diff --git a/ghost/core/core/server/services/mentions/ResourceService.js b/ghost/core/core/server/services/mentions/ResourceService.js
new file mode 100644
index 0000000000..2d2a5a467e
--- /dev/null
+++ b/ghost/core/core/server/services/mentions/ResourceService.js
@@ -0,0 +1,45 @@
+const ObjectID = require('bson-objectid').default;
+
+/**
+ * @typedef {import('@tryghost/webmentions/lib/MentionsAPI').IResourceService} IResourceService
+ */
+
+/**
+ * @implements {IResourceService}
+ */
+module.exports = class ResourceService {
+    /** @type {import('@tryghost/url-utils/lib/url-utils')} */
+    #urlUtils;
+
+    /** @type {import('../url')} */
+    #urlService;
+
+    /**
+     * @param {object} deps
+     * @param {import('@tryghost/url-utils/lib/url-utils')} deps.urlUtils
+     * @param {import('../url')} deps.urlService
+     */
+    constructor(deps) {
+        this.#urlUtils = deps.urlUtils;
+        this.#urlService = deps.urlService;
+    }
+
+    /**
+     * @param {URL} url
+     * @returns {Promise<import('@tryghost/webmentions/lib/MentionsAPI').ResourceResult>}
+     */
+    async getByURL(url) {
+        const path = this.#urlUtils.absoluteToRelative(url.href, {withoutSubdirectory: true});
+        const resource = this.#urlService.getResource(path);
+        if (resource?.config?.type === 'posts') {
+            return {
+                type: 'post',
+                id: ObjectID.createFromHexString(resource.data.id)
+            };
+        }
+        return {
+            type: null,
+            id: null
+        };
+    }
+};
diff --git a/ghost/core/core/server/services/mentions/service.js b/ghost/core/core/server/services/mentions/service.js
index 58e2d2d2ee..cd6e4af202 100644
--- a/ghost/core/core/server/services/mentions/service.js
+++ b/ghost/core/core/server/services/mentions/service.js
@@ -1,4 +1,3 @@
-const ObjectID = require('bson-objectid').default;
 const MentionController = require('./MentionController');
 const WebmentionMetadata = require('./WebmentionMetadata');
 const {
@@ -7,6 +6,7 @@ const {
     MentionDiscoveryService
 } = require('@tryghost/webmentions');
 const BookshelfMentionRepository = require('./BookshelfMentionRepository');
+const ResourceService = require('./ResourceService');
 const RoutingService = require('./RoutingService');
 
 const models = require('../../models');
@@ -30,6 +30,10 @@ module.exports = {
         });
         const webmentionMetadata = new WebmentionMetadata();
         const discoveryService = new MentionDiscoveryService({externalRequest});
+        const resourceService = new ResourceService({
+            urlUtils,
+            urlService
+        });
         const routingService = new RoutingService({
             siteUrl: new URL(urlUtils.getSiteUrl())
         });
@@ -37,22 +41,7 @@ module.exports = {
         const api = new MentionsAPI({
             repository,
             webmentionMetadata,
-            resourceService: {
-                async getByURL(url) {
-                    const path = urlUtils.absoluteToRelative(url.href, {withoutSubdirectory: true});
-                    const resource = urlService.getResource(path);
-                    if (resource?.config?.type === 'posts') {
-                        return {
-                            type: 'post',
-                            id: ObjectID.createFromHexString(resource.data.id)
-                        };
-                    }
-                    return {
-                        type: null,
-                        id: null
-                    };
-                }
-            },
+            resourceService,
             routingService
         });
 
diff --git a/ghost/core/test/unit/server/services/mentions/ResourceService.test.js b/ghost/core/test/unit/server/services/mentions/ResourceService.test.js
new file mode 100644
index 0000000000..9c8ce64f4d
--- /dev/null
+++ b/ghost/core/test/unit/server/services/mentions/ResourceService.test.js
@@ -0,0 +1,128 @@
+const assert = require('assert');
+const sinon = require('sinon');
+const ResourceService = require('../../../../../core/server/services/mentions/ResourceService');
+const UrlUtils = require('@tryghost/url-utils');
+const UrlService = require('../../../../../core/server/services/url/UrlService');
+
+function stubGetResource(urlService) {
+    const getResource = sinon.stub(urlService, 'getResource');
+
+    getResource.withArgs('/post-resource').returns({
+        config: {
+            type: 'posts'
+        },
+        data: {
+            id: '63ce473f992390b739b00b01'
+        }
+    });
+
+    getResource.withArgs('/tag-resource').returns({
+        config: {
+            type: 'tags'
+        },
+        data: {
+            id: '63ce473f992390b739b00b02'
+        }
+    });
+
+    getResource.withArgs('/no-resource').returns(null);
+
+    return getResource;
+}
+
+describe('ResourceService', function () {
+    describe('getByURL', function () {
+        it('Correctly converts post resources', async function () {
+            const urlUtils = new UrlUtils({
+                getSiteUrl() {
+                    return 'https://site.com/blah/';
+                },
+                getSubdir() {
+                    return '/blah';
+                },
+                getAdminUrl() {
+                    return 'https://admin.com';
+                }
+            });
+
+            const urlService = new UrlService();
+            const resourceService = new ResourceService({
+                urlUtils,
+                urlService
+            });
+
+            const getResource = stubGetResource(urlService);
+
+            const result = await resourceService.getByURL(
+                new URL('https://site.com/blah/post-resource')
+            );
+
+            assert(getResource.calledWithExactly('/post-resource'));
+
+            assert.equal(result.type, 'post');
+            assert.equal(result.id.toHexString(), '63ce473f992390b739b00b01');
+        });
+
+        it('Does not convert tag resources', async function () {
+            const urlUtils = new UrlUtils({
+                getSiteUrl() {
+                    return 'https://site.com/blah/';
+                },
+                getSubdir() {
+                    return '/blah';
+                },
+                getAdminUrl() {
+                    return 'https://admin.com';
+                }
+            });
+
+            const urlService = new UrlService();
+            const resourceService = new ResourceService({
+                urlUtils,
+                urlService
+            });
+
+            const getResource = stubGetResource(urlService);
+
+            const result = await resourceService.getByURL(
+                new URL('https://site.com/blah/tag-resource')
+            );
+
+            assert(getResource.calledWithExactly('/tag-resource'));
+
+            assert.equal(result.type, null);
+            assert.equal(result.id, null);
+        });
+
+        it('Handles non-resources', async function () {
+            const urlUtils = new UrlUtils({
+                getSiteUrl() {
+                    return 'https://site.com/blah/';
+                },
+                getSubdir() {
+                    return '/blah';
+                },
+                getAdminUrl() {
+                    return 'https://admin.com';
+                }
+            });
+
+            const urlService = new UrlService();
+            const resourceService = new ResourceService({
+                urlUtils,
+                urlService
+            });
+
+            const getResource = stubGetResource(urlService);
+
+            const result = await resourceService.getByURL(
+                new URL('https://site.com/blah/no-resource')
+            );
+
+            assert(getResource.calledWithExactly('/no-resource'));
+
+            assert.equal(result.type, null);
+            assert.equal(result.id, null);
+        });
+    });
+});