diff --git a/packages/element-web-playwright-common/src/index.ts b/packages/element-web-playwright-common/src/index.ts
index 4f13e8be..cffc4466 100644
--- a/packages/element-web-playwright-common/src/index.ts
+++ b/packages/element-web-playwright-common/src/index.ts
@@ -9,6 +9,9 @@ Please see LICENSE files in the repository root for full details.
 import { type Config as BaseConfig } from "@element-hq/element-web-module-api";
 
 import { test as base } from "./fixtures/index.js";
+import { routeConfigJson } from "./utils/config_json.js";
+
+export * from "./utils/config_json.js";
 
 // Enable experimental service worker support
 // See https://playwright.dev/docs/service-workers-experimental#how-to-enable
@@ -68,32 +71,7 @@ export const test = base.extend<TestFixtures>({
     labsFlags: async ({}, use) => use([]),
     disablePresence: async ({}, use) => use(false),
     page: async ({ homeserver, context, page, config, labsFlags, disablePresence }, use) => {
-        await context.route(`http://localhost:8080/config.json*`, async (route) => {
-            const json = {
-                ...CONFIG_JSON,
-                ...config,
-                default_server_config: {
-                    "m.homeserver": {
-                        base_url: homeserver.baseUrl,
-                    },
-                    ...config.default_server_config,
-                },
-            };
-            json["features"] = {
-                ...json["features"],
-                // Enable the lab features
-                ...labsFlags.reduce<NonNullable<(typeof CONFIG_JSON)["features"]>>((obj, flag) => {
-                    obj[flag] = true;
-                    return obj;
-                }, {}),
-            };
-            if (disablePresence) {
-                json["enable_presence_by_hs_url"] = {
-                    [homeserver.baseUrl]: false,
-                };
-            }
-            await route.fulfill({ json });
-        });
+        await routeConfigJson(context, homeserver.baseUrl, config, labsFlags, disablePresence);
         await use(page);
     },
 });
diff --git a/packages/element-web-playwright-common/src/utils/config_json.ts b/packages/element-web-playwright-common/src/utils/config_json.ts
new file mode 100644
index 00000000..f2a98f47
--- /dev/null
+++ b/packages/element-web-playwright-common/src/utils/config_json.ts
@@ -0,0 +1,71 @@
+/*
+Copyright 2025 New Vector Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE files in the repository root for full details.
+*/
+
+import { BrowserContext, Page } from "@playwright/test";
+
+import { Config, CONFIG_JSON } from "../index.js";
+
+/** Construct a suitable config.json for the given homeserver
+ *
+ * @param homeserverBaseUrl - The `baseUrl` of the homeserver that the client should be configured to connect to.
+ * @param additionalConfig - Additional config to add to the default config.json.
+ * @param labsFlags - Lab flags to enable in the client.
+ * @param disablePresence - Whether to disable presence for the given homeserver.
+ */
+export function buildConfigJson(
+    homeserverBaseUrl: string,
+    additionalConfig: Partial<Config> = {},
+    labsFlags: string[] = [],
+    disablePresence: boolean = false,
+): Partial<Config> {
+    const json = {
+        ...CONFIG_JSON,
+        ...additionalConfig,
+        default_server_config: {
+            "m.homeserver": {
+                base_url: homeserverBaseUrl,
+            },
+            ...additionalConfig.default_server_config,
+        },
+    };
+    json["features"] = {
+        ...json["features"],
+        // Enable the lab features
+        ...labsFlags.reduce<NonNullable<(typeof CONFIG_JSON)["features"]>>((obj, flag) => {
+            obj[flag] = true;
+            return obj;
+        }, {}),
+    };
+    if (disablePresence) {
+        json["enable_presence_by_hs_url"] = {
+            [homeserverBaseUrl]: false,
+        };
+    }
+    return json;
+}
+
+/**
+ * Add a route to the browser context/page which will serve a suitable config.json for the given homeserver.
+ *
+ * @param context - The browser context or page to route the config.json to.
+ * @param homeserverBaseUrl - The `baseUrl` of the homeserver that the client should be configured to connect to.
+ * @param additionalConfig - Additional config to add to the default config.json.
+ * @param labsFlags - Lab flags to enable in the client.
+ * @param disablePresence - Whether to disable presence for the given homeserver.
+ */
+export async function routeConfigJson(
+    context: BrowserContext | Page,
+    homeserverBaseUrl: string,
+    additionalConfig: Partial<Config> = {},
+    labsFlags: string[] = [],
+    disablePresence: boolean = false,
+): Promise<void> {
+    await context.route(`http://localhost:8080/config.json*`, async (route) => {
+        const json = buildConfigJson(homeserverBaseUrl, additionalConfig, labsFlags, disablePresence);
+        await route.fulfill({ json });
+    });
+}