{"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/layout/how-to-identify-layout-errors-caused-by-javascript-files.md","branch":"main","content":"> Tutorial valid only for Legacy CMS Stores.\n\nA way to identify whether an error appearing in the layout is caused by a VTEX standard control or by a Javascript file customized in the store is to use /tools.html.\n\nTo do so, follow the steps below:\n\n1. To disable the JS of the page, just add `/tools.html` at the end of the URL. E.g.: \\{AccountName\\}.myvtex.com/tools.html\n2. Click on __Disable__ in the __Client JavaScript is__ tab. \n\n![javascript-disable ](https://cdn.statically.io/gh/vtexdocs/help-center-content/refs/heads/main/docs/en/tutorials/storefront/layout/how-to-identify-layout-errors-caused-by-javascript-files_1.png)\n\n3. Next, remove `/tools.html` from the URL and update the page.\n\nIf the error displayed was caused by an external JavaScript file, it will no longer appear.\nThus, this file needs be adjusted.\n\nRegarding JS files inserted in the page, it is important to follow certain assumptions:\n\n- To use an external JS rather than online JavaScript.\n- To check whether it will interfere in the performance of the store.\n\nRemember that we also have the VTEX Speed tool that enables local development with shorter cache time. [Vtex Speed - Download e Execution](https://github.com/vtex/speed)\n\nTo investigate possible problems involving CSS, we recommend using the WebDeveloper plugin - look [here](/en/tutorial/tools-to-help-the-performance-of-your-e-commerce/) some tools to improve debugging customization issues."}