diff --git a/packages/better-auth/src/api/rate-limiter/rate-limiter.test.ts b/packages/better-auth/src/api/rate-limiter/rate-limiter.test.ts
index 911da7e351..0f678fabe5 100644
--- a/packages/better-auth/src/api/rate-limiter/rate-limiter.test.ts
+++ b/packages/better-auth/src/api/rate-limiter/rate-limiter.test.ts
@@ -336,7 +336,7 @@ describe("IPv6 address normalization and rate limiting", () => {
 
 		// All should normalize to the same value
 		expect(uniqueValues.size).toBe(1);
-		expect(normalized[0]).toBe("2001:0db8:0000:0000:0000:0000:0000:0001");
+		expect(normalized[0]).toBe("2001:0db8:0000:0000:0000:0000:0000:0000");
 	});
 
 	it("should convert IPv4-mapped IPv6 to IPv4", () => {
@@ -393,12 +393,12 @@ describe("IPv6 address normalization and rate limiting", () => {
 	});
 
 	it("should handle localhost IPv6 addresses", () => {
-		expect(normalizeIP("::1")).toBe("0000:0000:0000:0000:0000:0000:0000:0001");
+		expect(normalizeIP("::1")).toBe("0000:0000:0000:0000:0000:0000:0000:0000");
 	});
 
 	it("should handle link-local IPv6 addresses", () => {
 		const linkLocal = normalizeIP("fe80::1");
-		expect(linkLocal).toBe("fe80:0000:0000:0000:0000:0000:0000:0001");
+		expect(linkLocal).toBe("fe80:0000:0000:0000:0000:0000:0000:0000");
 	});
 
 	it("IPv6 subnet should not affect IPv4 addresses", () => {
diff --git a/packages/core/src/types/init-options.ts b/packages/core/src/types/init-options.ts
index 42c7e1bb1b..8dcd8d8af5 100644
--- a/packages/core/src/types/init-options.ts
+++ b/packages/core/src/types/init-options.ts
@@ -158,7 +158,7 @@ export type BetterAuthAdvancedOptions = {
 				 * Note: This only affects IPv6 addresses. IPv4 addresses are always
 				 * rate limited individually.
 				 *
-				 * @default 128 (individual address)
+				 * @default 64 (/64 subnet)
 				 */
 				ipv6Subnet?: 128 | 64 | 48 | 32 | undefined;
 		  }
diff --git a/packages/core/src/utils/ip.test.ts b/packages/core/src/utils/ip.test.ts
index 191a51ec29..bcf70d740b 100644
--- a/packages/core/src/utils/ip.test.ts
+++ b/packages/core/src/utils/ip.test.ts
@@ -34,20 +34,22 @@ describe("IP Normalization", () => {
 
 	describe("IPv6 Normalization", () => {
 		it("should normalize compressed IPv6 to full form", () => {
-			expect(normalizeIP("2001:db8::1")).toBe(
+			expect(normalizeIP("2001:db8::1", { ipv6Subnet: 128 })).toBe(
 				"2001:0db8:0000:0000:0000:0000:0000:0001",
 			);
-			expect(normalizeIP("::1")).toBe(
+			expect(normalizeIP("::1", { ipv6Subnet: 128 })).toBe(
 				"0000:0000:0000:0000:0000:0000:0000:0001",
 			);
-			expect(normalizeIP("::")).toBe("0000:0000:0000:0000:0000:0000:0000:0000");
+			expect(normalizeIP("::", { ipv6Subnet: 128 })).toBe(
+				"0000:0000:0000:0000:0000:0000:0000:0000",
+			);
 		});
 
 		it("should normalize uppercase to lowercase", () => {
-			expect(normalizeIP("2001:DB8::1")).toBe(
+			expect(normalizeIP("2001:DB8::1", { ipv6Subnet: 128 })).toBe(
 				"2001:0db8:0000:0000:0000:0000:0000:0001",
 			);
-			expect(normalizeIP("2001:0DB8:ABCD:EF00::1")).toBe(
+			expect(normalizeIP("2001:0DB8:ABCD:EF00::1", { ipv6Subnet: 128 })).toBe(
 				"2001:0db8:abcd:ef00:0000:0000:0000:0001",
 			);
 		});
@@ -55,16 +57,22 @@ describe("IP Normalization", () => {
 		it("should handle various IPv6 formats consistently", () => {
 			// All these represent the same address
 			const normalized = "2001:0db8:0000:0000:0000:0000:0000:0001";
-			expect(normalizeIP("2001:db8::1")).toBe(normalized);
-			expect(normalizeIP("2001:0db8:0:0:0:0:0:1")).toBe(normalized);
-			expect(normalizeIP("2001:db8:0::1")).toBe(normalized);
-			expect(normalizeIP("2001:0db8::0:0:0:1")).toBe(normalized);
+			expect(normalizeIP("2001:db8::1", { ipv6Subnet: 128 })).toBe(normalized);
+			expect(normalizeIP("2001:0db8:0:0:0:0:0:1", { ipv6Subnet: 128 })).toBe(
+				normalized,
+			);
+			expect(normalizeIP("2001:db8:0::1", { ipv6Subnet: 128 })).toBe(
+				normalized,
+			);
+			expect(normalizeIP("2001:0db8::0:0:0:1", { ipv6Subnet: 128 })).toBe(
+				normalized,
+			);
 		});
 
 		it("should handle IPv6 with :: at different positions", () => {
-			expect(normalizeIP("2001:db8:85a3::8a2e:370:7334")).toBe(
-				"2001:0db8:85a3:0000:0000:8a2e:0370:7334",
-			);
+			expect(
+				normalizeIP("2001:db8:85a3::8a2e:370:7334", { ipv6Subnet: 128 }),
+			).toBe("2001:0db8:85a3:0000:0000:8a2e:0370:7334");
 			expect(normalizeIP("::ffff:192.0.2.1")).not.toContain("::");
 		});
 	});
@@ -131,11 +139,11 @@ describe("IP Normalization", () => {
 			expect(ip1).toBe(ip2);
 		});
 
-		it("should handle /128 (full address) by default", () => {
+		it("should handle /64 subnet by default", () => {
 			const ip1 = normalizeIP("2001:db8::1");
-			const ip2 = normalizeIP("2001:db8::1", { ipv6Subnet: 128 });
+			const ip2 = normalizeIP("2001:db8::1", { ipv6Subnet: 64 });
 			expect(ip1).toBe(ip2);
-			expect(ip1).toBe("2001:0db8:0000:0000:0000:0000:0000:0001");
+			expect(ip1).toBe("2001:0db8:0000:0000:0000:0000:0000:0000");
 		});
 
 		it("should not affect IPv4 addresses when ipv6Subnet is set", () => {
@@ -179,7 +187,9 @@ describe("IP Normalization", () => {
 				"2001:db8::0:1",
 			];
 
-			const normalized = representations.map((ip) => normalizeIP(ip));
+			const normalized = representations.map((ip) =>
+				normalizeIP(ip, { ipv6Subnet: 128 }),
+			);
 			// All should normalize to the same value
 			const uniqueValues = new Set(normalized);
 			expect(uniqueValues.size).toBe(1);
@@ -223,19 +233,21 @@ describe("IP Normalization", () => {
 	describe("Edge Cases", () => {
 		it("should handle localhost addresses", () => {
 			expect(normalizeIP("127.0.0.1")).toBe("127.0.0.1");
-			expect(normalizeIP("::1")).toBe(
+			expect(normalizeIP("::1", { ipv6Subnet: 128 })).toBe(
 				"0000:0000:0000:0000:0000:0000:0000:0001",
 			);
 		});
 
 		it("should handle all-zeros address", () => {
 			expect(normalizeIP("0.0.0.0")).toBe("0.0.0.0");
-			expect(normalizeIP("::")).toBe("0000:0000:0000:0000:0000:0000:0000:0000");
+			expect(normalizeIP("::", { ipv6Subnet: 128 })).toBe(
+				"0000:0000:0000:0000:0000:0000:0000:0000",
+			);
 		});
 
 		it("should handle link-local addresses", () => {
 			expect(normalizeIP("169.254.0.1")).toBe("169.254.0.1");
-			expect(normalizeIP("fe80::1")).toBe(
+			expect(normalizeIP("fe80::1", { ipv6Subnet: 128 })).toBe(
 				"fe80:0000:0000:0000:0000:0000:0000:0001",
 			);
 		});
diff --git a/packages/core/src/utils/ip.ts b/packages/core/src/utils/ip.ts
index 4f2ac230bf..4134f45534 100644
--- a/packages/core/src/utils/ip.ts
+++ b/packages/core/src/utils/ip.ts
@@ -160,7 +160,7 @@ function normalizeIPv6(
  *
  * @example
  * normalizeIP("2001:DB8::1")
- * // -> "2001:0db8:0000:0000:0000:0000:0000:0001"
+ * // -> "2001:0db8:0000:0000:0000:0000:0000:0000"
  *
  * @example
  * normalizeIP("::ffff:192.0.2.1")
@@ -192,7 +192,7 @@ export function normalizeIP(
 	}
 
 	// Normalize IPv6
-	const subnetPrefix = options.ipv6Subnet || 128;
+	const subnetPrefix = options.ipv6Subnet || 64;
 	return normalizeIPv6(ip, subnetPrefix);
 }