diff --git a/services/web/app/src/infrastructure/ExpressLocals.js b/services/web/app/src/infrastructure/ExpressLocals.js
index ede2532e25..e3aac6f390 100644
--- a/services/web/app/src/infrastructure/ExpressLocals.js
+++ b/services/web/app/src/infrastructure/ExpressLocals.js
@@ -122,7 +122,8 @@ module.exports = function (webRouter, privateApiRouter, publicApiRouter) {
 
     const cdnAvailable =
       Settings.cdn && Settings.cdn.web && !!Settings.cdn.web.host
-    const cdnBlocked = req.query.nocdn === 'true' || req.session.cdnBlocked
+    const cdnBlocked =
+      req.query.nocdn === 'true' || req.session.cdnBlocked || false
     const userId = SessionManager.getLoggedInUserId(req.session)
     if (cdnBlocked && req.session.cdnBlocked == null) {
       logger.debug(
@@ -135,6 +136,10 @@ module.exports = function (webRouter, privateApiRouter, publicApiRouter) {
       })
       req.session.cdnBlocked = true
     }
+    Metrics.inc('cdn_blocked', 1, {
+      path: userId ? 'logged-in' : 'pre-login',
+      method: String(cdnBlocked),
+    })
     const host = req.headers && req.headers.host
     const isSmoke = host.slice(0, 5).toLowerCase() === 'smoke'
     if (cdnAvailable && !isSmoke && !cdnBlocked) {
diff --git a/services/web/test/acceptance/config/settings.test.defaults.js b/services/web/test/acceptance/config/settings.test.defaults.js
index bf8e095ba4..f292b33cf0 100644
--- a/services/web/test/acceptance/config/settings.test.defaults.js
+++ b/services/web/test/acceptance/config/settings.test.defaults.js
@@ -23,6 +23,11 @@ module.exports = {
     : ['example.com'],
 
   statusPageUrl: 'status.example.com',
+  cdn: {
+    web: {
+      host: 'cdn.example.com',
+    },
+  },
 
   apis: {
     linkedUrlProxy: {
diff --git a/services/web/test/acceptance/src/CDNMigrationTests.js b/services/web/test/acceptance/src/CDNMigrationTests.js
new file mode 100644
index 0000000000..3d44412ce6
--- /dev/null
+++ b/services/web/test/acceptance/src/CDNMigrationTests.js
@@ -0,0 +1,95 @@
+const { expect } = require('chai')
+const User = require('./helpers/User').promises
+const {
+  promises: { getMetric },
+} = require('./helpers/metrics')
+
+describe('CDNMigration', function () {
+  let anon, user
+  beforeEach(async function () {
+    anon = new User()
+    user = new User()
+    await user.login()
+  })
+  let noCdnPreLogin, noCdnLoggedIn
+  let cdnBlockedTruePreLogin, cdnBlockedTrueLoggedIn
+  let cdnBlockedFalsePreLogin, cdnBlockedFalseLoggedIn
+
+  async function getNoCdn(path) {
+    return await getMetric(
+      line => line.includes('no_cdn') && line.includes(path)
+    )
+  }
+  async function getCdnBlocked(path, method) {
+    return await getMetric(
+      line =>
+        line.includes('cdn_blocked') &&
+        line.includes(`path="${path}"`) &&
+        line.includes(`method="${method}"`)
+    )
+  }
+
+  beforeEach(async function () {
+    noCdnPreLogin = await getNoCdn('pre-login')
+    noCdnLoggedIn = await getNoCdn('logged-in')
+    cdnBlockedTruePreLogin = await getCdnBlocked('pre-login', 'true')
+    cdnBlockedTrueLoggedIn = await getCdnBlocked('logged-in', 'true')
+    cdnBlockedFalsePreLogin = await getCdnBlocked('pre-login', 'false')
+    cdnBlockedFalseLoggedIn = await getCdnBlocked('logged-in', 'false')
+  })
+
+  describe('pre-login', function () {
+    it('should collect no_cdn', async function () {
+      await anon.doRequest('GET', '/login?nocdn=true')
+      expect(await getNoCdn('pre-login')).to.equal(noCdnPreLogin + 1)
+    })
+    it('should collect cdn_blocked', async function () {
+      await anon.doRequest('GET', '/login')
+      await anon.doRequest('GET', '/login')
+      await anon.doRequest('GET', '/login')
+      expect(await getCdnBlocked('pre-login', 'false')).to.equal(
+        cdnBlockedFalsePreLogin + 3
+      )
+      expect(await getCdnBlocked('pre-login', 'true')).to.equal(
+        cdnBlockedTruePreLogin
+      )
+    })
+    it('should collect cdn_blocked after nocdn', async function () {
+      await anon.doRequest('GET', '/login?nocdn=true')
+      await anon.doRequest('GET', '/login')
+      expect(await getCdnBlocked('pre-login', 'false')).to.equal(
+        cdnBlockedFalsePreLogin
+      )
+      expect(await getCdnBlocked('pre-login', 'true')).to.equal(
+        cdnBlockedTruePreLogin + 2
+      )
+    })
+  })
+  describe('logged-in', function () {
+    it('should collect no_cdn', async function () {
+      await user.doRequest('GET', '/project?nocdn=true')
+      expect(await getNoCdn('logged-in')).to.equal(noCdnLoggedIn + 1)
+    })
+    it('should collect cdn_blocked=false before nocdn', async function () {
+      await user.doRequest('GET', '/project')
+      await user.doRequest('GET', '/project')
+      await user.doRequest('GET', '/project')
+      expect(await getCdnBlocked('logged-in', 'false')).to.equal(
+        cdnBlockedFalseLoggedIn + 3
+      )
+      expect(await getCdnBlocked('logged-in', 'true')).to.equal(
+        cdnBlockedTrueLoggedIn
+      )
+    })
+    it('should collect cdn_blocked=true after nocdn=true', async function () {
+      await user.doRequest('GET', '/project?nocdn=true')
+      await user.doRequest('GET', '/project')
+      expect(await getCdnBlocked('logged-in', 'false')).to.equal(
+        cdnBlockedFalseLoggedIn
+      )
+      expect(await getCdnBlocked('logged-in', 'true')).to.equal(
+        cdnBlockedTrueLoggedIn + 2
+      )
+    })
+  })
+})