{"section":"tutorials","requestedLocale":"en","requestedSlug":"how-to-identify-layout-errors-caused-by-javascript-files","locale":"en","slug":"how-to-identify-layout-errors-caused-by-javascript-files","path":"docs/en/tutorials/storefront/cms-portal-legacy/layout/how-to-identify-layout-errors-caused-by-javascript-files.md","branch":"main","content":"> ⚠️ This tutorial is only valid for CMS Portal (Legacy) stores.\n\nYou can use the `/tools.html` page to check whether a layout error comes from a custom JavaScript file in the store or from native VTEX behavior.\n\nTo disable client JavaScript and test the page, follow the steps below:\n\n1. Go to `https://{accountName}.myvtex.com/tools.html`, replacing `{accountName}` with your store's account name.\n2. In the **Client JavaScript is** tab, click **Disable**.\n\n![tools.html page with the option to disable client JavaScript](https://cdn.statically.io/gh/vtexdocs/help-center-content/refs/heads/main/docs/en/tutorials/storefront/cms-portal-legacy/layout/how-to-identify-layout-errors-caused-by-javascript-files_1.png)\n\n3. Remove `/tools.html` from the URL and refresh the store page.\n\nIf the error disappears, it is likely caused by a custom JavaScript file. In that case, update the file.\n\nWhen adding JavaScript to the page, follow these recommendations:\n\n- Use an external JavaScript file, not inline code.\n- Check that the file does not affect store performance."}