diff --git a/src/helper/CliUtils.ts b/src/helper/CliUtils.ts
index 389c0987..675436bb 100644
--- a/src/helper/CliUtils.ts
+++ b/src/helper/CliUtils.ts
@@ -2,6 +2,8 @@
  * Outputs the given JSON data.
  *
  * @param data - The data to be output.
+ *
+ * @internal
  */
 export function output(data: unknown): void {
 	// If data is string, output as is
diff --git a/src/helper/JsonUtils.ts b/src/helper/JsonUtils.ts
index b26d11a9..af9ac393 100644
--- a/src/helper/JsonUtils.ts
+++ b/src/helper/JsonUtils.ts
@@ -52,6 +52,8 @@ export function findByFilter<T>(data: NonNullable<unknown>, key: string, value:
  * @param data - The data on which search is to be performed.
  * @param value - The value to search.
  * @returns The key with the given value.
+ *
+ * @internal
  */
 export function findKeyByValue(data: NonNullable<unknown>, value: string): string | undefined {
 	// Finding the key-value pairs that have the given value
diff --git a/src/helper/StringUtils.ts b/src/helper/StringUtils.ts
deleted file mode 100644
index b9d4d8ac..00000000
--- a/src/helper/StringUtils.ts
+++ /dev/null
@@ -1,9 +0,0 @@
-/**
- * Converts the given API key to it's equivalent cookie string.
- *
- * @param apiKey - The API key representation of the cookie string.
- * @returns - The cookie string retrieved from the API key.
- */
-export function keyToCookie(apiKey: string): string {
-	return Buffer.from(apiKey, 'base64').toString('ascii');
-}
diff --git a/src/services/public/AuthService.ts b/src/services/public/AuthService.ts
index a6a8d01d..e8ae44d3 100644
--- a/src/services/public/AuthService.ts
+++ b/src/services/public/AuthService.ts
@@ -1,5 +1,6 @@
 import { Auth } from 'rettiwt-auth';
 
+import { EApiErrors } from '../../enums/Api';
 import { IRettiwtConfig } from '../../types/RettiwtConfig';
 
 import { FetcherService } from './FetcherService';
@@ -19,6 +20,55 @@ export class AuthService extends FetcherService {
 		super(config);
 	}
 
+	/**
+	 * Decodes the encoded cookie string.
+	 *
+	 * @param encodedCookies - The encoded cookie string to decode.
+	 * @returns The decoded cookie string.
+	 */
+	public static decodeCookie(encodedCookies: string): string {
+		// Decoding the encoded cookie string
+		const decodedCookies: string = Buffer.from(encodedCookies, 'base64').toString('ascii');
+
+		return decodedCookies;
+	}
+
+	/**
+	 * Encodes the given cookie string.
+	 *
+	 * @param cookieString - The cookie string to encode.
+	 * @returns The encoded cookie string.
+	 */
+	public static encodeCookie(cookieString: string): string {
+		// Encoding the cookie string to base64
+		const encodedCookies: string = Buffer.from(cookieString).toString('base64');
+
+		return encodedCookies;
+	}
+
+	/**
+	 * Gets the user's id from the given API key.
+	 *
+	 * @param apiKey - The API key.
+	 * @returns The user id associated with the API key.
+	 */
+	public static getUserId(apiKey: string): string {
+		// Getting the cookie string from the API key
+		const cookieString: string = AuthService.decodeCookie(apiKey);
+
+		// Searching for the user id in the cookie string
+		const searchResults: string[] | null = cookieString.match(/((?<=twid="u=)(.*)(?="))|((?<=twid=u%3D)(.*)(?=;))/);
+
+		// If user id was found
+		if (searchResults) {
+			return searchResults[0];
+		}
+		// If user id was not found
+		else {
+			throw new Error(EApiErrors.BAD_AUTHENTICATION);
+		}
+	}
+
 	/**
 	 * Login to twitter as guest.
 	 *
@@ -91,7 +141,7 @@ export class AuthService extends FetcherService {
 			).toHeader().cookie as string) ?? '';
 
 		// Converting the credentials to base64 string
-		apiKey = Buffer.from(apiKey).toString('base64');
+		apiKey = AuthService.encodeCookie(apiKey);
 
 		return apiKey;
 	}
diff --git a/src/services/public/FetcherService.ts b/src/services/public/FetcherService.ts
index b66acb9a..cbb10917 100644
--- a/src/services/public/FetcherService.ts
+++ b/src/services/public/FetcherService.ts
@@ -9,7 +9,6 @@ import { requests } from '../../collections/Requests';
 import { EApiErrors } from '../../enums/Api';
 import { ELogActions } from '../../enums/Logging';
 import { EResourceType } from '../../enums/Resource';
-import { keyToCookie } from '../../helper/StringUtils';
 import { FetchArgs } from '../../models/args/FetchArgs';
 import { PostArgs } from '../../models/args/PostArgs';
 import { IErrorHandler } from '../../types/ErrorHandler';
@@ -18,6 +17,8 @@ import { IRettiwtConfig } from '../../types/RettiwtConfig';
 import { ErrorService } from '../internal/ErrorService';
 import { LogService } from '../internal/LogService';
 
+import { AuthService } from './AuthService';
+
 /**
  * The base service that handles all HTTP requests.
  *
@@ -52,7 +53,7 @@ export class FetcherService {
 		LogService.enabled = config?.logging ?? false;
 		this.apiKey = config?.apiKey;
 		this.guestKey = config?.guestKey;
-		this.userId = config?.apiKey ? this.getUserId(config.apiKey) : undefined;
+		this.userId = config?.apiKey ? AuthService.getUserId(config.apiKey) : undefined;
 		this.authProxyUrl = config?.authProxyUrl ?? config?.proxyUrl;
 		this.proxyUrl = config?.proxyUrl;
 		this.timeout = config?.timeout ?? 0;
@@ -86,7 +87,7 @@ export class FetcherService {
 			// Logging
 			LogService.log(ELogActions.GET, { target: 'USER_CREDENTIAL' });
 
-			return new AuthCredential(keyToCookie(this.apiKey).split(';'));
+			return new AuthCredential(AuthService.decodeCookie(this.apiKey).split(';'));
 		} else if (this.guestKey) {
 			// Logging
 			LogService.log(ELogActions.GET, { target: 'GUEST_CREDENTIAL' });
@@ -121,29 +122,6 @@ export class FetcherService {
 		}
 	}
 
-	/**
-	 * Gets the authenticated user's id from the given API key.
-	 *
-	 * @param apiKey - The API key provided by the user.
-	 * @returns The user id associated with the API key.
-	 */
-	private getUserId(apiKey: string): string {
-		// Getting the cookie string from the API key
-		const cookieString: string = keyToCookie(apiKey);
-
-		// Searching for the user id in the cookie string
-		const searchResults: string[] | null = cookieString.match(/((?<=twid="u=)(.*)(?="))|((?<=twid=u%3D)(.*)(?=;))/);
-
-		// If user id was found
-		if (searchResults) {
-			return searchResults[0];
-		}
-		// If user id was not found
-		else {
-			throw new Error(EApiErrors.BAD_AUTHENTICATION);
-		}
-	}
-
 	/**
 	 * Validates the given args against the given resource.
 	 *