diff --git a/.changeset/sharp-lies-shop.md b/.changeset/sharp-lies-shop.md
new file mode 100644
index 00000000..1c716fb3
--- /dev/null
+++ b/.changeset/sharp-lies-shop.md
@@ -0,0 +1,5 @@
+---
+"@changesets/action": patch
+---
+
+fix: Publish in custom artifactory #424 with `auth` or `authToken`
diff --git a/src/index.ts b/src/index.ts
index 194204dc..d4fd1a51 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -3,6 +3,7 @@ import fs from "fs-extra";
 import * as gitUtils from "./gitUtils";
 import { runPublish, runVersion } from "./run";
 import readChangesetState from "./readChangesetState";
+import { extractAuthTokenLine } from "./utils";
 
 const getOptionalInput = (name: string) => core.getInput(name) || undefined;
 
@@ -59,10 +60,7 @@ const getOptionalInput = (name: string) => core.getInput(name) || undefined;
       if (fs.existsSync(userNpmrcPath)) {
         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);
-        });
+        const authLine = extractAuthTokenLine(userNpmrcContent);
         if (authLine) {
           core.info(
             "Found existing auth token for the npm registry in the user .npmrc file"
diff --git a/src/utils.test.ts b/src/utils.test.ts
index 1633b891..aac6bba7 100644
--- a/src/utils.test.ts
+++ b/src/utils.test.ts
@@ -1,4 +1,4 @@
-import { getChangelogEntry, BumpLevels, sortTheThings } from "./utils";
+import { getChangelogEntry, BumpLevels, sortTheThings, extractAuthTokenLine } from "./utils";
 
 let changelog = `# @keystone-alpha/email
 
@@ -99,3 +99,97 @@ test("it sorts the things right", () => {
   ];
   expect(things.sort(sortTheThings)).toMatchSnapshot();
 });
+
+/**
+ * Test the extractAuthTokenLine function for various registries.
+ */
+describe("extractAuthTokenLine", () => {
+  it("should correctly find the auth token line for multiple registries", () => {
+    const testCases = [
+      {
+        name: "Custom private registry with _authToken",
+        npmrc: `
+          registry=https://custom.private-registry.com/api/npm/npm/
+          //custom.private-registry.com/api/npm/npm/:_authToken=abcd1234
+          always-auth=true
+        `,
+        expected: "//custom.private-registry.com/api/npm/npm/:_authToken=abcd1234",
+      },
+      {
+        name: "Custom private registry with _auth",
+        npmrc: `
+          registry=https://custom.private-registry.com/api/npm/npm/
+          //custom.private-registry.com/api/npm/npm/:_auth=abcd1234
+          always-auth=true
+        `,
+        expected: "//custom.private-registry.com/api/npm/npm/:_auth=abcd1234",
+      },
+      {
+        name: "NPM default registry with _authToken",
+        npmrc: `
+          registry=https://registry.npmjs.org/
+          //registry.npmjs.org/:_authToken=efgh5678
+        `,
+        expected: "//registry.npmjs.org/:_authToken=efgh5678",
+      },
+      {
+        name: "NPM default registry with _auth",
+        npmrc: `
+          registry=https://registry.npmjs.org/
+          //registry.npmjs.org/:_auth=efgh5678
+        `,
+        expected: "//registry.npmjs.org/:_auth=efgh5678",
+      },
+      {
+        name: "AWS CodeArtifact registry with _authToken",
+        npmrc: `
+          registry=https://mydomain-111122223333.d.codeartifact.us-east-1.amazonaws.com/npm/repository-name/
+          //mydomain-111122223333.d.codeartifact.us-east-1.amazonaws.com/npm/repository-name/:_authToken=ijkl9012
+        `,
+        expected:
+          "//mydomain-111122223333.d.codeartifact.us-east-1.amazonaws.com/npm/repository-name/:_authToken=ijkl9012",
+      },
+      {
+        name: "AWS CodeArtifact registry with _auth",
+        npmrc: `
+          registry=https://mydomain-111122223333.d.codeartifact.us-east-1.amazonaws.com/npm/repository-name/
+          //mydomain-111122223333.d.codeartifact.us-east-1.amazonaws.com/npm/repository-name/:_auth=ijkl9012
+        `,
+        expected:
+          "//mydomain-111122223333.d.codeartifact.us-east-1.amazonaws.com/npm/repository-name/:_auth=ijkl9012",
+      },
+      {
+        name: "Azure DevOps registry with _authToken",
+        npmrc: `
+          registry=https://pkgs.dev.azure.com/myorg/_packaging/myfeed/npm/registry/
+          //pkgs.dev.azure.com/myorg/_packaging/myfeed/npm/registry/:_authToken=mnop3456
+        `,
+        expected:
+          "//pkgs.dev.azure.com/myorg/_packaging/myfeed/npm/registry/:_authToken=mnop3456",
+      },
+      {
+        name: "Azure DevOps registry with _auth",
+        npmrc: `
+          registry=https://pkgs.dev.azure.com/myorg/_packaging/myfeed/npm/registry/
+          //pkgs.dev.azure.com/myorg/_packaging/myfeed/npm/registry/:_auth=mnop3456
+        `,
+        expected:
+          "//pkgs.dev.azure.com/myorg/_packaging/myfeed/npm/registry/:_auth=mnop3456",
+      },
+    ];
+
+    testCases.forEach(({ name, npmrc, expected }) => {
+      const result = extractAuthTokenLine(npmrc);
+      expect(result).toBe(expected);
+    });
+  });
+
+  it("should return undefined if no auth token line is present", () => {
+    const npmrcContent = `
+      registry=https://custom.private-registry.com/api/npm/npm/
+      always-auth=true
+    `;
+    const result = extractAuthTokenLine(npmrcContent);
+    expect(result).toBeUndefined();
+  });
+});
\ No newline at end of file
diff --git a/src/utils.ts b/src/utils.ts
index e92a1953..2f86b492 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -98,3 +98,20 @@ export function sortTheThings(
   }
   return -1;
 }
+
+/**
+ * Extracts the line containing the auth token from .npmrc content.
+ * 
+ * @param {string} npmrcContent - The content of the .npmrc file as a string.
+ * @returns {string | undefined} - The line containing the auth token or undefined if not found.
+ */
+export function extractAuthTokenLine(npmrcContent: string) {
+  /**
+   * @see https://github.com/npm/cli/blob/8f8f71e4dd5ee66b3b17888faad5a7bf6c657eed/test/lib/adduser.js#L103-L105
+   * This regex dynamically adapts to any registry by looking for the :_auth or :_authToken= pattern.
+   */
+  const line = npmrcContent.split("\n").find((line) => {
+    return /^\s*\/\/.*\/:(_auth|_authToken)=/i.test(line); // Match both _auth and _authToken
+  });
+  return line ? line.trim() : undefined;
+};
\ No newline at end of file