diff --git a/apps/stage-pocket/src/modules/posthog.ts b/apps/stage-pocket/src/modules/posthog.ts
index af8a46f8b..dd6b87d96 100644
--- a/apps/stage-pocket/src/modules/posthog.ts
+++ b/apps/stage-pocket/src/modules/posthog.ts
@@ -1,6 +1,8 @@
 import posthog from 'posthog-js'
 
-posthog.init('phc_pzjziJjrVZpa9SqnQqq0QEKvkmuCPH7GDTA6TbRTEf9', {
-  api_host: 'https://us.i.posthog.com',
-  person_profiles: 'identified_only', // or 'always' to create profiles for anonymous users as well
+import { DEFAULT_POSTHOG_CONFIG, POSTHOG_PROJECT_KEY_POCKET } from '../../../../posthog.config'
+
+posthog.init(POSTHOG_PROJECT_KEY_POCKET, {
+  ...DEFAULT_POSTHOG_CONFIG,
+  // Project-specific config...
 })
diff --git a/apps/stage-pocket/vite-env.d.ts b/apps/stage-pocket/vite-env.d.ts
index 0a7646264..529f0abf7 100644
--- a/apps/stage-pocket/vite-env.d.ts
+++ b/apps/stage-pocket/vite-env.d.ts
@@ -1,9 +1,8 @@
+/// <reference types="vite/client" />
+/// <reference types="../../vite-env.d.ts" />
+
 interface ImportMetaEnv {
   readonly VITE_APP_TARGET_HUGGINGFACE_SPACE: boolean
   readonly VITE_PLATFORM: 'ios' | 'android' | 'web'
   // more env variables...
 }
-
-interface ImportMeta {
-  readonly env: ImportMetaEnv
-}
diff --git a/apps/stage-tamagotchi/src/renderer/modules/posthog.ts b/apps/stage-tamagotchi/src/renderer/modules/posthog.ts
index c27aecddf..1ae0c0d33 100644
--- a/apps/stage-tamagotchi/src/renderer/modules/posthog.ts
+++ b/apps/stage-tamagotchi/src/renderer/modules/posthog.ts
@@ -1,6 +1,8 @@
 import posthog from 'posthog-js'
 
-posthog.init('phc_rljw376z5gt6vXJlc3sTr7hFbXodciY9THEQXIRnW53', {
-  api_host: 'https://us.i.posthog.com',
-  person_profiles: 'identified_only', // or 'always' to create profiles for anonymous users as well
+import { DEFAULT_POSTHOG_CONFIG, POSTHOG_PROJECT_KEY_DESKTOP } from '../../../../../posthog.config'
+
+posthog.init(POSTHOG_PROJECT_KEY_DESKTOP, {
+  ...DEFAULT_POSTHOG_CONFIG,
+  // Project-specific config...
 })
diff --git a/apps/stage-tamagotchi/vite-env.d.ts b/apps/stage-tamagotchi/vite-env.d.ts
new file mode 100644
index 000000000..6f1818c56
--- /dev/null
+++ b/apps/stage-tamagotchi/vite-env.d.ts
@@ -0,0 +1,6 @@
+/// <reference types="vite/client" />
+/// <reference types="../../vite-env.d.ts" />
+
+interface ImportMetaEnv {
+  // Env variables...
+}
diff --git a/apps/stage-web/src/modules/posthog.ts b/apps/stage-web/src/modules/posthog.ts
index af8a46f8b..f9d8a81b0 100644
--- a/apps/stage-web/src/modules/posthog.ts
+++ b/apps/stage-web/src/modules/posthog.ts
@@ -1,6 +1,8 @@
 import posthog from 'posthog-js'
 
-posthog.init('phc_pzjziJjrVZpa9SqnQqq0QEKvkmuCPH7GDTA6TbRTEf9', {
-  api_host: 'https://us.i.posthog.com',
-  person_profiles: 'identified_only', // or 'always' to create profiles for anonymous users as well
+import { DEFAULT_POSTHOG_CONFIG, POSTHOG_PROJECT_KEY_WEB } from '../../../../posthog.config'
+
+posthog.init(POSTHOG_PROJECT_KEY_WEB, {
+  ...DEFAULT_POSTHOG_CONFIG,
+  // Project-specific config...
 })
diff --git a/apps/stage-web/vite-env.d.ts b/apps/stage-web/vite-env.d.ts
index 03b4499bc..7938100e4 100644
--- a/apps/stage-web/vite-env.d.ts
+++ b/apps/stage-web/vite-env.d.ts
@@ -1,8 +1,7 @@
+/// <reference types="vite/client" />
+/// <reference types="../../vite-env.d.ts" />
+
 interface ImportMetaEnv {
   readonly VITE_APP_TARGET_HUGGINGFACE_SPACE: boolean
   // more env variables...
 }
-
-interface ImportMeta {
-  readonly env: ImportMetaEnv
-}
diff --git a/docs/.vitepress/modules/posthog.ts b/docs/.vitepress/modules/posthog.ts
index af8a46f8b..8c12f2a87 100644
--- a/docs/.vitepress/modules/posthog.ts
+++ b/docs/.vitepress/modules/posthog.ts
@@ -1,6 +1,8 @@
 import posthog from 'posthog-js'
 
-posthog.init('phc_pzjziJjrVZpa9SqnQqq0QEKvkmuCPH7GDTA6TbRTEf9', {
-  api_host: 'https://us.i.posthog.com',
-  person_profiles: 'identified_only', // or 'always' to create profiles for anonymous users as well
+import { DEFAULT_POSTHOG_CONFIG, POSTHOG_PROJECT_KEY_DOCS } from '../../../posthog.config'
+
+posthog.init(POSTHOG_PROJECT_KEY_DOCS, {
+  ...DEFAULT_POSTHOG_CONFIG,
+  // Project-specific config...
 })
diff --git a/docs/vite-env.d.ts b/docs/vite-env.d.ts
new file mode 100644
index 000000000..86b99fbb1
--- /dev/null
+++ b/docs/vite-env.d.ts
@@ -0,0 +1,6 @@
+/// <reference types="vite/client" />
+/// <reference types="../vite-env.d.ts" />
+
+interface ImportMetaEnv {
+  // Env variables...
+}
diff --git a/package.json b/package.json
index faee92733..386d627f1 100644
--- a/package.json
+++ b/package.json
@@ -58,6 +58,7 @@
     "eslint-plugin-oxlint": "^1.35.0",
     "nano-staged": "catalog:",
     "oxlint": "^1.35.0",
+    "posthog-js": "catalog:",
     "publint": "^0.3.16",
     "rollup": "^4.54.0",
     "simple-git-hooks": "^2.13.1",
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index cba774520..7ae2325b7 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -209,6 +209,9 @@ importers:
       oxlint:
         specifier: ^1.35.0
         version: 1.36.0
+      posthog-js:
+        specifier: 'catalog:'
+        version: 1.306.1
       publint:
         specifier: ^0.3.16
         version: 0.3.16
diff --git a/posthog.config.ts b/posthog.config.ts
new file mode 100644
index 000000000..82f9f792c
--- /dev/null
+++ b/posthog.config.ts
@@ -0,0 +1,29 @@
+/// <reference types="vite/client" />
+
+import type { PostHogConfig } from 'posthog-js'
+
+// These PostHog project API keys are considered public and are safe
+// to be stored here as clear text.
+
+export const POSTHOG_PROJECT_KEY_WEB
+  = import.meta.env.VITE_POSTHOG_PROJECT_KEY_WEB
+    ?? 'phc_pzjziJjrVZpa9SqnQqq0QEKvkmuCPH7GDTA6TbRTEf9' // cspell:disable-line
+
+export const POSTHOG_PROJECT_KEY_DESKTOP
+  = import.meta.env.VITE_POSTHOG_PROJECT_KEY_DESKTOP
+    ?? 'phc_rljw376z5gt6vXJlc3sTr7hFbXodciY9THEQXIRnW53'// cspell:disable-line
+
+// FIXME: Using the same key for 'web' for now.
+export const POSTHOG_PROJECT_KEY_POCKET
+  = import.meta.env.VITE_POSTHOG_PROJECT_KEY_POCKET
+    ?? 'phc_pzjziJjrVZpa9SqnQqq0QEKvkmuCPH7GDTA6TbRTEf9' // cspell:disable-line
+
+// FIXME: Using the same key for 'web' for now.
+export const POSTHOG_PROJECT_KEY_DOCS
+  = import.meta.env.VITE_POSTHOG_PROJECT_KEY_DOCS
+    ?? 'phc_pzjziJjrVZpa9SqnQqq0QEKvkmuCPH7GDTA6TbRTEf9' // cspell:disable-line
+
+export const DEFAULT_POSTHOG_CONFIG = {
+  api_host: 'https://us.i.posthog.com',
+  person_profiles: 'identified_only', // or 'always' to create profiles for anonymous users as well
+} as const satisfies Partial<PostHogConfig>
diff --git a/vite-env.d.ts b/vite-env.d.ts
new file mode 100644
index 000000000..5ffa92c98
--- /dev/null
+++ b/vite-env.d.ts
@@ -0,0 +1,12 @@
+/// <reference types="vite/client" />
+
+interface ImportMetaEnv {
+  readonly VITE_POSTHOG_PROJECT_KEY_WEB?: string
+  readonly VITE_POSTHOG_PROJECT_KEY_DESKTOP?: string
+  readonly VITE_POSTHOG_PROJECT_KEY_POCKET?: string
+  readonly VITE_POSTHOG_PROJECT_KEY_DOCS?: string
+}
+
+interface ImportMeta {
+  readonly env: ImportMetaEnv
+}