diff --git a/server.js b/server.js
index 137dd90..5c25908 100644
--- a/server.js
+++ b/server.js
@@ -1132,4 +1132,35 @@ app.post('/api/isLatLong', (req, res) => {
   res.json({ result });
 });
 
+/**
+ * POST /api/isDigit
+ * @summary Returns true if the input string contains only digits (0-9), otherwise false
+ * @description This endpoint validates if the input string consists exclusively of numeric digits.
+ * @param {BasicRequest} request.body.required - Request body containing the input string
+ * @return {BasicResponse} 200 - Success response
+ * @return {BadRequestResponse} 400 - Bad request response
+ * @example request - test
+ * {
+ *   "inputString": "123"
+ * }
+ * @example response - 200 - example payload
+ * {
+ *   "result": true
+ * }
+ * @example response - 400 - example
+ * {
+ *   "error": "Input string required as a parameter."
+ * }
+ */
+app.post('/api/isDigit', (req, res) => {
+  const { inputString } = req.body;
+
+  if (!inputString) {
+    return res.status(400).json({ error: requiredParameterResponse });
+  }
+
+  const result = ValidationFunctions.isDigit(inputString);
+  res.json({ result });
+});
+
 module.exports = app;
\ No newline at end of file
diff --git a/test/integration/isDigit.test.js b/test/integration/isDigit.test.js
new file mode 100644
index 0000000..7eabdde
--- /dev/null
+++ b/test/integration/isDigit.test.js
@@ -0,0 +1,123 @@
+const request = require('supertest');
+const app = require('../../server');
+
+describe('POST /api/isDigit', () => {
+  it('should return true for valid digit strings', async () => {
+    const response = await request(app)
+      .post('/api/isDigit')
+      .send({ inputString: '123' })
+      .expect(200);
+
+    expect(response.body.result).toBe(true);
+  });
+
+  it('should return true for single digit', async () => {
+    const response = await request(app)
+      .post('/api/isDigit')
+      .send({ inputString: '0' })
+      .expect(200);
+
+    expect(response.body.result).toBe(true);
+  });
+
+  it('should return true for multiple digits with leading zeros', async () => {
+    const response = await request(app)
+      .post('/api/isDigit')
+      .send({ inputString: '000123' })
+      .expect(200);
+
+    expect(response.body.result).toBe(true);
+  });
+
+  it('should return false for strings containing letters', async () => {
+    const response = await request(app)
+      .post('/api/isDigit')
+      .send({ inputString: '12a3' })
+      .expect(200);
+
+    expect(response.body.result).toBe(false);
+  });
+
+  it('should return false for strings containing special characters', async () => {
+    const response = await request(app)
+      .post('/api/isDigit')
+      .send({ inputString: '12.3' })
+      .expect(200);
+
+    expect(response.body.result).toBe(false);
+  });
+
+  it('should return true for strings with leading/trailing whitespace', async () => {
+    const response = await request(app)
+      .post('/api/isDigit')
+      .send({ inputString: ' 123 ' })
+      .expect(200);
+
+    expect(response.body.result).toBe(true);
+  });
+
+  it('should return false for strings with internal spaces', async () => {
+    const response = await request(app)
+      .post('/api/isDigit')
+      .send({ inputString: '12 3' })
+      .expect(200);
+
+    expect(response.body.result).toBe(false);
+  });
+
+  it('should return 400 for empty strings', async () => {
+    const response = await request(app)
+      .post('/api/isDigit')
+      .send({ inputString: '' })
+      .expect(400);
+  
+    expect(response.body.error).toBe('Input string required as a parameter.');
+  });
+  
+
+  it('should return false for negative numbers', async () => {
+    const response = await request(app)
+      .post('/api/isDigit')
+      .send({ inputString: '-123' })
+      .expect(200);
+
+    expect(response.body.result).toBe(false);
+  });
+
+  it('should return false for decimal numbers', async () => {
+    const response = await request(app)
+      .post('/api/isDigit')
+      .send({ inputString: '12.34' })
+      .expect(200);
+
+    expect(response.body.result).toBe(false);
+  });
+
+  it('should return 400 for missing inputString parameter', async () => {
+    const response = await request(app)
+      .post('/api/isDigit')
+      .send({})
+      .expect(400);
+
+    expect(response.body.error).toBe('Input string required as a parameter.');
+  });
+
+  it('should return 400 for null inputString parameter', async () => {
+    const response = await request(app)
+      .post('/api/isDigit')
+      .send({ inputString: null })
+      .expect(400);
+
+    expect(response.body.error).toBe('Input string required as a parameter.');
+  });
+
+  it('should return 400 for undefined inputString parameter', async () => {
+    const response = await request(app)
+      .post('/api/isDigit')
+      .send({ inputString: undefined })
+      .expect(400);
+
+    expect(response.body.error).toBe('Input string required as a parameter.');
+  });
+
+});
diff --git a/test/unit/isDigit.test.js b/test/unit/isDigit.test.js
new file mode 100644
index 0000000..d605939
--- /dev/null
+++ b/test/unit/isDigit.test.js
@@ -0,0 +1,71 @@
+const { isDigit } = require('../../validationFunctions');
+
+describe('isDigit', () => {
+  it('should return true for strings containing only digits', () => {
+    expect(isDigit('123')).toBe(true);
+    expect(isDigit('0')).toBe(true);
+    expect(isDigit('123456789')).toBe(true);
+    expect(isDigit('000123')).toBe(true);
+  });
+
+  it('should return false for strings containing letters', () => {
+    expect(isDigit('12a3')).toBe(false);
+    expect(isDigit('abc')).toBe(false);
+    expect(isDigit('123abc')).toBe(false);
+    expect(isDigit('abc123')).toBe(false);
+  });
+
+  it('should return false for strings containing special characters', () => {
+    expect(isDigit('12.3')).toBe(false);
+    expect(isDigit('12-3')).toBe(false);
+    expect(isDigit('12_3')).toBe(false);
+    expect(isDigit('12@3')).toBe(false);
+    expect(isDigit('12#3')).toBe(false);
+  });
+
+  it('should allow leading/trailing spaces but fail on internal spaces', () => {
+    expect(isDigit(' 123')).toBe(true);
+    expect(isDigit('123 ')).toBe(true);
+    expect(isDigit(' 123 ')).toBe(true);
+    expect(isDigit('12 3')).toBe(false);
+  });
+
+  it('should return false for empty strings', () => {
+    expect(isDigit('')).toBe(false);
+  });
+
+  it('should return false for null and undefined', () => {
+    expect(isDigit(null)).toBe(false);
+    expect(isDigit(undefined)).toBe(false);
+  });
+
+  it('should return false for non-string inputs', () => {
+    expect(isDigit(true)).toBe(false);
+    expect(isDigit(false)).toBe(false);
+    expect(isDigit({})).toBe(false);
+    expect(isDigit([])).toBe(false);
+  });
+
+  it('should return true for strings with leading and trailing whitespace', () => {
+    expect(isDigit('  123  ')).toBe(true);
+    expect(isDigit('\t123\n')).toBe(true);
+    expect(isDigit('\r123\f')).toBe(true);
+  });
+
+  it('should return false for decimal numbers', () => {
+    expect(isDigit('12.34')).toBe(false);
+    expect(isDigit('.123')).toBe(false);
+    expect(isDigit('123.')).toBe(false);
+  });
+
+  it('should return false for negative numbers', () => {
+    expect(isDigit('-123')).toBe(false);
+    expect(isDigit('-0')).toBe(false);
+  });
+
+  it('should return false for hexadecimal strings', () => {
+    expect(isDigit('1A2B3C')).toBe(false);
+    expect(isDigit('0xFF')).toBe(false);
+    expect(isDigit('1a2b3c')).toBe(false);
+  });
+});
diff --git a/validationFunctions.js b/validationFunctions.js
index 94157ad..33aa1d1 100644
--- a/validationFunctions.js
+++ b/validationFunctions.js
@@ -476,6 +476,31 @@ module.exports = class ValidationFunctions {
     const decimalDegreesRegex = /^-?\d{1,3}(?:\.\d+)?,\s*-?\d{1,3}(?:\.\d+)?$/;
     return decimalDegreesRegex.test(trimmedInput);
   }
+
+  /**
+   * Checks if the given string contains only digit characters (0-9).
+   * 
+   * This function validates that the input string consists exclusively of numeric digits.
+   * It returns false for empty strings, null, undefined, or strings containing any non-digit characters.
+   * 
+   * @param {string} inputString - The string to validate.
+   * @returns {boolean} - Returns `true` if `inputString` contains only digits, otherwise `false`.
+   * 
+   * @example
+   * isDigit("123"); // Returns: true
+   * isDigit("0"); // Returns: true
+   * isDigit("12a3"); // Returns: false
+   * isDigit("12.3"); // Returns: false
+   * isDigit(""); // Returns: false
+   * isDigit("abc"); // Returns: false
+   */
+  static isDigit(inputString) {
+    if (!inputString || typeof inputString !== "string") return false;
+    
+    const trimmedInput = inputString.trim();
+    const digitRegex = /^[0-9]+$/;
+    return digitRegex.test(trimmedInput);
+  }
 }
 
 const handleAxiosError = (error) => {