diff --git a/services/web/app/src/Features/Collaborators/CollaboratorsController.js b/services/web/app/src/Features/Collaborators/CollaboratorsController.js
index c3af1ba18b..a86f4fface 100644
--- a/services/web/app/src/Features/Collaborators/CollaboratorsController.js
+++ b/services/web/app/src/Features/Collaborators/CollaboratorsController.js
@@ -167,5 +167,17 @@ async function getShareTokens(req, res) {
     )
   }
 
+  if (tokens.readOnly) {
+    tokens.readOnlyHashPrefix = TokenAccessHandler.createTokenHashPrefix(
+      tokens.readOnly
+    )
+  }
+
+  if (tokens.readAndWrite) {
+    tokens.readAndWriteHashPrefix = TokenAccessHandler.createTokenHashPrefix(
+      tokens.readAndWrite
+    )
+  }
+
   res.json(tokens)
 }
diff --git a/services/web/app/src/Features/TokenAccess/TokenAccessController.js b/services/web/app/src/Features/TokenAccess/TokenAccessController.js
index 87a4723448..4e0fe30b89 100644
--- a/services/web/app/src/Features/TokenAccess/TokenAccessController.js
+++ b/services/web/app/src/Features/TokenAccess/TokenAccessController.js
@@ -96,6 +96,7 @@ async function tokenAccessPage(req, res, next) {
         return res.redirect(302, docPublishedInfo.published_path)
       }
     }
+
     res.render('project/token/access', {
       postUrl: makePostUrl(token),
     })
@@ -225,12 +226,15 @@ async function checkAndGetProjectOrResponseAction(
 
 async function grantTokenAccessReadAndWrite(req, res, next) {
   const { token } = req.params
-  const { confirmedByUser } = req.body
+  const { confirmedByUser, tokenHashPrefix } = req.body
   const userId = SessionManager.getLoggedInUserId(req.session)
   if (!TokenAccessHandler.isReadAndWriteToken(token)) {
     return res.sendStatus(400)
   }
   const tokenType = TokenAccessHandler.TOKEN_TYPES.READ_AND_WRITE
+
+  TokenAccessHandler.checkTokenHashPrefix(token, tokenHashPrefix, tokenType)
+
   try {
     const [project, action] = await checkAndGetProjectOrResponseAction(
       tokenType,
@@ -268,6 +272,7 @@ async function grantTokenAccessReadAndWrite(req, res, next) {
       userId,
       project._id
     )
+
     return res.json({
       redirect: `/project/${project._id}`,
       tokenAccessGranted: tokenType,
@@ -285,12 +290,16 @@ async function grantTokenAccessReadAndWrite(req, res, next) {
 
 async function grantTokenAccessReadOnly(req, res, next) {
   const { token } = req.params
-  const { confirmedByUser } = req.body
+  const { confirmedByUser, tokenHashPrefix } = req.body
   const userId = SessionManager.getLoggedInUserId(req.session)
   if (!TokenAccessHandler.isReadOnlyToken(token)) {
     return res.sendStatus(400)
   }
+
   const tokenType = TokenAccessHandler.TOKEN_TYPES.READ_ONLY
+
+  TokenAccessHandler.checkTokenHashPrefix(token, tokenHashPrefix, tokenType)
+
   const docPublishedInfo =
     await TokenAccessHandler.promises.getV1DocPublishedInfo(token)
   if (docPublishedInfo.allow === false) {
@@ -333,6 +342,7 @@ async function grantTokenAccessReadOnly(req, res, next) {
       userId,
       project._id
     )
+
     return res.json({
       redirect: `/project/${project._id}`,
       tokenAccessGranted: tokenType,
diff --git a/services/web/app/src/Features/TokenAccess/TokenAccessHandler.js b/services/web/app/src/Features/TokenAccess/TokenAccessHandler.js
index 6af5ca2045..ee8235158b 100644
--- a/services/web/app/src/Features/TokenAccess/TokenAccessHandler.js
+++ b/services/web/app/src/Features/TokenAccess/TokenAccessHandler.js
@@ -2,6 +2,7 @@ const { Project } = require('../../models/Project')
 const PublicAccessLevels = require('../Authorization/PublicAccessLevels')
 const PrivilegeLevels = require('../Authorization/PrivilegeLevels')
 const { ObjectId } = require('mongodb')
+const Metrics = require('@overleaf/metrics')
 const Settings = require('@overleaf/settings')
 const logger = require('@overleaf/logger')
 const V1Api = require('../V1/V1Api')
@@ -279,6 +280,32 @@ const TokenAccessHandler = {
       callback(null, body)
     })
   },
+
+  createTokenHashPrefix(token) {
+    const hash = crypto.createHash('sha256')
+    hash.update(token)
+    return hash.digest('hex').slice(0, 6)
+  },
+
+  checkTokenHashPrefix(token, tokenHashPrefix, type) {
+    let hashPrefixStatus
+
+    if (!tokenHashPrefix) {
+      hashPrefixStatus = 'missing'
+    } else {
+      const hashPrefix = TokenAccessHandler.createTokenHashPrefix(token)
+      if (hashPrefix === tokenHashPrefix.replace('#', '')) {
+        hashPrefixStatus = 'match'
+      } else {
+        hashPrefixStatus = 'mismatch'
+      }
+    }
+
+    Metrics.inc('link-sharing.hash-check', {
+      path: type,
+      status: hashPrefixStatus,
+    })
+  },
 }
 
 TokenAccessHandler.promises = promisifyAll(TokenAccessHandler, {
diff --git a/services/web/frontend/js/features/share-project-modal/components/link-sharing.jsx b/services/web/frontend/js/features/share-project-modal/components/link-sharing.jsx
index 13c0ec5074..a37a631b27 100644
--- a/services/web/frontend/js/features/share-project-modal/components/link-sharing.jsx
+++ b/services/web/frontend/js/features/share-project-modal/components/link-sharing.jsx
@@ -15,7 +15,7 @@ import { getJSON } from '../../../infrastructure/fetch-json'
 import useAbortController from '../../../shared/hooks/use-abort-controller'
 import { debugConsole } from '@/utils/debugging'
 
-export default function LinkSharing({ canAddCollaborators }) {
+export default function LinkSharing() {
   const [inflight, setInflight] = useState(false)
 
   const { monitorRequest } = useShareProjectContext()
@@ -61,7 +61,6 @@ export default function LinkSharing({ canAddCollaborators }) {
         <TokenBasedSharing
           setAccessLevel={setAccessLevel}
           inflight={inflight}
-          canAddCollaborators={canAddCollaborators}
         />
       )
 
@@ -81,10 +80,6 @@ export default function LinkSharing({ canAddCollaborators }) {
   }
 }
 
-LinkSharing.propTypes = {
-  canAddCollaborators: PropTypes.bool,
-}
-
 function PrivateSharing({ setAccessLevel, inflight, projectId }) {
   const { t } = useTranslation()
   return (
@@ -117,7 +112,7 @@ PrivateSharing.propTypes = {
   projectId: PropTypes.string,
 }
 
-function TokenBasedSharing({ setAccessLevel, inflight, canAddCollaborators }) {
+function TokenBasedSharing({ setAccessLevel, inflight }) {
   const { t } = useTranslation()
   const { _id: projectId } = useProjectContext()
 
@@ -152,6 +147,7 @@ function TokenBasedSharing({ setAccessLevel, inflight, canAddCollaborators }) {
           <strong>{t('anyone_with_link_can_edit')}</strong>
           <AccessToken
             token={tokens?.readAndWrite}
+            tokenHashPrefix={tokens?.readAndWriteHashPrefix}
             path="/"
             tooltipId="tooltip-copy-link-rw"
           />
@@ -160,6 +156,7 @@ function TokenBasedSharing({ setAccessLevel, inflight, canAddCollaborators }) {
           <strong>{t('anyone_with_link_can_view')}</strong>
           <AccessToken
             token={tokens?.readOnly}
+            tokenHashPrefix={tokens?.readOnlyHashPrefix}
             path="/read/"
             tooltipId="tooltip-copy-link-ro"
           />
@@ -172,7 +169,6 @@ function TokenBasedSharing({ setAccessLevel, inflight, canAddCollaborators }) {
 TokenBasedSharing.propTypes = {
   setAccessLevel: PropTypes.func.isRequired,
   inflight: PropTypes.bool,
-  canAddCollaborators: PropTypes.bool,
 }
 
 function LegacySharing({ accessLevel, setAccessLevel, inflight }) {
@@ -229,6 +225,7 @@ export function ReadOnlyTokenLink() {
           <strong>{t('anyone_with_link_can_view')}</strong>
           <AccessToken
             token={tokens?.readOnly}
+            tokenHashPrefix={tokens?.readOnlyHashPrefix}
             path="/read/"
             tooltipId="tooltip-copy-link-ro"
           />
@@ -238,7 +235,7 @@ export function ReadOnlyTokenLink() {
   )
 }
 
-function AccessToken({ token, path, tooltipId }) {
+function AccessToken({ token, tokenHashPrefix, path, tooltipId }) {
   const { t } = useTranslation()
   const { isAdmin } = useUserContext()
 
@@ -254,7 +251,9 @@ function AccessToken({ token, path, tooltipId }) {
   if (isAdmin) {
     origin = window.ExposedSettings.siteUrl
   }
-  const link = `${origin}${path}${token}`
+  const link = `${origin}${path}${token}${
+    tokenHashPrefix ? `#${tokenHashPrefix}` : ''
+  }`
 
   return (
     <div className="access-token">
@@ -266,6 +265,7 @@ function AccessToken({ token, path, tooltipId }) {
 
 AccessToken.propTypes = {
   token: PropTypes.string,
+  tokenHashPrefix: PropTypes.string,
   tooltipId: PropTypes.string.isRequired,
   path: PropTypes.string.isRequired,
 }
diff --git a/services/web/frontend/js/features/share-project-modal/components/share-modal-body.jsx b/services/web/frontend/js/features/share-project-modal/components/share-modal-body.jsx
index 85a36650d3..02938c37f4 100644
--- a/services/web/frontend/js/features/share-project-modal/components/share-modal-body.jsx
+++ b/services/web/frontend/js/features/share-project-modal/components/share-modal-body.jsx
@@ -69,7 +69,7 @@ export default function ShareModalBody() {
           {isProjectOwner && (
             <>
               <br />
-              <LinkSharing canAddCollaborators={canAddCollaborators} />
+              <LinkSharing />
             </>
           )}
 
@@ -108,7 +108,7 @@ export default function ShareModalBody() {
           {isProjectOwner && (
             <>
               <br />
-              <LinkSharing canAddCollaborators={canAddCollaborators} />
+              <LinkSharing />
             </>
           )}
 
@@ -122,9 +122,7 @@ export default function ShareModalBody() {
     default:
       return (
         <>
-          {isProjectOwner && (
-            <LinkSharing canAddCollaborators={canAddCollaborators} />
-          )}
+          {isProjectOwner && <LinkSharing />}
 
           <OwnerInfo />
 
diff --git a/services/web/frontend/js/main/token-access.js b/services/web/frontend/js/main/token-access.js
index 64ffb7b7ff..68cb1075ab 100644
--- a/services/web/frontend/js/main/token-access.js
+++ b/services/web/frontend/js/main/token-access.js
@@ -43,13 +43,13 @@ App.controller('TokenAccessPageController', [
       const parsedData = JSON.parse(textData)
       const { postUrl, csrfToken } = parsedData
       $scope.accessInFlight = true
-
       $http({
         method: 'POST',
         url: postUrl,
         data: {
           _csrf: csrfToken,
           confirmedByUser,
+          tokenHashPrefix: window.location.hash,
         },
       }).then(
         function successCallback(response) {
diff --git a/services/web/test/acceptance/src/TokenAccessTests.js b/services/web/test/acceptance/src/TokenAccessTests.js
index 35ac5ec155..d8e548113a 100644
--- a/services/web/test/acceptance/src/TokenAccessTests.js
+++ b/services/web/test/acceptance/src/TokenAccessTests.js
@@ -345,11 +345,14 @@ describe('TokenAccess', function () {
         (error, response, body) => {
           expect(error).to.equal(null)
           expect(response.statusCode).to.equal(200)
-          expect(body).to.deep.equal({
+          expect(body).to.include({
             readOnly: this.tokens.readOnly,
             readAndWrite: this.tokens.readAndWrite,
             readAndWritePrefix: this.tokens.readAndWritePrefix,
           })
+          expect(body.readOnlyHashPrefix).to.exist
+          expect(body.readAndWriteHashPrefix).to.exist
+          expect(Object.keys(body).length).to.equal(5)
           done()
         }
       )
@@ -494,7 +497,8 @@ describe('TokenAccess', function () {
               (error, response, body) => {
                 expect(error).to.equal(null)
                 expect(response.statusCode).to.equal(200)
-                expect(body).to.deep.equal({ readOnly: this.tokens.readOnly })
+                expect(body).to.include({ readOnly: this.tokens.readOnly })
+                expect(body.readOnlyHashPrefix).to.exist
                 cb()
               }
             )
@@ -709,7 +713,9 @@ describe('TokenAccess', function () {
               (error, response, body) => {
                 expect(error).to.equal(null)
                 expect(response.statusCode).to.equal(200)
-                expect(body).to.deep.equal({ readOnly: this.tokens.readOnly })
+                expect(body).to.include({ readOnly: this.tokens.readOnly })
+                expect(body.readOnlyHashPrefix).to.exist
+                expect(Object.keys(body).length).to.equal(2)
                 cb()
               }
             )
diff --git a/services/web/test/frontend/features/share-project-modal/components/share-project-modal.test.jsx b/services/web/test/frontend/features/share-project-modal/components/share-project-modal.test.jsx
index b5cb253f70..5996e6ac47 100644
--- a/services/web/test/frontend/features/share-project-modal/components/share-project-modal.test.jsx
+++ b/services/web/test/frontend/features/share-project-modal/components/share-project-modal.test.jsx
@@ -146,6 +146,14 @@ describe('<ShareProjectModal/>', function () {
   })
 
   it('handles access level "tokenBased"', async function () {
+    const tokens = {
+      readAndWrite: '6862414195fwtbrtrdtskb',
+      readAndWritePrefix: '6862414195',
+      readOnly: 'wrnjfzkysqkr',
+      readAndWriteHashPrefix: 'taEVki',
+      readOnlyHashPrefix: 'j2xYbL',
+    }
+    fetchMock.get(`/project/${project._id}/tokens`, tokens)
     renderWithEditorContext(<ShareProjectModal {...modalProps} />, {
       scope: { project: { ...project, publicAccesLevel: 'tokenBased' } },
     })
@@ -157,6 +165,13 @@ describe('<ShareProjectModal/>', function () {
       .not.to.be.null
     expect(screen.queryByText('Anyone with this link can edit this project'))
       .not.to.be.null
+
+    screen.getByText(
+      `https://www.test-overleaf.com/${tokens.readAndWrite}#${tokens.readAndWriteHashPrefix}`
+    )
+    screen.getByText(
+      `https://www.test-overleaf.com/read/${tokens.readOnly}#${tokens.readOnlyHashPrefix}`
+    )
   })
 
   it('handles legacy access level "readAndWrite"', async function () {
diff --git a/services/web/test/unit/src/Collaborators/CollaboratorsControllerTests.js b/services/web/test/unit/src/Collaborators/CollaboratorsControllerTests.js
index 9eb99105b3..0f50b76c84 100644
--- a/services/web/test/unit/src/Collaborators/CollaboratorsControllerTests.js
+++ b/services/web/test/unit/src/Collaborators/CollaboratorsControllerTests.js
@@ -23,6 +23,7 @@ describe('CollaboratorsController', function () {
         removeUserFromProject: sinon.stub().resolves(),
         setCollaboratorPrivilegeLevel: sinon.stub().resolves(),
       },
+      createTokenHashPrefix: sinon.stub().returns('abc123'),
     }
     this.CollaboratorsGetter = {
       promises: {
diff --git a/services/web/test/unit/src/TokenAccess/TokenAccessControllerTests.js b/services/web/test/unit/src/TokenAccess/TokenAccessControllerTests.js
index 015550e956..0beb92d794 100644
--- a/services/web/test/unit/src/TokenAccess/TokenAccessControllerTests.js
+++ b/services/web/test/unit/src/TokenAccess/TokenAccessControllerTests.js
@@ -29,6 +29,7 @@ describe('TokenAccessController', function () {
       isReadAndWriteToken: sinon.stub().returns(true),
       isReadOnlyToken: sinon.stub().returns(true),
       tokenAccessEnabledForProject: sinon.stub().returns(true),
+      checkTokenHashPrefix: sinon.stub(),
       promises: {
         addReadAndWriteUserToProject: sinon.stub().resolves(),
         addReadOnlyUserToProject: sinon.stub().resolves(),
@@ -78,7 +79,7 @@ describe('TokenAccessController', function () {
     describe('normal case', function () {
       beforeEach(function (done) {
         this.req.params = { token: this.token }
-        this.req.body = { confirmedByUser: true }
+        this.req.body = { confirmedByUser: true, tokenHashPrefix: 'prefix' }
         this.res.callback = done
         this.TokenAccessController.grantTokenAccessReadAndWrite(
           this.req,
@@ -104,6 +105,12 @@ describe('TokenAccessController', function () {
           { privileges: 'readAndWrite' }
         )
       })
+
+      it('checks token hash', function () {
+        expect(
+          this.TokenAccessHandler.checkTokenHashPrefix
+        ).to.have.been.calledWith(this.token, 'prefix', 'readAndWrite')
+      })
     })
 
     describe('when the access was already granted', function () {
@@ -124,13 +131,38 @@ describe('TokenAccessController', function () {
           .called
       })
     })
+
+    describe('hash prefix missing in request', function () {
+      beforeEach(function (done) {
+        this.req.params = { token: this.token }
+        this.req.body = { confirmedByUser: true }
+        this.res.callback = done
+        this.TokenAccessController.grantTokenAccessReadAndWrite(
+          this.req,
+          this.res,
+          done
+        )
+      })
+
+      it('grants read and write access', function () {
+        expect(
+          this.TokenAccessHandler.promises.addReadAndWriteUserToProject
+        ).to.have.been.calledWith(this.user._id, this.project._id)
+      })
+
+      it('sends missing hash to metrics', function () {
+        expect(
+          this.TokenAccessHandler.checkTokenHashPrefix
+        ).to.have.been.calledWith(this.token, undefined, 'readAndWrite')
+      })
+    })
   })
 
   describe('grantTokenAccessReadOnly', function () {
     describe('normal case', function () {
       beforeEach(function (done) {
         this.req.params = { token: this.token }
-        this.req.body = { confirmedByUser: true }
+        this.req.body = { confirmedByUser: true, tokenHashPrefix: 'prefix' }
         this.res.callback = done
         this.TokenAccessController.grantTokenAccessReadOnly(
           this.req,
@@ -156,6 +188,12 @@ describe('TokenAccessController', function () {
           { privileges: 'readOnly' }
         )
       })
+
+      it('sends checks if hash prefix matches', function () {
+        expect(
+          this.TokenAccessHandler.checkTokenHashPrefix
+        ).to.have.been.calledWith(this.token, 'prefix', 'readOnly')
+      })
     })
 
     describe('when the access was already granted', function () {
diff --git a/services/web/test/unit/src/TokenAccess/TokenAccessHandlerTests.js b/services/web/test/unit/src/TokenAccess/TokenAccessHandlerTests.js
index d85e2d867f..feeb79b16a 100644
--- a/services/web/test/unit/src/TokenAccess/TokenAccessHandlerTests.js
+++ b/services/web/test/unit/src/TokenAccess/TokenAccessHandlerTests.js
@@ -1,16 +1,3 @@
-/* eslint-disable
-    n/handle-callback-err,
-    max-len,
-    no-return-assign,
-    no-unused-vars,
-*/
-// TODO: This file was created by bulk-decaffeinate.
-// Fix any style issues and re-enable lint.
-/*
- * decaffeinate suggestions:
- * DS102: Remove unnecessary code created because of implicit returns
- * Full docs: https://github.com/decaffeinate/decaffeinate/blob/master/docs/suggestions.md
- */
 const SandboxedModule = require('sandboxed-module')
 const path = require('path')
 const sinon = require('sinon')
@@ -32,10 +19,11 @@ describe('TokenAccessHandler', function () {
     }
     this.userId = ObjectId()
     this.req = {}
-    return (this.TokenAccessHandler = SandboxedModule.require(modulePath, {
+    this.TokenAccessHandler = SandboxedModule.require(modulePath, {
       requires: {
         mongodb: { ObjectId },
         '../../models/Project': { Project: (this.Project = {}) },
+        '@overleaf/metrics': (this.Metrics = { inc: sinon.stub() }),
         '@overleaf/settings': (this.settings = {}),
         '../V1/V1Api': (this.V1Api = {
           request: sinon.stub(),
@@ -45,7 +33,7 @@ describe('TokenAccessHandler', function () {
           recordEventForUser: sinon.stub(),
         }),
       },
-    }))
+    })
   })
 
   describe('getTokenType', function () {
@@ -119,14 +107,15 @@ describe('TokenAccessHandler', function () {
 
   describe('addReadOnlyUserToProject', function () {
     beforeEach(function () {
-      return (this.Project.updateOne = sinon.stub().callsArgWith(2, null))
+      this.Project.updateOne = sinon.stub().callsArgWith(2, null)
     })
 
     it('should call Project.updateOne', function (done) {
-      return this.TokenAccessHandler.addReadOnlyUserToProject(
+      this.TokenAccessHandler.addReadOnlyUserToProject(
         this.userId,
         this.projectId,
         err => {
+          expect(err).to.not.exist
           expect(this.Project.updateOne.callCount).to.equal(1)
           expect(
             this.Project.updateOne.calledWith({
@@ -142,36 +131,36 @@ describe('TokenAccessHandler', function () {
             'project-joined',
             { mode: 'read-only' }
           )
-          return done()
+          done()
         }
       )
     })
 
     it('should not produce an error', function (done) {
-      return this.TokenAccessHandler.addReadOnlyUserToProject(
+      this.TokenAccessHandler.addReadOnlyUserToProject(
         this.userId,
         this.projectId,
         err => {
           expect(err).to.not.exist
-          return done()
+          done()
         }
       )
     })
 
     describe('when Project.updateOne produces an error', function () {
       beforeEach(function () {
-        return (this.Project.updateOne = sinon
+        this.Project.updateOne = sinon
           .stub()
-          .callsArgWith(2, new Error('woops')))
+          .callsArgWith(2, new Error('woops'))
       })
 
       it('should produce an error', function (done) {
-        return this.TokenAccessHandler.addReadOnlyUserToProject(
+        this.TokenAccessHandler.addReadOnlyUserToProject(
           this.userId,
           this.projectId,
           err => {
             expect(err).to.exist
-            return done()
+            done()
           }
         )
       })
@@ -180,14 +169,15 @@ describe('TokenAccessHandler', function () {
 
   describe('addReadAndWriteUserToProject', function () {
     beforeEach(function () {
-      return (this.Project.updateOne = sinon.stub().callsArgWith(2, null))
+      this.Project.updateOne = sinon.stub().callsArgWith(2, null)
     })
 
     it('should call Project.updateOne', function (done) {
-      return this.TokenAccessHandler.addReadAndWriteUserToProject(
+      this.TokenAccessHandler.addReadAndWriteUserToProject(
         this.userId,
         this.projectId,
         err => {
+          expect(err).to.not.exist
           expect(this.Project.updateOne.callCount).to.equal(1)
           expect(
             this.Project.updateOne.calledWith({
@@ -203,36 +193,36 @@ describe('TokenAccessHandler', function () {
             'project-joined',
             { mode: 'read-write' }
           )
-          return done()
+          done()
         }
       )
     })
 
     it('should not produce an error', function (done) {
-      return this.TokenAccessHandler.addReadAndWriteUserToProject(
+      this.TokenAccessHandler.addReadAndWriteUserToProject(
         this.userId,
         this.projectId,
         err => {
           expect(err).to.not.exist
-          return done()
+          done()
         }
       )
     })
 
     describe('when Project.updateOne produces an error', function () {
       beforeEach(function () {
-        return (this.Project.updateOne = sinon
+        this.Project.updateOne = sinon
           .stub()
-          .callsArgWith(2, new Error('woops')))
+          .callsArgWith(2, new Error('woops'))
       })
 
       it('should produce an error', function (done) {
-        return this.TokenAccessHandler.addReadAndWriteUserToProject(
+        this.TokenAccessHandler.addReadAndWriteUserToProject(
           this.userId,
           this.projectId,
           err => {
             expect(err).to.exist
-            return done()
+            done()
           }
         )
       })
@@ -241,7 +231,7 @@ describe('TokenAccessHandler', function () {
 
   describe('grantSessionTokenAccess', function () {
     beforeEach(function () {
-      return (this.req = { session: {}, headers: {} })
+      this.req = { session: {}, headers: {} }
     })
 
     it('should add the token to the session', function (done) {
@@ -253,7 +243,7 @@ describe('TokenAccessHandler', function () {
       expect(
         this.req.session.anonTokenAccess[this.projectId.toString()]
       ).to.equal(this.token)
-      return done()
+      done()
     })
   })
 
@@ -267,27 +257,28 @@ describe('TokenAccessHandler', function () {
       })
 
       it('should try to find projects with both kinds of token', function (done) {
-        return this.TokenAccessHandler.validateTokenForAnonymousAccess(
+        this.TokenAccessHandler.validateTokenForAnonymousAccess(
           this.projectId,
           this.token,
           (err, allowed) => {
+            expect(err).to.not.exist
             expect(
               this.TokenAccessHandler.getProjectByToken.callCount
             ).to.equal(1)
-            return done()
+            done()
           }
         )
       })
 
       it('should allow read-only access', function (done) {
-        return this.TokenAccessHandler.validateTokenForAnonymousAccess(
+        this.TokenAccessHandler.validateTokenForAnonymousAccess(
           this.projectId,
           this.token,
           (err, rw, ro) => {
             expect(err).to.not.exist
             expect(rw).to.equal(false)
             expect(ro).to.equal(true)
-            return done()
+            done()
           }
         )
       })
@@ -309,27 +300,28 @@ describe('TokenAccessHandler', function () {
         })
 
         it('should try to find projects with both kinds of token', function (done) {
-          return this.TokenAccessHandler.validateTokenForAnonymousAccess(
+          this.TokenAccessHandler.validateTokenForAnonymousAccess(
             this.projectId,
             this.token,
             (err, rw, ro) => {
+              expect(err).to.not.exist
               expect(
                 this.TokenAccessHandler.getProjectByToken.callCount
               ).to.equal(1)
-              return done()
+              done()
             }
           )
         })
 
         it('should not allow read-and-write access', function (done) {
-          return this.TokenAccessHandler.validateTokenForAnonymousAccess(
+          this.TokenAccessHandler.validateTokenForAnonymousAccess(
             this.projectId,
             this.token,
             (err, rw, ro) => {
               expect(err).to.not.exist
               expect(rw).to.equal(false)
               expect(ro).to.equal(false)
-              return done()
+              done()
             }
           )
         })
@@ -341,27 +333,28 @@ describe('TokenAccessHandler', function () {
         })
 
         it('should try to find projects with both kinds of token', function (done) {
-          return this.TokenAccessHandler.validateTokenForAnonymousAccess(
+          this.TokenAccessHandler.validateTokenForAnonymousAccess(
             this.projectId,
             this.token,
             (err, rw, ro) => {
+              expect(err).to.not.exist
               expect(
                 this.TokenAccessHandler.getProjectByToken.callCount
               ).to.equal(1)
-              return done()
+              done()
             }
           )
         })
 
         it('should allow read-and-write access', function (done) {
-          return this.TokenAccessHandler.validateTokenForAnonymousAccess(
+          this.TokenAccessHandler.validateTokenForAnonymousAccess(
             this.projectId,
             this.token,
             (err, rw, ro) => {
               expect(err).to.not.exist
               expect(rw).to.equal(true)
               expect(ro).to.equal(false)
-              return done()
+              done()
             }
           )
         })
@@ -376,27 +369,28 @@ describe('TokenAccessHandler', function () {
       })
 
       it('should try to find projects with both kinds of token', function (done) {
-        return this.TokenAccessHandler.validateTokenForAnonymousAccess(
+        this.TokenAccessHandler.validateTokenForAnonymousAccess(
           this.projectId,
           this.token,
           (err, allowed) => {
+            expect(err).to.not.exist
             expect(
               this.TokenAccessHandler.getProjectByToken.callCount
             ).to.equal(1)
-            return done()
+            done()
           }
         )
       })
 
       it('should not allow any access', function (done) {
-        return this.TokenAccessHandler.validateTokenForAnonymousAccess(
+        this.TokenAccessHandler.validateTokenForAnonymousAccess(
           this.projectId,
           this.token,
           (err, rw, ro) => {
             expect(err).to.not.exist
             expect(rw).to.equal(false)
             expect(ro).to.equal(false)
-            return done()
+            done()
           }
         )
       })
@@ -410,20 +404,22 @@ describe('TokenAccessHandler', function () {
       })
 
       it('should try to find projects with both kinds of token', function (done) {
-        return this.TokenAccessHandler.validateTokenForAnonymousAccess(
+        this.TokenAccessHandler.validateTokenForAnonymousAccess(
           this.projectId,
           this.token,
           (err, allowed) => {
+            expect(err).to.exist
+            expect(allowed).to.not.exist
             expect(
               this.TokenAccessHandler.getProjectByToken.callCount
             ).to.equal(1)
-            return done()
+            done()
           }
         )
       })
 
       it('should produce an error and not allow access', function (done) {
-        return this.TokenAccessHandler.validateTokenForAnonymousAccess(
+        this.TokenAccessHandler.validateTokenForAnonymousAccess(
           this.projectId,
           this.token,
           (err, rw, ro) => {
@@ -431,7 +427,7 @@ describe('TokenAccessHandler', function () {
             expect(err).to.be.instanceof(Error)
             expect(rw).to.equal(undefined)
             expect(ro).to.equal(undefined)
-            return done()
+            done()
           }
         )
       })
@@ -439,7 +435,7 @@ describe('TokenAccessHandler', function () {
 
     describe('when project is not set to token-based access', function () {
       beforeEach(function () {
-        return (this.project.publicAccesLevel = 'private')
+        this.project.publicAccesLevel = 'private'
       })
 
       describe('for read-and-write project', function () {
@@ -453,14 +449,14 @@ describe('TokenAccessHandler', function () {
         })
 
         it('should not allow any access', function (done) {
-          return this.TokenAccessHandler.validateTokenForAnonymousAccess(
+          this.TokenAccessHandler.validateTokenForAnonymousAccess(
             this.projectId,
             this.token,
             (err, rw, ro) => {
               expect(err).to.not.exist
               expect(rw).to.equal(false)
               expect(ro).to.equal(false)
-              return done()
+              done()
             }
           )
         })
@@ -477,14 +473,14 @@ describe('TokenAccessHandler', function () {
         })
 
         it('should not allow any access', function (done) {
-          return this.TokenAccessHandler.validateTokenForAnonymousAccess(
+          this.TokenAccessHandler.validateTokenForAnonymousAccess(
             this.projectId,
             this.token,
             (err, rw, ro) => {
               expect(err).to.not.exist
               expect(rw).to.equal(false)
               expect(ro).to.equal(false)
-              return done()
+              done()
             }
           )
         })
@@ -498,14 +494,14 @@ describe('TokenAccessHandler', function () {
         })
 
         it('should not allow any access', function (done) {
-          return this.TokenAccessHandler.validateTokenForAnonymousAccess(
+          this.TokenAccessHandler.validateTokenForAnonymousAccess(
             this.projectId,
             null,
             (err, rw, ro) => {
               expect(err).to.not.exist
               expect(rw).to.equal(false)
               expect(ro).to.equal(false)
-              return done()
+              done()
             }
           )
         })
@@ -515,21 +511,18 @@ describe('TokenAccessHandler', function () {
 
   describe('getDocPublishedInfo', function () {
     beforeEach(function () {
-      return (this.callback = sinon.stub())
+      this.callback = sinon.stub()
     })
 
     describe('when v1 api not set', function () {
       beforeEach(function () {
         this.settings.apis = { v1: undefined }
-        return this.TokenAccessHandler.getV1DocPublishedInfo(
-          this.token,
-          this.callback
-        )
+        this.TokenAccessHandler.getV1DocPublishedInfo(this.token, this.callback)
       })
 
       it('should not check access and return default info', function () {
         expect(this.V1Api.request.called).to.equal(false)
-        return expect(
+        expect(
           this.callback.calledWith(null, {
             allow: true,
           })
@@ -539,7 +532,7 @@ describe('TokenAccessHandler', function () {
 
     describe('when v1 api is set', function () {
       beforeEach(function () {
-        return (this.settings.apis = { v1: { url: 'v1Url' } })
+        this.settings.apis = { v1: { url: 'v1Url' } }
       })
 
       describe('on V1Api.request success', function () {
@@ -547,7 +540,7 @@ describe('TokenAccessHandler', function () {
           this.V1Api.request = sinon
             .stub()
             .callsArgWith(1, null, null, 'mock-data')
-          return this.TokenAccessHandler.getV1DocPublishedInfo(
+          this.TokenAccessHandler.getV1DocPublishedInfo(
             this.token,
             this.callback
           )
@@ -559,23 +552,21 @@ describe('TokenAccessHandler', function () {
               url: `/api/v1/sharelatex/docs/${this.token}/is_published`,
             })
           ).to.equal(true)
-          return expect(this.callback.calledWith(null, 'mock-data')).to.equal(
-            true
-          )
+          expect(this.callback.calledWith(null, 'mock-data')).to.equal(true)
         })
       })
 
       describe('on V1Api.request error', function () {
         beforeEach(function () {
           this.V1Api.request = sinon.stub().callsArgWith(1, 'error')
-          return this.TokenAccessHandler.getV1DocPublishedInfo(
+          this.TokenAccessHandler.getV1DocPublishedInfo(
             this.token,
             this.callback
           )
         })
 
         it('should callback with error', function () {
-          return expect(this.callback.calledWith('error')).to.equal(true)
+          expect(this.callback.calledWith('error')).to.equal(true)
         })
       })
     })
@@ -583,12 +574,12 @@ describe('TokenAccessHandler', function () {
 
   describe('getV1DocInfo', function () {
     beforeEach(function () {
-      return (this.callback = sinon.stub())
+      this.callback = sinon.stub()
     })
 
     describe('when v1 api not set', function () {
       beforeEach(function () {
-        return this.TokenAccessHandler.getV1DocInfo(
+        this.TokenAccessHandler.getV1DocInfo(
           this.token,
           this.v2UserId,
           this.callback
@@ -597,7 +588,7 @@ describe('TokenAccessHandler', function () {
 
       it('should not check access and return default info', function () {
         expect(this.V1Api.request.called).to.equal(false)
-        return expect(
+        expect(
           this.callback.calledWith(null, {
             exists: true,
             exported: false,
@@ -608,7 +599,7 @@ describe('TokenAccessHandler', function () {
 
     describe('when v1 api is set', function () {
       beforeEach(function () {
-        return (this.settings.apis = { v1: 'v1' })
+        this.settings.apis = { v1: 'v1' }
       })
 
       describe('on V1Api.request success', function () {
@@ -616,7 +607,7 @@ describe('TokenAccessHandler', function () {
           this.V1Api.request = sinon
             .stub()
             .callsArgWith(1, null, null, 'mock-data')
-          return this.TokenAccessHandler.getV1DocInfo(
+          this.TokenAccessHandler.getV1DocInfo(
             this.token,
             this.v2UserId,
             this.callback
@@ -629,16 +620,14 @@ describe('TokenAccessHandler', function () {
               url: `/api/v1/sharelatex/docs/${this.token}/info`,
             })
           ).to.equal(true)
-          return expect(this.callback.calledWith(null, 'mock-data')).to.equal(
-            true
-          )
+          expect(this.callback.calledWith(null, 'mock-data')).to.equal(true)
         })
       })
 
       describe('on V1Api.request error', function () {
         beforeEach(function () {
           this.V1Api.request = sinon.stub().callsArgWith(1, 'error')
-          return this.TokenAccessHandler.getV1DocInfo(
+          this.TokenAccessHandler.getV1DocInfo(
             this.token,
             this.v2UserId,
             this.callback
@@ -646,9 +635,67 @@ describe('TokenAccessHandler', function () {
         })
 
         it('should callback with error', function () {
-          return expect(this.callback.calledWith('error')).to.equal(true)
+          expect(this.callback.calledWith('error')).to.equal(true)
         })
       })
     })
   })
+
+  describe('createTokenHashPrefix', function () {
+    it('creates a prefix of the hash', function () {
+      const prefix =
+        this.TokenAccessHandler.createTokenHashPrefix('zxpxjrwdtsgd')
+      expect(prefix.length).to.equal(6)
+    })
+  })
+
+  describe('checkTokenHashPrefix', function () {
+    it('sends "match" to metrics when prefix matches the prefix of the hash of the token', function () {
+      const token = 'zxpxjrwdtsgd'
+      const prefix = this.TokenAccessHandler.createTokenHashPrefix(token)
+
+      this.TokenAccessHandler.checkTokenHashPrefix(token, prefix, 'readOnly')
+
+      expect(this.Metrics.inc).to.have.been.calledWith(
+        'link-sharing.hash-check',
+        {
+          path: 'readOnly',
+          status: 'match',
+        }
+      )
+    })
+    it('sends "mismatch" to metrics when prefix does not match the prefix of the hash of the token', function () {
+      const token = 'zxpxjrwdtsgd'
+      const prefix = this.TokenAccessHandler.createTokenHashPrefix(token)
+
+      this.TokenAccessHandler.checkTokenHashPrefix(
+        'anothertoken',
+        prefix,
+        'readOnly'
+      )
+
+      expect(this.Metrics.inc).to.have.been.calledWith(
+        'link-sharing.hash-check',
+        {
+          path: 'readOnly',
+          status: 'mismatch',
+        }
+      )
+    })
+    it('sends "missing" to metrics when prefix is undefined', function () {
+      this.TokenAccessHandler.checkTokenHashPrefix(
+        'anothertoken',
+        undefined,
+        'readOnly'
+      )
+
+      expect(this.Metrics.inc).to.have.been.calledWith(
+        'link-sharing.hash-check',
+        {
+          path: 'readOnly',
+          status: 'missing',
+        }
+      )
+    })
+  })
 })