diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index fbb0458..7bc2626 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -93,6 +93,9 @@ jobs:
       # build lint plugins before linting
       - name: Build lint plugins
         run: npm run build:lint:ci
+      # check formatting
+      - name: Check Formatting
+        run: npm run format:ci
       # lint
       - name: Lint
         run: npm run lint:ci
diff --git a/package-lock.json b/package-lock.json
index e4755ce..438bb8b 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -14836,7 +14836,7 @@
     },
     "packages/branch-utilities": {
       "name": "@shiftcode/branch-utilities",
-      "version": "5.0.0",
+      "version": "5.0.1-pr53.1",
       "license": "MIT",
       "engines": {
         "node": "^20.0.0 || ^22.0.0"
@@ -14847,10 +14847,10 @@
     },
     "packages/eslint-config-recommended": {
       "name": "@shiftcode/eslint-config-recommended",
-      "version": "5.0.0",
+      "version": "5.0.1-pr53.1",
       "license": "UNLICENSED",
       "dependencies": {
-        "@shiftcode/eslint-plugin-rules": "^4.0.0",
+        "@shiftcode/eslint-plugin-rules": "^4.0.1-pr53.1",
         "@typescript-eslint/eslint-plugin": "^8.18.0",
         "@typescript-eslint/parser": "^8.18.0",
         "eslint": "^8.56.0",
@@ -14888,7 +14888,7 @@
     },
     "packages/eslint-plugin-rules": {
       "name": "@shiftcode/eslint-plugin-rules",
-      "version": "4.0.0",
+      "version": "4.0.1-pr53.1",
       "license": "UNLICENSED",
       "dependencies": {
         "@eslint/eslintrc": "^2.1.4",
@@ -14907,21 +14907,21 @@
     },
     "packages/logger": {
       "name": "@shiftcode/logger",
-      "version": "3.0.0",
+      "version": "3.0.1-pr53.5",
       "license": "UNLICENSED",
       "devDependencies": {
-        "@shiftcode/utilities": "^4.0.0"
+        "@shiftcode/utilities": "^4.1.0-pr53.5"
       },
       "engines": {
         "node": "^20.0.0 || ^22.0.0"
       },
       "peerDependencies": {
-        "@shiftcode/utilities": "^4.0.0 || ^4.0.0-pr45"
+        "@shiftcode/utilities": "^4.0.0 || ^4.0.0-pr53"
       }
     },
     "packages/publish-helper": {
       "name": "@shiftcode/publish-helper",
-      "version": "4.1.0",
+      "version": "4.1.1-pr53.1",
       "license": "MIT",
       "dependencies": {
         "conventional-changelog-angular": "^8.0.0",
@@ -14932,7 +14932,7 @@
         "publish-lib": "dist/publish-lib.js"
       },
       "devDependencies": {
-        "@shiftcode/branch-utilities": "^5.0.0",
+        "@shiftcode/branch-utilities": "^5.0.1-pr53.1",
         "@types/yargs": "^17.0.32"
       },
       "engines": {
@@ -14957,7 +14957,7 @@
     },
     "packages/utilities": {
       "name": "@shiftcode/utilities",
-      "version": "4.0.0",
+      "version": "4.1.0-pr53.5",
       "license": "MIT",
       "engines": {
         "node": "^20.0.0 || ^22.0.0"
diff --git a/package.json b/package.json
index 17ba8b8..1b203e0 100644
--- a/package.json
+++ b/package.json
@@ -11,9 +11,10 @@
   "scripts": {
     "build:ci": "lerna run build",
     "build:lint:ci": "lerna run build:lint:ci",
+    "format": "lerna run format",
+    "format:ci": "lerna run format:ci",
     "lint:ci": "lerna run lint:ci",
     "prepare": "husky",
-    "prettier": "lerna run prettier",
     "publish-libs": "node packages/publish-helper/dist/publish-lib",
     "test:ci": "lerna run test:ci"
   },
diff --git a/packages/branch-utilities/.lintstagedrc.yml b/packages/branch-utilities/.lintstagedrc.yml
index bf45dc5..a033e03 100644
--- a/packages/branch-utilities/.lintstagedrc.yml
+++ b/packages/branch-utilities/.lintstagedrc.yml
@@ -1,7 +1,6 @@
-# we use eslint instead of ng lint, because we can't use --project (tsconfig specifying files with include, exclude)
-# and --files argument pointing to other files
-src/{**/,}*.ts,test/{**/,}*.ts:
-  - npm run prettier:staged
+# Reformat all .ts / .js
+"**/*.(t|j)s":
+  - npm run format:staged
   - npm run lint:staged
 
 # sort package.json keys
diff --git a/packages/branch-utilities/package.json b/packages/branch-utilities/package.json
index 093b880..a1f2c49 100644
--- a/packages/branch-utilities/package.json
+++ b/packages/branch-utilities/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@shiftcode/branch-utilities",
-  "version": "5.0.0",
+  "version": "5.0.1-pr53.1",
   "description": "Utilities for local and ci to get branch name and stage",
   "repository": "https://github.com/shiftcode/sc-commons-public",
   "license": "MIT",
@@ -16,13 +16,15 @@
   "scripts": {
     "prebuild": "rm -rf ./dist",
     "build": "tsc",
+    "format": "npm run format:base -- --write",
+    "format:base": "prettier --config ../../.prettierrc.yml '{src,e2e,test}/**/*.ts'",
+    "format:ci": "npm run format:base -- --check",
+    "format:staged": "prettier --write --config ../../.prettierrc.yml",
     "lint": "npm run lint:src:fix",
     "lint:ci": "npm run lint:src",
     "lint:src": "eslint ./src",
     "lint:src:fix": "eslint ./src --cache --fix",
     "lint:staged": "eslint --fix --cache",
-    "prettier": "prettier --write --config ../../.prettierrc.yml '{src,e2e,test}/**/*.ts'",
-    "prettier:staged": "prettier --write --config ../../.prettierrc.yml",
     "prepublish": "node ../publish-helper/dist/prepare-dist.js",
     "test": "NODE_OPTIONS=\"--experimental-vm-modules --trace-warnings\" npx jest --config jest.config.js",
     "test:ci": "npm run test",
diff --git a/packages/branch-utilities/src/lib/base.utils.spec.ts b/packages/branch-utilities/src/lib/base.utils.spec.ts
index e57ca14..befd57d 100644
--- a/packages/branch-utilities/src/lib/base.utils.spec.ts
+++ b/packages/branch-utilities/src/lib/base.utils.spec.ts
@@ -81,9 +81,10 @@ describe('base utils', () => {
   })
 
   describe('parseBranchName', () => {
-
     test('works when valid pattern', () => {
-      expect(parseBranchName('#7-abc')).toEqual({ branchId: 7, branchName: 'abc' } satisfies ReturnType<typeof parseBranchName>)
+      expect(parseBranchName('#7-abc')).toEqual({ branchId: 7, branchName: 'abc' } satisfies ReturnType<
+        typeof parseBranchName
+      >)
 
       expect(parseBranchName('#72-abc').branchId).toBe(72)
       expect(parseBranchName('#000-int').branchId).toBe(0)
@@ -94,8 +95,12 @@ describe('base utils', () => {
     })
 
     test('works for github copilot created branches', () => {
-      expect(parseBranchName('copilot/fix-123')).toEqual({ branchId: 123, branchName: 'fix' } satisfies ReturnType<typeof parseBranchName>)
-      expect(parseBranchName('copilot/feat-123')).toEqual({ branchId: 123, branchName: 'feat' } satisfies ReturnType<typeof parseBranchName>)
+      expect(parseBranchName('copilot/fix-123')).toEqual({ branchId: 123, branchName: 'fix' } satisfies ReturnType<
+        typeof parseBranchName
+      >)
+      expect(parseBranchName('copilot/feat-123')).toEqual({ branchId: 123, branchName: 'feat' } satisfies ReturnType<
+        typeof parseBranchName
+      >)
     })
 
     test('throws when invalid pattern', () => {
diff --git a/packages/branch-utilities/src/lib/base.utils.ts b/packages/branch-utilities/src/lib/base.utils.ts
index 5f39748..c906fcb 100644
--- a/packages/branch-utilities/src/lib/base.utils.ts
+++ b/packages/branch-utilities/src/lib/base.utils.ts
@@ -90,9 +90,11 @@ export function getBranchInfo(env: unknown, branchName?: string): BranchInfo {
 }
 
 export function isFullBranchOverrideDefined(envVars: unknown): envVars is CustomScOverrideEnv {
-  return envVars !== null
-    && typeof (envVars as CustomScOverrideEnv).SC_OVERRIDE_BRANCH_NAME ==='string'
-    && typeof (envVars as CustomScOverrideEnv).SC_OVERRIDE_IS_PR ==='string'
+  return (
+    envVars !== null &&
+    typeof (envVars as CustomScOverrideEnv).SC_OVERRIDE_BRANCH_NAME === 'string' &&
+    typeof (envVars as CustomScOverrideEnv).SC_OVERRIDE_IS_PR === 'string'
+  )
 }
 
 export function getBranchNameOverride(env: CustomScOverrideEnv): string {
diff --git a/packages/eslint-config-recommended/.lintstagedrc.yml b/packages/eslint-config-recommended/.lintstagedrc.yml
index 69f89f4..bb9649d 100644
--- a/packages/eslint-config-recommended/.lintstagedrc.yml
+++ b/packages/eslint-config-recommended/.lintstagedrc.yml
@@ -1,7 +1,6 @@
-# we use eslint instead of ng lint, because we can't use --project (tsconfig specifying files with include, exclude)
-# and --files argument pointing to other files
-src/{**/,}*.ts,test/{**/,}*.ts:
-  - npm run prettier:staged
+# Reformat all .ts / .js
+"**/*.(t|j)s":
+  - npm run format:staged
   - npm run lint:staged
 
 # sort package.json keys
diff --git a/packages/eslint-config-recommended/package.json b/packages/eslint-config-recommended/package.json
index 4e9909b..b63127e 100644
--- a/packages/eslint-config-recommended/package.json
+++ b/packages/eslint-config-recommended/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@shiftcode/eslint-config-recommended",
-  "version": "5.0.0",
+  "version": "5.0.1-pr53.1",
   "description": "default shiftcode config for eslint",
   "repository": "https://github.com/shiftcode/sc-commons-public",
   "license": "UNLICENSED",
@@ -24,19 +24,21 @@
     "prebuild": "rm -rf ./dist",
     "build": "tsc",
     "build:lint:ci": "npm run build",
+    "format": "npm run format:base -- --write",
+    "format:base": "prettier --config ../../.prettierrc.yml '{src,e2e,test}/**/*.ts'",
+    "format:ci": "npm run format:base -- --check",
+    "format:staged": "prettier --write --config ../../.prettierrc.yml",
     "lint": "npm run lint:src:fix",
     "lint:ci": "npm run lint:src",
     "lint:src": "eslint ./src",
     "lint:src:fix": "eslint ./src --cache --fix",
     "lint:staged": "eslint --fix --cache",
-    "prettier": "prettier --write --config ../../.prettierrc.yml '{src,e2e,test}/**/*.ts'",
-    "prettier:staged": "prettier --write --config ../../.prettierrc.yml",
     "prepublish": "node ../publish-helper/dist/prepare-dist.js",
     "test": "echo 'Error: no test specificed'",
     "test:ci": "npm run test"
   },
   "dependencies": {
-    "@shiftcode/eslint-plugin-rules": "^4.0.0",
+    "@shiftcode/eslint-plugin-rules": "^4.0.1-pr53.1",
     "@typescript-eslint/eslint-plugin": "^8.18.0",
     "@typescript-eslint/parser": "^8.18.0",
     "eslint": "^8.56.0",
diff --git a/packages/eslint-plugin-rules/.lintstagedrc.yml b/packages/eslint-plugin-rules/.lintstagedrc.yml
index bf45dc5..a033e03 100644
--- a/packages/eslint-plugin-rules/.lintstagedrc.yml
+++ b/packages/eslint-plugin-rules/.lintstagedrc.yml
@@ -1,7 +1,6 @@
-# we use eslint instead of ng lint, because we can't use --project (tsconfig specifying files with include, exclude)
-# and --files argument pointing to other files
-src/{**/,}*.ts,test/{**/,}*.ts:
-  - npm run prettier:staged
+# Reformat all .ts / .js
+"**/*.(t|j)s":
+  - npm run format:staged
   - npm run lint:staged
 
 # sort package.json keys
diff --git a/packages/eslint-plugin-rules/package.json b/packages/eslint-plugin-rules/package.json
index d587976..d446a75 100644
--- a/packages/eslint-plugin-rules/package.json
+++ b/packages/eslint-plugin-rules/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@shiftcode/eslint-plugin-rules",
-  "version": "4.0.0",
+  "version": "4.0.1-pr53.1",
   "description": "eslint-rules for shiftcode-specific eslint rules",
   "repository": "https://github.com/shiftcode/sc-commons-public",
   "license": "UNLICENSED",
@@ -14,13 +14,15 @@
     "prebuild": "rm -rf ./dist",
     "build": "tsc",
     "build:lint:ci": "npm run build",
+    "format": "npm run format:base -- --write",
+    "format:base": "prettier --config ../../.prettierrc.yml '{src,e2e,test}/**/*.ts'",
+    "format:ci": "npm run format:base -- --check",
+    "format:staged": "prettier --write --config ../../.prettierrc.yml",
     "lint": "npm run lint:src:fix",
     "lint:ci": "npm run lint:src",
     "lint:src": "eslint ./src",
     "lint:src:fix": "eslint ./src --cache --fix",
     "lint:staged": "eslint --fix --cache",
-    "prettier": "prettier --write --config ../../.prettierrc.yml '{src,e2e,test}/**/*.ts'",
-    "prettier:staged": "prettier --write --config ../../.prettierrc.yml",
     "prepublish": "node ../publish-helper/dist/prepare-dist.js",
     "test": "jest",
     "test:ci": "npm run test"
diff --git a/packages/logger/.lintstagedrc.yml b/packages/logger/.lintstagedrc.yml
index 3830437..a033e03 100644
--- a/packages/logger/.lintstagedrc.yml
+++ b/packages/logger/.lintstagedrc.yml
@@ -1,6 +1,6 @@
 # Reformat all .ts / .js
 "**/*.(t|j)s":
-  - npm run prettier:staged
+  - npm run format:staged
   - npm run lint:staged
 
 # sort package.json keys
diff --git a/packages/logger/package.json b/packages/logger/package.json
index 5f42e0d..44d0330 100644
--- a/packages/logger/package.json
+++ b/packages/logger/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@shiftcode/logger",
-  "version": "3.0.0",
+  "version": "3.0.1-pr53.5",
   "description": "logger for local and aws lambda execution",
   "repository": "https://github.com/shiftcode/sc-commons-public",
   "license": "UNLICENSED",
@@ -20,6 +20,10 @@
   "scripts": {
     "prebuild": "rm -rf ./dist",
     "build": "tsc",
+    "format": "npm run format:base -- --write",
+    "format:base": "prettier --config ../../.prettierrc.yml '{src,e2e,test}/**/*.ts'",
+    "format:ci": "npm run format:base -- --check",
+    "format:staged": "prettier --write --config ../../.prettierrc.yml",
     "lint": "npm run lint:src:fix && npm run lint:test:fix",
     "lint:ci": "npm run lint:src && npm run lint:test",
     "lint:src": "eslint ./src",
@@ -27,18 +31,16 @@
     "lint:staged": "npm run lint",
     "lint:test": "eslint ./test",
     "lint:test:fix": "eslint ./test --cache --fix",
-    "prettier": "prettier --write --config ../../.prettierrc.yml '{src,e2e,test}/**/*.ts'",
-    "prettier:staged": "prettier --write --config ../../.prettierrc.yml",
     "prepublish": "node ../publish-helper/dist/prepare-dist.js",
     "test": "NODE_OPTIONS=\"--experimental-vm-modules --trace-warnings\" npx jest --config jest.config.js",
     "test:ci": "npm run test",
     "test:watch": "npm run test -- --watch"
   },
   "devDependencies": {
-    "@shiftcode/utilities": "^4.0.0"
+    "@shiftcode/utilities": "^4.1.0-pr53.5"
   },
   "peerDependencies": {
-    "@shiftcode/utilities": "^4.0.0 || ^4.0.0-pr45"
+    "@shiftcode/utilities": "^4.0.0 || ^4.0.0-pr53"
   },
   "engines": {
     "node": "^20.0.0 || ^22.0.0"
diff --git a/packages/publish-helper/.lintstagedrc.yml b/packages/publish-helper/.lintstagedrc.yml
index bf45dc5..a033e03 100644
--- a/packages/publish-helper/.lintstagedrc.yml
+++ b/packages/publish-helper/.lintstagedrc.yml
@@ -1,7 +1,6 @@
-# we use eslint instead of ng lint, because we can't use --project (tsconfig specifying files with include, exclude)
-# and --files argument pointing to other files
-src/{**/,}*.ts,test/{**/,}*.ts:
-  - npm run prettier:staged
+# Reformat all .ts / .js
+"**/*.(t|j)s":
+  - npm run format:staged
   - npm run lint:staged
 
 # sort package.json keys
diff --git a/packages/publish-helper/package.json b/packages/publish-helper/package.json
index e8d6060..c2f570a 100644
--- a/packages/publish-helper/package.json
+++ b/packages/publish-helper/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@shiftcode/publish-helper",
-  "version": "4.1.0",
+  "version": "4.1.1-pr53.1",
   "description": "scripts for conventional (pre)releases",
   "repository": "https://github.com/shiftcode/sc-commons-public",
   "license": "MIT",
@@ -13,13 +13,15 @@
   "scripts": {
     "prebuild": "rm -rf ./dist",
     "build": "tsc",
+    "format": "npm run format:base -- --write",
+    "format:base": "prettier --config ../../.prettierrc.yml '{src,e2e,test}/**/*.ts'",
+    "format:ci": "npm run format:base -- --check",
+    "format:staged": "prettier --write --config ../../.prettierrc.yml",
     "lint": "npm run lint:src:fix",
     "lint:ci": "npm run lint:src",
     "lint:src": "eslint ./src",
     "lint:src:fix": "eslint ./src --cache --fix",
     "lint:staged": "eslint --fix --cache",
-    "prettier": "prettier --write --config ../../.prettierrc.yml '{src,e2e,test}/**/*.ts'",
-    "prettier:staged": "prettier --write --config ../../.prettierrc.yml",
     "prepublish": "node ./dist/prepare-dist.js",
     "test": "NODE_OPTIONS=\"--experimental-vm-modules --trace-warnings\" npx jest --config jest.config.js --passWithNoTests",
     "test:ci": "npm run test",
@@ -30,7 +32,7 @@
     "yargs": "^17.7.2"
   },
   "devDependencies": {
-    "@shiftcode/branch-utilities": "^5.0.0",
+    "@shiftcode/branch-utilities": "^5.0.1-pr53.1",
     "@types/yargs": "^17.0.32"
   },
   "peerDependencies": {
diff --git a/packages/publish-helper/src/prepare-dist.ts b/packages/publish-helper/src/prepare-dist.ts
index 4d10f90..2685a5e 100644
--- a/packages/publish-helper/src/prepare-dist.ts
+++ b/packages/publish-helper/src/prepare-dist.ts
@@ -18,7 +18,7 @@ const argv = yargs(hideBin(process.argv)).option('include', {
   type: 'array',
   description: 'copy additional files into the dist folder',
   default: [],
-  string: true
+  string: true,
 }).argv
 
 function log(...args: any[]) {
diff --git a/packages/utilities/.lintstagedrc.yml b/packages/utilities/.lintstagedrc.yml
index bf45dc5..a033e03 100644
--- a/packages/utilities/.lintstagedrc.yml
+++ b/packages/utilities/.lintstagedrc.yml
@@ -1,7 +1,6 @@
-# we use eslint instead of ng lint, because we can't use --project (tsconfig specifying files with include, exclude)
-# and --files argument pointing to other files
-src/{**/,}*.ts,test/{**/,}*.ts:
-  - npm run prettier:staged
+# Reformat all .ts / .js
+"**/*.(t|j)s":
+  - npm run format:staged
   - npm run lint:staged
 
 # sort package.json keys
diff --git a/packages/utilities/package.json b/packages/utilities/package.json
index 80bb2ab..162f5b4 100644
--- a/packages/utilities/package.json
+++ b/packages/utilities/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@shiftcode/utilities",
-  "version": "4.0.0",
+  "version": "4.1.0-pr53.5",
   "description": "Contains some utilities",
   "repository": "https://github.com/shiftcode/sc-commons-public",
   "license": "MIT",
@@ -16,13 +16,15 @@
   "scripts": {
     "prebuild": "rm -rf ./dist",
     "build": "tsc",
+    "format": "npm run format:base -- --write",
+    "format:base": "prettier --config ../../.prettierrc.yml '{src,e2e,test}/**/*.ts'",
+    "format:ci": "npm run format:base -- --check",
+    "format:staged": "prettier --write --config ../../.prettierrc.yml",
     "lint": "npm run lint:src:fix",
     "lint:ci": "npm run lint:src",
     "lint:src": "eslint ./src",
     "lint:src:fix": "eslint ./src --cache --fix",
     "lint:staged": "eslint --fix --cache",
-    "prettier": "prettier --write --config ../../.prettierrc.yml '{src,e2e,test}/**/*.ts'",
-    "prettier:staged": "prettier --write --config ../../.prettierrc.yml",
     "prepublish": "node ../publish-helper/dist/prepare-dist.js",
     "test": "NODE_OPTIONS=\"--experimental-vm-modules --trace-warnings\" npx jest --config jest.config.js",
     "test:ci": "npm run test",
diff --git a/packages/utilities/src/index.ts b/packages/utilities/src/index.ts
index 417e7f5..0748aee 100644
--- a/packages/utilities/src/index.ts
+++ b/packages/utilities/src/index.ts
@@ -19,3 +19,10 @@ export * from './lib/type-utils/nullable.type.js'
 export * from './lib/type-utils/union-to-intersection.type.js'
 export * from './lib/string/words.js'
 export * from './lib/string/capitalize.function.js'
+export * from './lib/ts-guards/is-array.js'
+export * from './lib/ts-guards/is-boolean.js'
+export * from './lib/ts-guards/is-class.js'
+export * from './lib/ts-guards/is-date.js'
+export * from './lib/ts-guards/is-defined.js'
+export * from './lib/ts-guards/is-number.js'
+export * from './lib/ts-guards/is-string.js'
diff --git a/packages/utilities/src/lib/ts-guards/is-array.spec.ts b/packages/utilities/src/lib/ts-guards/is-array.spec.ts
new file mode 100644
index 0000000..02e36b1
--- /dev/null
+++ b/packages/utilities/src/lib/ts-guards/is-array.spec.ts
@@ -0,0 +1,23 @@
+import { isArray } from './is-array.js'
+
+describe('isArray', () => {
+  it('should return true for array values', () => {
+    expect(isArray([])).toBe(true)
+    expect(isArray([1, 2, 3])).toBe(true)
+    expect(isArray(['a', 'b', 'c'])).toBe(true)
+    expect(isArray([null, undefined])).toBe(true)
+    // eslint-disable-next-line @typescript-eslint/no-array-constructor
+    expect(isArray(new Array())).toBe(true)
+  })
+
+  it('should return false for non-array values', () => {
+    expect(isArray('array')).toBe(false)
+    expect(isArray(123)).toBe(false)
+    expect(isArray(true)).toBe(false)
+    expect(isArray(null)).toBe(false)
+    expect(isArray(undefined)).toBe(false)
+    expect(isArray({})).toBe(false)
+    expect(isArray(new Date())).toBe(false)
+    expect(isArray({ length: 0 })).toBe(false)
+  })
+})
diff --git a/packages/utilities/src/lib/ts-guards/is-array.ts b/packages/utilities/src/lib/ts-guards/is-array.ts
new file mode 100644
index 0000000..b783132
--- /dev/null
+++ b/packages/utilities/src/lib/ts-guards/is-array.ts
@@ -0,0 +1,3 @@
+export function isArray(value: unknown): value is unknown[] {
+  return Array.isArray(value)
+}
diff --git a/packages/utilities/src/lib/ts-guards/is-boolean.spec.ts b/packages/utilities/src/lib/ts-guards/is-boolean.spec.ts
new file mode 100644
index 0000000..520d1f6
--- /dev/null
+++ b/packages/utilities/src/lib/ts-guards/is-boolean.spec.ts
@@ -0,0 +1,20 @@
+import { isBoolean } from './is-boolean.js'
+
+describe('isBoolean', () => {
+  it('should return true for boolean values', () => {
+    expect(isBoolean(true)).toBe(true)
+    expect(isBoolean(false)).toBe(true)
+  })
+
+  it('should return false for non-boolean values', () => {
+    expect(isBoolean(1)).toBe(false)
+    expect(isBoolean(0)).toBe(false)
+    expect(isBoolean('true')).toBe(false)
+    expect(isBoolean('false')).toBe(false)
+    expect(isBoolean(null)).toBe(false)
+    expect(isBoolean(undefined)).toBe(false)
+    expect(isBoolean([])).toBe(false)
+    expect(isBoolean({})).toBe(false)
+    expect(isBoolean(new Date())).toBe(false)
+  })
+})
diff --git a/packages/utilities/src/lib/ts-guards/is-boolean.ts b/packages/utilities/src/lib/ts-guards/is-boolean.ts
new file mode 100644
index 0000000..9e60021
--- /dev/null
+++ b/packages/utilities/src/lib/ts-guards/is-boolean.ts
@@ -0,0 +1,3 @@
+export function isBoolean(value: unknown): value is boolean {
+  return typeof value === 'boolean'
+}
diff --git a/packages/utilities/src/lib/ts-guards/is-class.spec.ts b/packages/utilities/src/lib/ts-guards/is-class.spec.ts
new file mode 100644
index 0000000..93356e0
--- /dev/null
+++ b/packages/utilities/src/lib/ts-guards/is-class.spec.ts
@@ -0,0 +1,25 @@
+import { isClass } from './is-class.js'
+
+class TestClass {
+  constructor() {}
+
+  x() {}
+}
+
+describe('isClass', () => {
+  it('should return true for classes', () => {
+    expect(isClass(TestClass)).toBe(true)
+  })
+
+  it('should return false for non-class values', () => {
+    expect(isClass('string')).toBe(false)
+    expect(isClass(123)).toBe(false)
+    expect(isClass(true)).toBe(false)
+    expect(isClass(null)).toBe(false)
+    expect(isClass(undefined)).toBe(false)
+    expect(isClass([])).toBe(false)
+    expect(isClass({})).toBe(false)
+    expect(isClass(function y() {})).toBe(false)
+    expect(isClass(new TestClass().x)).toBe(false)
+  })
+})
diff --git a/packages/utilities/src/lib/ts-guards/is-class.ts b/packages/utilities/src/lib/ts-guards/is-class.ts
new file mode 100644
index 0000000..49bcd38
--- /dev/null
+++ b/packages/utilities/src/lib/ts-guards/is-class.ts
@@ -0,0 +1,5 @@
+export function isClass<T extends new (...args: any[]) => any>(v: T): v is T
+export function isClass(value: unknown): value is new (...args: any[]) => any
+export function isClass(value: unknown): value is new (...args: any[]) => any {
+  return typeof value === 'function' && /^\s*class\s+/.test(value.toString())
+}
diff --git a/packages/utilities/src/lib/ts-guards/is-date.spec.ts b/packages/utilities/src/lib/ts-guards/is-date.spec.ts
new file mode 100644
index 0000000..4026291
--- /dev/null
+++ b/packages/utilities/src/lib/ts-guards/is-date.spec.ts
@@ -0,0 +1,22 @@
+import { isDate } from './is-date.js'
+
+describe('isDate', () => {
+  it('should return true for Date objects', () => {
+    expect(isDate(new Date())).toBe(true)
+    expect(isDate(new Date('2023-01-01'))).toBe(true)
+    expect(isDate(new Date(2023, 0, 1))).toBe(true)
+    expect(isDate(new Date(Date.now()))).toBe(true)
+  })
+
+  it('should return false for non-Date values', () => {
+    expect(isDate('2023-01-01')).toBe(false)
+    expect(isDate(1672531200000)).toBe(false)
+    expect(isDate(true)).toBe(false)
+    expect(isDate(false)).toBe(false)
+    expect(isDate(null)).toBe(false)
+    expect(isDate(undefined)).toBe(false)
+    expect(isDate([])).toBe(false)
+    expect(isDate({})).toBe(false)
+    expect(isDate('hello')).toBe(false)
+  })
+})
diff --git a/packages/utilities/src/lib/ts-guards/is-date.ts b/packages/utilities/src/lib/ts-guards/is-date.ts
new file mode 100644
index 0000000..e698d74
--- /dev/null
+++ b/packages/utilities/src/lib/ts-guards/is-date.ts
@@ -0,0 +1,3 @@
+export function isDate(value: unknown): value is Date {
+  return value instanceof Date
+}
diff --git a/packages/utilities/src/lib/ts-guards/is-defined.spec.ts b/packages/utilities/src/lib/ts-guards/is-defined.spec.ts
new file mode 100644
index 0000000..8e54c8c
--- /dev/null
+++ b/packages/utilities/src/lib/ts-guards/is-defined.spec.ts
@@ -0,0 +1,18 @@
+import { isDefined } from './is-defined.js'
+
+describe('isDefined', () => {
+  it('should return true for defined values', () => {
+    expect(isDefined('')).toBe(true)
+    expect(isDefined(0)).toBe(true)
+    expect(isDefined(false)).toBe(true)
+    expect(isDefined([])).toBe(true)
+    expect(isDefined({})).toBe(true)
+    expect(isDefined('hello')).toBe(true)
+    expect(isDefined(123)).toBe(true)
+  })
+
+  it('should return false for undefined values', () => {
+    expect(isDefined(undefined)).toBe(false)
+    expect(isDefined(null)).toBe(false)
+  })
+})
diff --git a/packages/utilities/src/lib/ts-guards/is-defined.ts b/packages/utilities/src/lib/ts-guards/is-defined.ts
new file mode 100644
index 0000000..8ccf63b
--- /dev/null
+++ b/packages/utilities/src/lib/ts-guards/is-defined.ts
@@ -0,0 +1,6 @@
+/**
+ * Checks if a value is defined (not undefined or null).
+ */
+export function isDefined<T>(value: T | undefined | null): value is T {
+  return value !== undefined && value !== null
+}
diff --git a/packages/utilities/src/lib/ts-guards/is-number.spec.ts b/packages/utilities/src/lib/ts-guards/is-number.spec.ts
new file mode 100644
index 0000000..2061ea1
--- /dev/null
+++ b/packages/utilities/src/lib/ts-guards/is-number.spec.ts
@@ -0,0 +1,27 @@
+import { isNumber } from './is-number.js'
+
+describe('isNumber', () => {
+  it('should return true for valid number values', () => {
+    expect(isNumber(0)).toBe(true)
+    expect(isNumber(123)).toBe(true)
+    expect(isNumber(-456)).toBe(true)
+    expect(isNumber(3.14)).toBe(true)
+    expect(isNumber(Infinity)).toBe(true)
+    expect(isNumber(-Infinity)).toBe(true)
+  })
+
+  it('should return false for NaN', () => {
+    expect(isNumber(NaN)).toBe(false)
+  })
+
+  it('should return false for non-number values', () => {
+    expect(isNumber('123')).toBe(false)
+    expect(isNumber(true)).toBe(false)
+    expect(isNumber(false)).toBe(false)
+    expect(isNumber(null)).toBe(false)
+    expect(isNumber(undefined)).toBe(false)
+    expect(isNumber([])).toBe(false)
+    expect(isNumber({})).toBe(false)
+    expect(isNumber(new Date())).toBe(false)
+  })
+})
diff --git a/packages/utilities/src/lib/ts-guards/is-number.ts b/packages/utilities/src/lib/ts-guards/is-number.ts
new file mode 100644
index 0000000..432eac2
--- /dev/null
+++ b/packages/utilities/src/lib/ts-guards/is-number.ts
@@ -0,0 +1,6 @@
+/**
+ * Checks if the provided value is a number. (NaN is technically a number, but this function returns false for NaN.)
+ */
+export function isNumber(value: unknown): value is number {
+  return typeof value === 'number' && !isNaN(value)
+}
diff --git a/packages/utilities/src/lib/ts-guards/is-string.spec.ts b/packages/utilities/src/lib/ts-guards/is-string.spec.ts
new file mode 100644
index 0000000..75d4787
--- /dev/null
+++ b/packages/utilities/src/lib/ts-guards/is-string.spec.ts
@@ -0,0 +1,21 @@
+import { isString } from './is-string.js'
+
+describe('isString', () => {
+  it('should return true for string values', () => {
+    expect(isString('')).toBe(true)
+    expect(isString('hello')).toBe(true)
+    expect(isString('123')).toBe(true)
+    expect(isString(' ')).toBe(true)
+  })
+
+  it('should return false for non-string values', () => {
+    expect(isString(123)).toBe(false)
+    expect(isString(true)).toBe(false)
+    expect(isString(false)).toBe(false)
+    expect(isString(null)).toBe(false)
+    expect(isString(undefined)).toBe(false)
+    expect(isString([])).toBe(false)
+    expect(isString({})).toBe(false)
+    expect(isString(new Date())).toBe(false)
+  })
+})
diff --git a/packages/utilities/src/lib/ts-guards/is-string.ts b/packages/utilities/src/lib/ts-guards/is-string.ts
new file mode 100644
index 0000000..3c257ba
--- /dev/null
+++ b/packages/utilities/src/lib/ts-guards/is-string.ts
@@ -0,0 +1,3 @@
+export function isString(value: unknown): value is string {
+  return typeof value === 'string'
+}