diff --git a/assets/locales/en/common.json b/assets/locales/en/common.json
index edcafa1da..dcb97ec0b 100644
--- a/assets/locales/en/common.json
+++ b/assets/locales/en/common.json
@@ -13,7 +13,11 @@
 		"BASE_TYPE_CONSTANT": "This field must be {{value}}",
 		"EMAIL_TYPE_INVALID_EMAIL": "Not a well-formed email address",
 		"DATE_TYPE_PARSE": "Could not parse {{date}}. Should be ISO8601",
-		"BASE_TYPE_BAD_LENGTH": "Must be between {{length}} in length"
+		"BASE_TYPE_BAD_LENGTH": "Must be between {{length}} in length",
+		"PASSWORD_DOES_NOT_MATCH": "Password does not match.",
+		"DISCRIMINATOR_UPDATE_BLOCKED": "This discriminator cannot be updated",
+		"USERNAME_ALREADY_TAKEN": "Username is unavailable. Try adding numbers, letters, underscores _ , or periods.",
+		"INVALID_DISCRIMINATOR": "This discriminator is already in use."
 	},
 	"body": {
 		"INVALID_BODY": "Invalid Body",
diff --git a/assets/locales/ur/auth.json b/assets/locales/ur/auth.json
index 1dac24744..93631abcf 100644
--- a/assets/locales/ur/auth.json
+++ b/assets/locales/ur/auth.json
@@ -10,8 +10,8 @@
 		"EMAIL_INVALID": "Invalid Email",
 		"EMAIL_ALREADY_REGISTERED": "Email is already registered",
 		"DATE_OF_BIRTH_UNDERAGE": "You need to be {{years}} years or older",
-                "PASSWORD_REQUIREMENTS_MIN_LENGTH": "Must be at least {{min}} characters long.",
-                "CONSENT_REQUIRED": "You must agree to the Terms of Service and Privacy Policy.",
+		"PASSWORD_REQUIREMENTS_MIN_LENGTH": "Must be at least {{min}} characters long.",
+		"CONSENT_REQUIRED": "You must agree to the Terms of Service and Privacy Policy.",
 		"USERNAME_TOO_MANY_USERS": "Too many users have this username, please try another"
 	}
 }
diff --git a/assets/openapi.json b/assets/openapi.json
index 4c9006c29..7b2243e9c 100644
Binary files a/assets/openapi.json and b/assets/openapi.json differ
diff --git a/assets/schemas.json b/assets/schemas.json
index 9a00e6132..0f2602f71 100644
Binary files a/assets/schemas.json and b/assets/schemas.json differ
diff --git a/src/api/routes/users/@me/index.ts b/src/api/routes/users/@me/index.ts
index fc44e17e9..f4578126c 100644
--- a/src/api/routes/users/@me/index.ts
+++ b/src/api/routes/users/@me/index.ts
@@ -70,6 +70,8 @@ router.patch(
 	}),
 	async (req: Request, res: Response) => {
 		const body = req.body as UserModifySchema;
+		const { uniqueUsernames } = Config.get().general;
+		const { minUsername, maxUsername } = Config.get().limits.user;
 
 		const user = await User.findOneOrFail({
 			where: { id: req.user_id },
@@ -140,8 +142,52 @@ router.patch(
 			newToken = (await generateToken(user.id)) as string;
 		}
 
-		// TODO: uniqueUsernames: disallow if uniqueUsernames is enabled
 		if (body.username) {
+			// password is required to update username
+			if (!body.password)
+				throw FieldErrors({
+					password: {
+						message: req.t("common:field.PASSWORD_DOES_NOT_MATCH"),
+						code: "PASSWORD_DOES_NOT_MATCH",
+					},
+				});
+
+			// handle username changes (pomelo)
+			if (uniqueUsernames) {
+				body.username = body.username.toLowerCase();
+				// validate username length
+				if (
+					body.username.length < minUsername ||
+					body.username.length > maxUsername
+				) {
+					throw FieldErrors({
+						username: {
+							code: "BASE_TYPE_BAD_LENGTH",
+							message: req.t(
+								"common:field.BASE_TYPE_BAD_LENGTH",
+								{ length: `${minUsername} and ${maxUsername}` },
+							),
+						},
+					});
+				}
+
+				// check if username is already taken (pomelo only)
+				const userCount = await User.count({
+					where: { username: body.username },
+				});
+				if (userCount > 0) {
+					throw FieldErrors({
+						username: {
+							code: "USERNAME_ALREADY_TAKEN",
+							message: req.t(
+								"common:field.USERNAME_ALREADY_TAKEN",
+							),
+						},
+					});
+				}
+			}
+
+			// handle username changes (old username system)
 			const check_username = body?.username?.replace(/\s/g, "");
 			if (!check_username) {
 				throw FieldErrors({
@@ -152,7 +198,6 @@ router.patch(
 				});
 			}
 
-			const { maxUsername } = Config.get().limits.user;
 			if (check_username.length > maxUsername) {
 				throw FieldErrors({
 					username: {
@@ -163,8 +208,18 @@ router.patch(
 			}
 		}
 
-		// TODO: uniqueUsernames: disallow if uniqueUsernames is enabled
 		if (body.discriminator) {
+			if (uniqueUsernames) {
+				throw FieldErrors({
+					username: {
+						code: "DISCRIMINATOR_UPDATE_BLOCKED",
+						message: req.t(
+							"common:field.DISCRIMINATOR_UPDATE_BLOCKED",
+						),
+					},
+				});
+			}
+
 			if (
 				await User.findOne({
 					where: {
@@ -176,7 +231,7 @@ router.patch(
 				throw FieldErrors({
 					discriminator: {
 						code: "INVALID_DISCRIMINATOR",
-						message: "This discriminator is already in use.",
+						message: req.t("common.field.INVALID_DISCRIMINATOR"),
 					},
 				});
 			}
diff --git a/src/util/config/types/subconfigurations/limits/UserLimits.ts b/src/util/config/types/subconfigurations/limits/UserLimits.ts
index 8f9b1a97f..77092344c 100644
--- a/src/util/config/types/subconfigurations/limits/UserLimits.ts
+++ b/src/util/config/types/subconfigurations/limits/UserLimits.ts
@@ -18,6 +18,7 @@
 
 export class UserLimits {
 	maxGuilds: number = 1048576;
+	minUsername: number = 2;
 	maxUsername: number = 32;
 	maxFriends: number = 5000;
 }
diff --git a/src/util/entities/User.ts b/src/util/entities/User.ts
index acd2ea748..d1fbb5c2b 100644
--- a/src/util/entities/User.ts
+++ b/src/util/entities/User.ts
@@ -38,7 +38,6 @@ import { UserSettings } from "./UserSettings";
 export enum PublicUserEnum {
 	username,
 	global_name,
-	legacy_username,
 	discriminator,
 	id,
 	public_flags,
@@ -241,7 +240,7 @@ export class User extends BaseClass {
 
 	// TODO: I don't like this method?
 	validate() {
-		if (this.discriminator) {
+		if (this.discriminator && this.discriminator !== "0") {
 			const discrim = Number(this.discriminator);
 			if (
 				isNaN(discrim) ||
@@ -334,9 +333,8 @@ export class User extends BaseClass {
 	public get tag(): string {
 		const { uniqueUsernames } = Config.get().general;
 
-		// if uniqueUsernames is enabled, global_name should be set
 		return uniqueUsernames
-			? (this.global_name as string)
+			? this.username
 			: `${this.username}#${this.discriminator}`;
 	}
 
@@ -387,7 +385,7 @@ export class User extends BaseClass {
 		});
 
 		const user = User.create({
-			username: username,
+			username: uniqueUsernames ? username.toLowerCase() : username,
 			discriminator,
 			id: id || Snowflake.generate(),
 			email: email,
@@ -397,7 +395,6 @@ export class User extends BaseClass {
 			},
 			extended_settings: "{}",
 			settings: settings,
-
 			premium_since: Config.get().defaults.user.premium
 				? new Date()
 				: undefined,
diff --git a/src/util/schemas/UserModifySchema.ts b/src/util/schemas/UserModifySchema.ts
index e155b9af4..72d15dcb6 100644
--- a/src/util/schemas/UserModifySchema.ts
+++ b/src/util/schemas/UserModifySchema.ts
@@ -38,4 +38,5 @@ export interface UserModifySchema {
 	 * @maxLength 4
 	 */
 	discriminator?: string;
+	global_name?: string;
 }