlash,
+  withTrailingSlash,
 } from '../utils'
 import { FS_PREFIX } from '../constants'
 
@@ -229,7 +230,11 @@ export function checkPublicFile(
     return
   }
   const publicFile = path.join(publicDir, cleanUrl(url))
-  if (!publicFile.startsWith(publicDir)) {
+  if (
+    !normalizePath(publicFile).startsWith(
+      withTrailingSlash(normalizePath(publicDir)),
+    )
+  ) {
     // can happen if URL starts with '../'
     return
   }
@@ -257,7 +262,7 @@ function fileToDevUrl(id: string, config: ResolvedConfig) {
   if (checkPublicFile(id, config)) {
     // in public dir, keep the url as-is
     rtn = id
-  } else if (id.startsWith(config.root)) {
+  } else if (id.startsWith(withTrailingSlash(config.root))) {
     // in project root, infer short public path
     rtn = '/' + path.posix.relative(config.root, id)
   } else {
diff --git a/packages/vite/src/node/plugins/importAnalysis.ts b/packages/vite/src/node/plugins/importAnalysis.ts
index 620fa38175d19d..814aa9187a9ce0 100644
--- a/packages/vite/src/node/plugins/importAnalysis.ts
+++ b/packages/vite/src/node/plugins/importAnalysis.ts
@@ -44,6 +44,7 @@ import {
   timeFrom,
   transformStableResult,
   unwrapId,
+  withTrailingSlash,
   wrapId,
 } from '../utils'
 import { getDepOptimizationConfig } from '../config'
@@ -335,7 +336,7 @@ export function importAnalysisPlugin(config: ResolvedConfig): Plugin {
 
         // normalize all imports into resolved URLs
         // e.g. `import 'foo'` -> `import '/@fs/.../node_modules/foo/index.js'`
-        if (resolved.id.startsWith(root + '/')) {
+        if (resolved.id.startsWith(withTrailingSlash(root))) {
           // in root: infer short absolute path from root
           url = resolved.id.slice(root.length)
         } else if (
@@ -672,7 +673,7 @@ export function importAnalysisPlugin(config: ResolvedConfig): Plugin {
                 config.logger.error(e.message, { error: e })
               })
             }
-          } else if (!importer.startsWith(clientDir)) {
+          } else if (!importer.startsWith(withTrailingSlash(clientDir))) {
             if (!isInNodeModules(importer)) {
               // check @vite-ignore which suppresses dynamic import warning
               const hasViteIgnore = hasViteIgnoreRE.test(
diff --git a/packages/vite/src/node/plugins/importAnalysisBuild.ts b/packages/vite/src/node/plugins/importAnalysisBuild.ts
index 1d046eb49f581e..1889790463dae8 100644
--- a/packages/vite/src/node/plugins/importAnalysisBuild.ts
+++ b/packages/vite/src/node/plugins/importAnalysisBuild.ts
@@ -16,6 +16,7 @@ import {
   isInNodeModules,
   moduleListContains,
   numberToPos,
+  withTrailingSlash,
 } from '../utils'
 import type { Plugin } from '../plugin'
 import { getDepOptimizationConfig } from '../config'
@@ -271,7 +272,7 @@ export function buildImportAnalysisPlugin(config: ResolvedConfig): Plugin {
 
         // normalize all imports into resolved URLs
         // e.g. `import 'foo'` -> `import '/@fs/.../node_modules/foo/index.js'`
-        if (resolved.id.startsWith(root + '/')) {
+        if (resolved.id.startsWith(withTrailingSlash(root))) {
           // in root: infer short absolute path from root
           url = resolved.id.slice(root.length)
         } else {
diff --git a/packages/vite/src/node/plugins/preAlias.ts b/packages/vite/src/node/plugins/preAlias.ts
index 931db79d231bf7..cd86bac770d823 100644
--- a/packages/vite/src/node/plugins/preAlias.ts
+++ b/packages/vite/src/node/plugins/preAlias.ts
@@ -14,6 +14,7 @@ import {
   isInNodeModules,
   isOptimizable,
   moduleListContains,
+  withTrailingSlash,
 } from '../utils'
 import { getDepsOptimizer } from '../optimizer'
 import { tryOptimizedResolve } from './resolve'
@@ -114,7 +115,7 @@ function matches(pattern: string | RegExp, importee: string) {
   if (importee === pattern) {
     return true
   }
-  return importee.startsWith(pattern + '/')
+  return importee.startsWith(withTrailingSlash(pattern))
 }
 
 function getAliasPatterns(
diff --git a/packages/vite/src/node/plugins/reporter.ts b/packages/vite/src/node/plugins/reporter.ts
index cbcb0409d1e3f0..74ffe11246e8ad 100644
--- a/packages/vite/src/node/plugins/reporter.ts
+++ b/packages/vite/src/node/plugins/reporter.ts
@@ -4,7 +4,12 @@ import { promisify } from 'node:util'
 import colors from 'picocolors'
 import type { Plugin } from 'rollup'
 import type { ResolvedConfig } from '../config'
-import { isDefined, isInNodeModules, normalizePath } from '../utils'
+import {
+  isDefined,
+  isInNodeModules,
+  normalizePath,
+  withTrailingSlash,
+} from '../utils'
 import { LogLevels } from '../logger'
 
 const groups = [
@@ -243,9 +248,10 @@ export function buildReporterPlugin(config: ResolvedConfig): Plugin {
               group.name === 'JS' && entry.size / 1000 > chunkLimit
             if (isLarge) hasLargeChunks = true
             const sizeColor = isLarge ? colors.yellow : colors.dim
-            let log = colors.dim(relativeOutDir + '/')
+            let log = colors.dim(withTrailingSlash(relativeOutDir))
             log +=
-              !config.build.lib && entry.name.startsWith(assetsDir)
+              !config.build.lib &&
+              entry.name.startsWith(withTrailingSlash(assetsDir))
                 ? colors.dim(assetsDir) +
                   group.color(
                     entry.name
diff --git a/packages/vite/src/node/plugins/resolve.ts b/packages/vite/src/node/plugins/resolve.ts
index 63841d398c5256..26c30b9a9c9edc 100644
--- a/packages/vite/src/node/plugins/resolve.ts
+++ b/packages/vite/src/node/plugins/resolve.ts
@@ -36,6 +36,7 @@ import {
   safeRealpathSync,
   slash,
   tryStatSync,
+  withTrailingSlash,
 } from '../utils'
 import { optimizedDepInfoFromFile, optimizedDepInfoFromId } from '../optimizer'
 import type { DepsOptimizer } from '../optimizer'
@@ -228,7 +229,11 @@ export function resolvePlugin(resolveOptions: InternalResolveOptions): Plugin {
 
       // URL
       // /foo -> /fs-root/foo
-      if (asSrc && id[0] === '/' && (rootInRoot || !id.startsWith(root))) {
+      if (
+        asSrc &&
+        id[0] === '/' &&
+        (rootInRoot || !id.startsWith(withTrailingSlash(root)))
+      ) {
         const fsPath = path.resolve(root, id.slice(1))
         if ((res = tryFsResolve(fsPath, options))) {
           debug?.(`[url] ${colors.cyan(id)} -> ${colors.dim(res)}`)
@@ -939,7 +944,7 @@ export async function tryOptimizedResolve(
     }
 
     // match by src to correctly identify if id belongs to nested dependency
-    if (optimizedData.src.startsWith(idPkgDir)) {
+    if (optimizedData.src.startsWith(withTrailingSlash(idPkgDir))) {
       return depsOptimizer.getOptimizedDepId(optimizedData)
     }
   }
diff --git a/packages/vite/src/node/server/hmr.ts b/packages/vite/src/node/server/hmr.ts
index e72b1ebdf05338..f708b1114ed3cd 100644
--- a/packages/vite/src/node/server/hmr.ts
+++ b/packages/vite/src/node/server/hmr.ts
@@ -5,7 +5,13 @@ import colors from 'picocolors'
 import type { Update } from 'types/hmrPayload'
 import type { RollupError } from 'rollup'
 import { CLIENT_DIR } from '../constants'
-import { createDebugger, normalizePath, unique, wrapId } from '../utils'
+import {
+  createDebugger,
+  normalizePath,
+  unique,
+  withTrailingSlash,
+  wrapId,
+} from '../utils'
 import type { ViteDevServer } from '..'
 import { isCSSRequest } from '../plugins/css'
 import { getAffectedGlobModules } from '../plugins/importMetaGlob'
@@ -38,7 +44,9 @@ export interface HmrContext {
 }
 
 export function getShortName(file: string, root: string): string {
-  return file.startsWith(root + '/') ? path.posix.relative(root, file) : file
+  return file.startsWith(withTrailingSlash(root))
+    ? path.posix.relative(root, file)
+    : file
 }
 
 export async function handleHMRUpdate(
@@ -81,7 +89,7 @@ export async function handleHMRUpdate(
   debugHmr?.(`[file change] ${colors.dim(shortFile)}`)
 
   // (dev only) the client itself cannot be hot updated.
-  if (file.startsWith(normalizedClientDir)) {
+  if (file.startsWith(withTrailingSlash(normalizedClientDir))) {
     ws.send({
       type: 'full-reload',
       path: '*',
diff --git a/packages/vite/src/node/server/middlewares/base.ts b/packages/vite/src/node/server/middlewares/base.ts
index cba4582486f8a9..c6af2302aef3d9 100644
--- a/packages/vite/src/node/server/middlewares/base.ts
+++ b/packages/vite/src/node/server/middlewares/base.ts
@@ -1,6 +1,6 @@
 import type { Connect } from 'dep-types/connect'
 import type { ViteDevServer } from '..'
-import { joinUrlSegments, stripBase } from '../../utils'
+import { joinUrlSegments, stripBase, withTrailingSlash } from '../../utils'
 
 // this middleware is only active when (base !== '/')
 
@@ -36,7 +36,7 @@ export function baseMiddleware({
     } else if (req.headers.accept?.includes('text/html')) {
       // non-based page visit
       const redirectPath =
-        url + '/' !== base ? joinUrlSegments(base, url) : base
+        withTrailingSlash(url) !== base ? joinUrlSegments(base, url) : base
       res.writeHead(404, {
         'Content-Type': 'text/html',
       })
diff --git a/packages/vite/src/node/server/middlewares/static.ts b/packages/vite/src/node/server/middlewares/static.ts
index d1e7073179415b..8acc9e681b4e37 100644
--- a/packages/vite/src/node/server/middlewares/static.ts
+++ b/packages/vite/src/node/server/middlewares/static.ts
@@ -19,6 +19,7 @@ import {
   removeLeadingSlash,
   shouldServeFile,
   slash,
+  withTrailingSlash,
 } from '../../utils'
 
 const knownJavascriptExtensionRE = /\.[tj]sx?$/
@@ -118,7 +119,7 @@ export function serveStaticMiddleware(
     }
     if (redirectedPathname) {
       // dir is pre-normalized to posix style
-      if (redirectedPathname.startsWith(dir)) {
+      if (redirectedPathname.startsWith(withTrailingSlash(dir))) {
         redirectedPathname = redirectedPathname.slice(dir.length)
       }
     }
@@ -129,7 +130,7 @@ export function serveStaticMiddleware(
       resolvedPathname[resolvedPathname.length - 1] === '/' &&
       fileUrl[fileUrl.length - 1] !== '/'
     ) {
-      fileUrl = fileUrl + '/'
+      fileUrl = withTrailingSlash(fileUrl)
     }
     if (!ensureServingAccess(fileUrl, server, res, next)) {
       return
diff --git a/packages/vite/src/node/server/middlewares/transform.ts b/packages/vite/src/node/server/middlewares/transform.ts
index 737fb92f7d0fbc..f85b12a46202f4 100644
--- a/packages/vite/src/node/server/middlewares/transform.ts
+++ b/packages/vite/src/node/server/middlewares/transform.ts
@@ -16,6 +16,7 @@ import {
   removeImportQuery,
   removeTimestampQuery,
   unwrapId,
+  withTrailingSlash,
 } from '../../utils'
 import { send } from '../send'
 import { ERR_LOAD_URL, transformRequest } from '../transformRequest'
@@ -129,10 +130,10 @@ export function transformMiddleware(
       // check if public dir is inside root dir
       const publicDir = normalizePath(server.config.publicDir)
       const rootDir = normalizePath(server.config.root)
-      if (publicDir.startsWith(rootDir)) {
+      if (publicDir.startsWith(withTrailingSlash(rootDir))) {
         const publicPath = `${publicDir.slice(rootDir.length)}/`
         // warn explicit public paths
-        if (url.startsWith(publicPath)) {
+        if (url.startsWith(withTrailingSlash(publicPath))) {
           let warning: string
 
           if (isImportRequest(url)) {
diff --git a/packages/vite/src/node/ssr/ssrExternal.ts b/packages/vite/src/node/ssr/ssrExternal.ts
index 9a5bc28b39b9ee..99001f3614f330 100644
--- a/packages/vite/src/node/ssr/ssrExternal.ts
+++ b/packages/vite/src/node/ssr/ssrExternal.ts
@@ -13,6 +13,7 @@ import {
   isInNodeModules,
   lookupFile,
   normalizePath,
+  withTrailingSlash,
 } from '../utils'
 import type { Logger, ResolvedConfig } from '..'
 import { resolvePackageData } from '../packages'
@@ -340,7 +341,10 @@ export function cjsShouldExternalizeForSSR(
     }
     // deep imports, check ext before externalizing - only externalize
     // extension-less imports and explicit .js imports
-    if (id.startsWith(e + '/') && (!path.extname(id) || id.endsWith('.js'))) {
+    if (
+      id.startsWith(withTrailingSlash(e)) &&
+      (!path.extname(id) || id.endsWith('.js'))
+    ) {
       return true
     }
   })
diff --git a/packages/vite/src/node/utils.ts b/packages/vite/src/node/utils.ts
index 27a619947c0b0d..66d071dddc7bbd 100644
--- a/packages/vite/src/node/utils.ts
+++ b/packages/vite/src/node/utils.ts
@@ -123,7 +123,9 @@ export function moduleListContains(
   moduleList: string[] | undefined,
   id: string,
 ): boolean | undefined {
-  return moduleList?.some((m) => m === id || id.startsWith(m + '/'))
+  return moduleList?.some(
+    (m) => m === id || id.startsWith(withTrailingSlash(m)),
+  )
 }
 
 export function isOptimizable(
@@ -221,6 +223,13 @@ export function fsPathFromUrl(url: string): string {
   return fsPathFromId(cleanUrl(url))
 }
 
+export function withTrailingSlash(path: string): string {
+  if (path[path.length - 1] !== '/') {
+    return `${path}/`
+  }
+  return path
+}
+
 /**
  * Check if dir is a parent of file
  *
@@ -231,9 +240,7 @@ export function fsPathFromUrl(url: string): string {
  * @returns true if dir is a parent of file
  */
 export function isParentDirectory(dir: string, file: string): boolean {
-  if (dir[dir.length - 1] !== '/') {
-    dir = `${dir}/`
-  }
+  dir = withTrailingSlash(dir)
   return (
     file.startsWith(dir) ||
     (isCaseInsensitiveFS && file.toLowerCase().startsWith(dir.toLowerCase()))
@@ -644,7 +651,7 @@ export function ensureWatchedFile(
   if (
     file &&
     // only need to watch if out of root
-    !file.startsWith(root + '/') &&
+    !file.startsWith(withTrailingSlash(root)) &&
     // some rollup plugins use null bytes for private resolved Ids
     !file.includes('\0') &&
     fs.existsSync(file)
@@ -1222,7 +1229,7 @@ export function stripBase(path: string, base: string): string {
   if (path === base) {
     return '/'
   }
-  const devBase = base[base.length - 1] === '/' ? base : base + '/'
+  const devBase = withTrailingSlash(base)
   return path.startsWith(devBase) ? path.slice(devBase.length - 1) : path
 }