---
title: A/B testing with same-URL direct access
description: Set up an A/B test by controlling what response is served based on cookies.
image: https://developers.cloudflare.com/core-services-preview.png
---

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# A/B testing with same-URL direct access

Set up an A/B test by controlling what response is served based on cookies.

This version passes through requests for `/test/*` and `/control/*` URI paths to the origin server, bypassing random assignment.

JavaScript

```
const NAME = "myExampleABTest";
export default {  async fetch(request) {    // Clone the original URL    const url = new URL(request.url);
    // Enable Passthrough to allow direct access to control and test routes.    if (url.pathname.startsWith("/control") || url.pathname.startsWith("/test"))      return fetch(request);
    // Determine which group this requester is in.    const cookie = request.headers.get("cookie");
    if (cookie && cookie.includes(`${NAME}=control`)) {      url.pathname = "/control" + url.pathname;    } else if (cookie && cookie.includes(`${NAME}=test`)) {      url.pathname = "/test" + url.pathname;    } else {      // If there is no cookie, this is a new client. Choose a group and set the cookie.      const group = Math.random() < 0.5 ? "test" : "control"; // 50/50 split      if (group === "control") {        url.pathname = "/control" + url.pathname;      } else {        url.pathname = "/test" + url.pathname;      }      // Reconstruct response to avoid immutability      let response = await fetch(url);      response = new Response(response.body, response);      // Set cookie to enable persistent A/B sessions.      response.headers.append("Set-Cookie", `${NAME}=${group}; path=/`);      return response;    }    return fetch(url);  },};
```

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```