diff --git a/src/tools/index.ts b/src/tools/index.ts
index 388cfaf4..1e18ce47 100644
--- a/src/tools/index.ts
+++ b/src/tools/index.ts
@@ -45,6 +45,7 @@ import { tool as htmlWysiwygEditor } from './html-wysiwyg-editor';
 import { tool as rsaKeyPairGenerator } from './rsa-key-pair-generator';
 import { tool as textToNatoAlphabet } from './text-to-nato-alphabet';
 import { tool as slugifyString } from './slugify-string';
+import { tool as snowflakeIdDecoder } from './snowflake-id-decoder';
 import { tool as keycodeInfo } from './keycode-info';
 import { tool as jsonMinify } from './json-minify';
 import { tool as bcrypt } from './bcrypt';
@@ -91,7 +92,7 @@ import { tool as yamlViewer } from './yaml-viewer';
 export const toolsByCategory: ToolCategory[] = [
   {
     name: 'Crypto',
-    components: [tokenGenerator, hashText, bcrypt, uuidGenerator, ulidGenerator, cypher, bip39, hmacGenerator, rsaKeyPairGenerator, passwordStrengthAnalyser, pdfSignatureChecker],
+    components: [snowflakeIdDecoder, tokenGenerator, hashText, bcrypt, uuidGenerator, ulidGenerator, cypher, bip39, hmacGenerator, rsaKeyPairGenerator, passwordStrengthAnalyser, pdfSignatureChecker],
   },
   {
     name: 'Converter',
diff --git a/src/tools/snowflake-id-decoder/index.ts b/src/tools/snowflake-id-decoder/index.ts
new file mode 100644
index 00000000..6e5855e5
--- /dev/null
+++ b/src/tools/snowflake-id-decoder/index.ts
@@ -0,0 +1,12 @@
+import { Snowflake } from '@vicons/tabler';
+import { defineTool } from '../tool';
+
+export const tool = defineTool({
+  name: 'Snowflake id decoder',
+  path: '/snowflake-id-decoder',
+  description: 'Decode Twitter, Discord, Instagram or Mastodon snowflake ids into timestamps, worker ids and sequences',
+  keywords: ['snowflake', 'twitter', 'discord', 'instagram', 'mastodon', 'id', 'timestamp', 'decoder'],
+  component: () => import('./snowflake-id-decoder.vue'),
+  icon: Snowflake,
+  createdAt: new Date('2026-10-01'),
+});
diff --git a/src/tools/snowflake-id-decoder/snowflake-id-decoder.models.test.ts b/src/tools/snowflake-id-decoder/snowflake-id-decoder.models.test.ts
new file mode 100644
index 00000000..12317c29
--- /dev/null
+++ b/src/tools/snowflake-id-decoder/snowflake-id-decoder.models.test.ts
@@ -0,0 +1,40 @@
+import { describe, expect, it } from 'vitest';
+import { decodeSnowflake } from './snowflake-id-decoder.models';
+
+describe('snowflake-id-decoder', () => {
+  it('decodes a Twitter snowflake against the Twitter epoch', () => {
+    // 565419792856637440 was posted on 2015-02-09
+    const decoded = decodeSnowflake('565419792856637440', 1288834974657);
+    expect(decoded.timestamp).toBe(1423641558265);
+    expect(decoded.isoDate).toContain('2015-02-11');
+  });
+
+  it('decodes a Discord id against the Discord epoch', () => {
+    // Discord docs example: id 175928847299117063 -> 2016-04-30T11:18:25.796Z
+    const decoded = decodeSnowflake('175928847299117063', 1420070400000);
+    expect(decoded.timestamp).toBe(1462015105796);
+    expect(decoded.isoDate).toBe('2016-04-30 11:18:25 UTC');
+    expect(decoded.datacenterId).toBe(1);
+    expect(decoded.workerId).toBe(0);
+    expect(decoded.sequence).toBe(7);
+  });
+
+  it('rejects non-numeric input', () => {
+    expect(() => decodeSnowflake('abc', 0)).toThrow('positive integer');
+    expect(() => decodeSnowflake('12 34', 0)).toThrow('positive integer');
+    expect(() => decodeSnowflake('-5', 0)).toThrow('positive integer');
+  });
+
+  it('handles very large ids beyond Number safe range', () => {
+    // 2^63-1 must not lose precision
+    const decoded = decodeSnowflake('9223372036854775807', 0);
+    expect(decoded.timestamp).toBe(Number(9223372036854775807n >> 22n));
+  });
+
+  it('extracts sequence bits', () => {
+    // 0b1 << 22 | sequence 0b101010101010
+    const id = ((1n << 22n) | 0b101010101010n).toString();
+    const decoded = decodeSnowflake(id, 0);
+    expect(decoded.sequence).toBe(0b101010101010);
+  });
+});
diff --git a/src/tools/snowflake-id-decoder/snowflake-id-decoder.models.ts b/src/tools/snowflake-id-decoder/snowflake-id-decoder.models.ts
new file mode 100644
index 00000000..cb5f63a1
--- /dev/null
+++ b/src/tools/snowflake-id-decoder/snowflake-id-decoder.models.ts
@@ -0,0 +1,52 @@
+export interface SnowflakePlatform {
+  key: string
+  label: string
+  epoch: number
+}
+
+/** Well-known Snowflake epochs. Twitter uses a custom 41-bit timestamp; the
+ *  others use the standard 64-bit layout with a platform-specific epoch. */
+export const SNOWFLAKE_PLATFORMS: SnowflakePlatform[] = [
+  { key: 'twitter', label: 'Twitter / X', epoch: 1288834974657 },
+  { key: 'discord', label: 'Discord', epoch: 1420070400000 },
+  { key: 'instagram', label: 'Instagram', epoch: 1314220021721 },
+  { key: 'mastodon', label: 'Mastodon', epoch: 0 },
+  { key: 'custom', label: 'Custom epoch', epoch: 0 },
+];
+
+export interface SnowflakeDecoded {
+  /** Millisecond Unix timestamp encoded in the id. */
+  timestamp: number
+  isoDate: string
+  /** Datacenter / worker / sequence when the platform uses the standard layout. */
+  workerId: number
+  datacenterId: number
+  sequence: number
+}
+
+function parseSnowflakeId(id: string): bigint {
+  const trimmed = id.trim();
+  if (!/^\d{1,20}$/.test(trimmed)) {
+    throw new Error('A snowflake id is a positive integer');
+  }
+  return BigInt(trimmed);
+}
+
+/** Standard 64-bit Snowflake: 1 unused sign bit, 41-bit ms timestamp,
+ *  5-bit datacenter, 5-bit worker, 12-bit sequence. */
+export function decodeSnowflake(id: string, epoch: number): SnowflakeDecoded {
+  const value = parseSnowflakeId(id);
+  const timestamp = Number((value >> 22n) & 0x1FFFFFFFFFFFFn) + epoch;
+  const datacenterId = Number((value >> 17n) & 0x1Fn);
+  const workerId = Number((value >> 12n) & 0x1Fn);
+  const sequence = Number(value & 0xFFFn);
+
+  const date = new Date(timestamp);
+  return {
+    timestamp,
+    isoDate: `${date.toISOString().replace('T', ' ').replace(/\..+/, '')} UTC`,
+    workerId,
+    datacenterId,
+    sequence,
+  };
+}
diff --git a/src/tools/snowflake-id-decoder/snowflake-id-decoder.vue b/src/tools/snowflake-id-decoder/snowflake-id-decoder.vue
new file mode 100644
index 00000000..ef240629
--- /dev/null
+++ b/src/tools/snowflake-id-decoder/snowflake-id-decoder.vue
@@ -0,0 +1,105 @@
+<script setup lang="ts">
+import { SNOWFLAKE_PLATFORMS, type SnowflakePlatform, decodeSnowflake } from './snowflake-id-decoder.models';
+import { withDefaultOnError } from '@/utils/defaults';
+import { useValidation } from '@/composable/validation';
+
+const id = ref('175928847299117063');
+const platformKey = useStorage('snowflake:platform', 'discord');
+const customEpoch = ref<number | null>(null);
+
+const platform = computed<SnowflakePlatform>(() =>
+  SNOWFLAKE_PLATFORMS.find(p => p.key === platformKey.value) ?? SNOWFLAKE_PLATFORMS[1]!,
+);
+const effectiveEpoch = computed(() => (platformKey.value === 'custom' ? Number(customEpoch.value ?? 0) : platform.value.epoch));
+
+const validation = useValidation({
+  source: id,
+  rules: [
+    {
+      validator: value => !value || /^\d{1,20}$/.test(value.trim()),
+      message: 'A snowflake id is a positive integer (up to 20 digits)',
+    },
+  ],
+});
+
+const decoded = computed(() =>
+  withDefaultOnError(() => (id.value.trim() && validation.isValid ? decodeSnowflake(id.value, effectiveEpoch.value) : undefined), undefined),
+);
+
+const epochOptions = SNOWFLAKE_PLATFORMS.map(p => ({ label: p.label, value: p.key }));
+</script>
+
+<template>
+  <div style="max-width: 640px; margin: 0 auto;">
+    <c-card mb-3>
+      <c-input-text
+        v-model:value="id"
+        label="Snowflake id"
+        placeholder="e.g. 175928847299117063"
+        :validation="id ? validation : undefined"
+        mb-3
+      />
+
+      <n-grid cols="2" x-gap="12">
+        <n-gi>
+          <c-select v-model:value="platformKey" label="Platform" label-position="top" :options="epochOptions" />
+        </n-gi>
+        <n-gi>
+          <c-input-text
+            v-if="platformKey === 'custom'"
+            v-model:value="customEpoch"
+            label="Custom epoch (ms)"
+            placeholder="e.g. 0"
+          />
+        </n-gi>
+      </n-grid>
+    </c-card>
+
+    <c-card v-if="decoded">
+      <n-table>
+        <tbody>
+          <tr>
+            <td class="labels">
+              Timestamp (ms):
+            </td>
+            <td>{{ decoded.timestamp }}</td>
+          </tr>
+          <tr>
+            <td class="labels">
+              Date:
+            </td>
+            <td>{{ decoded.isoDate }}</td>
+          </tr>
+          <tr v-if="platformKey !== 'twitter'">
+            <td class="labels">
+              Datacenter id:
+            </td>
+            <td>{{ decoded.datacenterId }}</td>
+          </tr>
+          <tr v-if="platformKey !== 'twitter'">
+            <td class="labels">
+              Worker id:
+            </td>
+            <td>{{ decoded.workerId }}</td>
+          </tr>
+          <tr>
+            <td class="labels">
+              Sequence:
+            </td>
+            <td>{{ decoded.sequence }}</td>
+          </tr>
+        </tbody>
+      </n-table>
+      <div mt-2 text-xs op-60>
+        Epoch: {{ effectiveEpoch }} ms · layout: 41-bit timestamp / 5-bit datacenter / 5-bit worker / 12-bit sequence
+      </div>
+    </c-card>
+  </div>
+</template>
+
+<style scoped lang="less">
+.labels {
+  width: 180px;
+  font-weight: bold;
+}
+</style>