diff --git a/src/index.ts b/src/index.ts
index 31aef207..5601b09a 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -60,8 +60,10 @@ const getOptionalInput = (name: string) => core.getInput(name) || undefined;
         core.info("Found existing user .npmrc file");
         const userNpmrcContent = await fs.readFile(userNpmrcPath, "utf8");
         const authLine = userNpmrcContent.split("\n").find((line) => {
-          // check based on https://github.com/npm/cli/blob/8f8f71e4dd5ee66b3b17888faad5a7bf6c657eed/test/lib/adduser.js#L103-L105
-          return /^\s*\/\/registry\.npmjs\.org\/:[_-]authToken=/i.test(line);
+          // npm registry format: https://github.com/npm/cli/blob/8f8f71e4dd5ee66b3b17888faad5a7bf6c657eed/test/lib/adduser.js#L103-L105
+          // github registry format: https://docs.github.com/en/packages/working-with-a-github-packages-registry/working-with-the-npm-registry#authenticating-with-a-personal-access-token
+          // also allow support for custom domain format, eg: //code.org.com/packages/npm/:_authToken=
+          return /:[_-]authToken=/i.test(line);
         });
         if (authLine) {
           core.info(