Improved referrer parser matching on direct (internal) traffic (#536)

ref https://linear.app/ghost/issue/PROD-1960/

Updated referrer parsing matching on site domain such that internal traffic is more consistently identified as 'direct'/internal, rather than treating it as a referrer w/ a source.

Author: 9larsons

packages/referrer-parser/lib/ReferrerParser.ts

@@ -186,12 +186,29 @@ export class ReferrerParser {
                 return false;
             }
 
-            if (this.siteUrl.hostname === url.hostname) {
+            // Handle subdomain variations (www.example.com vs example.com)
+            const siteHostname = this.siteUrl.hostname;
+            const urlHostname = url.hostname;
+            
+            // Check for exact match first
+            if (siteHostname === urlHostname) {
                 if (url.pathname.startsWith(this.siteUrl.pathname)) {
                     return true;
                 }
                 return false;
             }
+            
+            // Check for www subdomain variations
+            const siteWithoutWww = siteHostname.replace(/^www\./, '');
+            const urlWithoutWww = urlHostname.replace(/^www\./, '');
+            
+            if (siteWithoutWww === urlWithoutWww) {
+                if (url.pathname.startsWith(this.siteUrl.pathname)) {
+                    return true;
+                }
+                return false;
+            }
+            
             return false;
         } catch (e) {
             return false;

packages/referrer-parser/test/ReferrerParser.test.ts

@@ -227,6 +227,20 @@ describe('ReferrerParser', () => {
             assertPropertyEquals(result, 'referrerMedium', null);
             assertPropertyEquals(result, 'referrerUrl', null);
         });
+
+        it('identifies internal traffic for subdomain variations (regression test for levernews.com)', () => {
+            // Test case: site configured as www.levernews.com, referrer is levernews.com
+            // This should return null values (internal traffic) instead of showing levernews.com as referrerSource
+            const leverParser = new ReferrerParser({
+                siteUrl: 'https://www.levernews.com'
+            });
+            
+            const result = leverParser.parse('https://levernews.com/article');
+            should.exist(result);
+            assertPropertyEquals(result, 'referrerSource', null);
+            assertPropertyEquals(result, 'referrerMedium', null);
+            assertPropertyEquals(result, 'referrerUrl', null);
+        });
     });
 
     describe('getDataFromUrl', () => {
@@ -344,6 +358,40 @@ describe('ReferrerParser', () => {
             const result = parser.isSiteDomain({} as URL);
             should.equal(result, false);
         });
+
+        it('handles www subdomain variations', () => {
+            // Test www.example.com configured, levernews.com referrer
+            const parser1 = new ReferrerParser({
+                siteUrl: 'https://www.levernews.com'
+            });
+            const url1 = new URL('https://levernews.com/article');
+            const result1 = parser1.isSiteDomain(url1);
+            should.equal(result1, true);
+
+            // Test levernews.com configured, www.levernews.com referrer
+            const parser2 = new ReferrerParser({
+                siteUrl: 'https://levernews.com'
+            });
+            const url2 = new URL('https://www.levernews.com/article');
+            const result2 = parser2.isSiteDomain(url2);
+            should.equal(result2, true);
+
+            // Test both with www
+            const parser3 = new ReferrerParser({
+                siteUrl: 'https://www.levernews.com'
+            });
+            const url3 = new URL('https://www.levernews.com/article');
+            const result3 = parser3.isSiteDomain(url3);
+            should.equal(result3, true);
+
+            // Test both without www
+            const parser4 = new ReferrerParser({
+                siteUrl: 'https://levernews.com'
+            });
+            const url4 = new URL('https://levernews.com/article');
+            const result4 = parser4.isSiteDomain(url4);
+            should.equal(result4, true);
+        });
     });
 
     describe('isGhostNewsletter', () => {