diff --git a/Timestamp48/benchmark.js b/Timestamp48/benchmark.js
new file mode 100644
index 0000000..4377d8d
--- /dev/null
+++ b/Timestamp48/benchmark.js
@@ -0,0 +1,67 @@
+'use strict';
+
+const original = require('./gpt-5.js');
+const optimized = require('./optimized.js');
+
+const benchmark = (name, fn, iterations) => {
+  // Warmup
+  for (let i = 0; i < 1000; i++) fn();
+
+  // Actual benchmark
+  const start = process.hrtime.bigint();
+  for (let i = 0; i < iterations; i++) {
+    fn();
+  }
+  const end = process.hrtime.bigint();
+
+  const timeMs = Number(end - start) / 1e6;
+  const opsPerSec = (iterations / timeMs) * 1000;
+
+  console.log(`${name}:`);
+  console.log(`  Time: ${timeMs.toFixed(2)}ms`);
+  console.log(`  Ops/sec: ${opsPerSec.toFixed(0)}`);
+  const avgTime = ((timeMs / iterations) * 1000).toFixed(3);
+  console.log(`  Avg time per op: ${avgTime}μs`);
+
+  return { timeMs, opsPerSec };
+};
+
+const iterations = 100000;
+
+console.log(`\nBenchmark: ${iterations} UUID generations\n`);
+console.log('='.repeat(50));
+
+const originalResult = benchmark(
+  'Original (gpt-5.js)',
+  () => original.generateV7Base64Url(),
+  iterations,
+);
+
+console.log('');
+
+const optimizedResult = benchmark(
+  'Optimized',
+  () => optimized.generateV7Base64Url(),
+  iterations,
+);
+
+console.log('');
+
+const batchResult = benchmark(
+  'Batch (10 at once)',
+  () => optimized.generateBatch(10),
+  iterations / 10,
+);
+
+console.log('\n' + '='.repeat(50));
+console.log('\nSummary:');
+const perfGain = (
+  (optimizedResult.opsPerSec / originalResult.opsPerSec - 1) *
+  100
+).toFixed(1);
+console.log(`  Performance gain: ${perfGain}%`);
+const batchEff = (
+  ((batchResult.opsPerSec * 10) / optimizedResult.opsPerSec - 1) *
+  100
+).toFixed(1);
+console.log(`  Batch efficiency: ${batchEff}% faster per UUID`);
diff --git a/Timestamp48/optimized.js b/Timestamp48/optimized.js
new file mode 100644
index 0000000..aa709e5
--- /dev/null
+++ b/Timestamp48/optimized.js
@@ -0,0 +1,97 @@
+'use strict';
+
+const crypto = require('crypto');
+
+// Constants for better readability
+const VERSION_7 = 0x70;
+const VARIANT_RFC4122 = 0x80;
+const VARIANT_MASK = 0x3f;
+const SEQ_MAX = 0x0fff;
+
+// Pre-allocated buffers for better performance
+const sharedBuffer = Buffer.allocUnsafe(16);
+const randomPool = Buffer.allocUnsafe(1024);
+let poolOffset = 1024;
+
+// State management
+const state = {
+  lastTimestamp: 0n,
+  sequence: 0,
+};
+
+// Get random bytes from pre-allocated pool
+const getRandomBytes = (length) => {
+  if (poolOffset + length > randomPool.length) {
+    crypto.randomFillSync(randomPool);
+    poolOffset = 0;
+  }
+  const result = randomPool.subarray(poolOffset, poolOffset + length);
+  poolOffset += length;
+  return result;
+};
+
+// Get current timestamp in milliseconds
+const getCurrentTimestamp = () => BigInt(Date.now());
+
+// Pack UUID v7 components into buffer
+const packUuidV7 = (timestamp, sequence, randomTail) => {
+  // Write 48-bit timestamp (big-endian)
+  sharedBuffer.writeBigUInt64BE(timestamp << 16n, 0);
+
+  // Version (7) and sequence high bits
+  sharedBuffer[6] = VERSION_7 | ((sequence >> 8) & 0x0f);
+  sharedBuffer[7] = sequence & 0xff;
+
+  // RFC 4122 variant and random tail
+  randomTail.copy(sharedBuffer, 8);
+  sharedBuffer[8] = (sharedBuffer[8] & VARIANT_MASK) | VARIANT_RFC4122;
+
+  return sharedBuffer;
+};
+
+/**
+ * Generates a UUIDv7-like identifier with improved performance
+ * @returns {string} Base64URL encoded 22-character string
+ */
+const generateV7Base64Url = () => {
+  let timestamp = getCurrentTimestamp();
+
+  // Handle sequence for monotonicity and counter overflow
+  if (timestamp <= state.lastTimestamp) {
+    timestamp = state.lastTimestamp;
+    state.sequence = (state.sequence + 1) & SEQ_MAX;
+    if (state.sequence === 0) {
+      // Sequence overflow, increment timestamp.
+      // This is a robust way to handle high generation rates
+      // without busy-waiting for the next millisecond.
+      timestamp++;
+      state.lastTimestamp = timestamp;
+    }
+  } else {
+    // New millisecond or time moved backwards: randomize sequence
+    state.lastTimestamp = timestamp;
+    // Using random bytes is faster than crypto.randomInt()
+    state.sequence = getRandomBytes(2).readUInt16BE(0) & SEQ_MAX;
+  }
+
+  // Get random tail from pool
+  const randomTail = getRandomBytes(8);
+
+  // Pack and encode
+  const packed = packUuidV7(timestamp, state.sequence, randomTail);
+  return packed.toString('base64url');
+};
+
+// Batch generation for better performance
+const generateBatch = (count) => {
+  const results = new Array(count);
+  for (let i = 0; i < count; i++) {
+    results[i] = generateV7Base64Url();
+  }
+  return results;
+};
+
+module.exports = {
+  generateV7Base64Url,
+  generateBatch,
+};
diff --git a/Timestamp48/optimized.mjs b/Timestamp48/optimized.mjs
new file mode 100644
index 0000000..842e5a0
--- /dev/null
+++ b/Timestamp48/optimized.mjs
@@ -0,0 +1,130 @@
+// optimized.mjs - ESM browser-safe version with performance improvements
+
+// Constants
+const VERSION_7 = 0x70;
+const VARIANT_RFC4122 = 0x80;
+const VARIANT_MASK = 0x3f;
+const SEQ_MAX = 0x0fff;
+const BASE64_CHARS =
+  'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_';
+
+// Pre-allocated typed arrays for better performance
+const sharedBytes = new Uint8Array(16);
+const randomPool = new Uint8Array(1024);
+let poolOffset = 1024;
+
+// State management
+const state = {
+  lastTimestamp: 0n,
+  sequence: 0,
+};
+
+// Optimized Base64URL encoding
+const encodeBase64Url = (bytes) => {
+  let result = '';
+  let i = 0;
+
+  // Process 3 bytes at a time
+  while (i < 15) {
+    const b1 = bytes[i++];
+    const b2 = bytes[i++];
+    const b3 = bytes[i++];
+
+    result += BASE64_CHARS[b1 >> 2];
+    result += BASE64_CHARS[((b1 & 3) << 4) | (b2 >> 4)];
+    result += BASE64_CHARS[((b2 & 15) << 2) | (b3 >> 6)];
+    result += BASE64_CHARS[b3 & 63];
+  }
+
+  // Handle last byte
+  const lastByte = bytes[15];
+  result += BASE64_CHARS[lastByte >> 2];
+  result += BASE64_CHARS[(lastByte & 3) << 4];
+
+  return result;
+};
+
+// Get random bytes from pre-allocated pool
+const getRandomBytes = (length) => {
+  if (poolOffset + length > randomPool.length) {
+    globalThis.crypto.getRandomValues(randomPool);
+    poolOffset = 0;
+  }
+  const result = randomPool.subarray(poolOffset, poolOffset + length);
+  poolOffset += length;
+  return result;
+};
+
+// Get random 12-bit sequence
+const getRandomSequence = () => {
+  const bytes = getRandomBytes(2);
+  return ((bytes[0] << 8) | bytes[1]) & SEQ_MAX;
+};
+
+// Get current timestamp
+const getCurrentTimestamp = () => BigInt(Date.now());
+
+// Pack UUID v7 components
+const packUuidV7 = (timestamp, sequence, randomTail) => {
+  // Write 48-bit timestamp (big-endian)
+  sharedBytes[0] = Number((timestamp >> 40n) & 0xffn);
+  sharedBytes[1] = Number((timestamp >> 32n) & 0xffn);
+  sharedBytes[2] = Number((timestamp >> 24n) & 0xffn);
+  sharedBytes[3] = Number((timestamp >> 16n) & 0xffn);
+  sharedBytes[4] = Number((timestamp >> 8n) & 0xffn);
+  sharedBytes[5] = Number(timestamp & 0xffn);
+
+  // Version and sequence
+  sharedBytes[6] = VERSION_7 | ((sequence >> 8) & 0x0f);
+  sharedBytes[7] = sequence & 0xff;
+
+  // Copy random tail and apply variant
+  sharedBytes.set(randomTail, 8);
+  sharedBytes[8] = (sharedBytes[8] & VARIANT_MASK) | VARIANT_RFC4122;
+
+  return sharedBytes;
+};
+
+/**
+ * Generates a UUIDv7-like identifier optimized for browser performance
+ * @returns {string} Base64URL encoded 22-character string
+ */
+export const generateV7Base64Url = () => {
+  const now = getCurrentTimestamp();
+  let timestamp = now > state.lastTimestamp ? now : state.lastTimestamp;
+
+  // Handle sequence for monotonicity
+  if (timestamp === state.lastTimestamp) {
+    state.sequence = (state.sequence + 1) & SEQ_MAX;
+    if (state.sequence === 0) {
+      // Virtual timestamp increment to avoid blocking
+      timestamp = state.lastTimestamp + 1n;
+    }
+  } else {
+    state.sequence = getRandomSequence();
+  }
+
+  state.lastTimestamp = timestamp;
+
+  // Get random tail from pool
+  const randomTail = getRandomBytes(8);
+
+  // Pack and encode
+  packUuidV7(timestamp, state.sequence, randomTail);
+  return encodeBase64Url(sharedBytes);
+};
+
+/**
+ * Generate batch of UUIDs for better performance
+ * @param {number} count - Number of UUIDs to generate
+ * @returns {Array<string>} Array of Base64URL encoded UUIDs
+ */
+export const generateBatch = (count) => {
+  const results = new Array(count);
+  for (let i = 0; i < count; i++) {
+    results[i] = generateV7Base64Url();
+  }
+  return results;
+};
+
+export default generateV7Base64Url;
diff --git a/Timestamp48/test.js b/Timestamp48/test.js
new file mode 100644
index 0000000..cf75f13
--- /dev/null
+++ b/Timestamp48/test.js
@@ -0,0 +1,80 @@
+'use strict';
+
+const { test } = require('node:test');
+const assert = require('node:assert');
+const original = require('./gpt-5.js');
+const optimized = require('./optimized.js');
+
+test('UUID format validation', () => {
+  const uuid1 = original.generateV7Base64Url();
+  const uuid2 = optimized.generateV7Base64Url();
+
+  // Check length (22 chars for Base64URL without padding)
+  assert.strictEqual(uuid1.length, 22);
+  assert.strictEqual(uuid2.length, 22);
+
+  // Check Base64URL characters
+  const base64UrlPattern = /^[A-Za-z0-9\-_]+$/;
+  assert.match(uuid1, base64UrlPattern);
+  assert.match(uuid2, base64UrlPattern);
+});
+
+test('Monotonicity within same millisecond', () => {
+  const uuids = [];
+  for (let i = 0; i < 100; i++) {
+    uuids.push(optimized.generateV7Base64Url());
+  }
+
+  // Check that UUIDs are unique
+  const uniqueUuids = new Set(uuids);
+  assert.strictEqual(uniqueUuids.size, uuids.length);
+});
+
+test('Batch generation', () => {
+  const batch = optimized.generateBatch(10);
+
+  assert.strictEqual(batch.length, 10);
+
+  // Check all are unique
+  const uniqueBatch = new Set(batch);
+  assert.strictEqual(uniqueBatch.size, batch.length);
+
+  // Check format
+  batch.forEach((uuid) => {
+    assert.strictEqual(uuid.length, 22);
+    assert.match(uuid, /^[A-Za-z0-9\-_]+$/);
+  });
+});
+
+test('Performance comparison', () => {
+  const iterations = 10000;
+
+  // Test original version
+  const startOriginal = process.hrtime.bigint();
+  for (let i = 0; i < iterations; i++) {
+    original.generateV7Base64Url();
+  }
+  const endOriginal = process.hrtime.bigint();
+  // Convert to ms
+  const timeOriginal = Number(endOriginal - startOriginal) / 1e6;
+
+  // Test optimized version
+  const startOptimized = process.hrtime.bigint();
+  for (let i = 0; i < iterations; i++) {
+    optimized.generateV7Base64Url();
+  }
+  const endOptimized = process.hrtime.bigint();
+  const timeOptimized = Number(endOptimized - startOptimized) / 1e6;
+
+  console.log(`\nPerformance Results (${iterations} iterations):`);
+  console.log(`Original: ${timeOriginal.toFixed(2)}ms`);
+  console.log(`Optimized: ${timeOptimized.toFixed(2)}ms`);
+  const improvement = ((1 - timeOptimized / timeOriginal) * 100).toFixed(1);
+  console.log(`Improvement: ${improvement}%`);
+
+  // Optimized should be at least as fast
+  assert.ok(
+    timeOptimized <= timeOriginal * 1.1,
+    'Optimized version should not be slower',
+  );
+});