<!DOCTYPE html> <html style="font-size: 16px"> <head> <meta name="viewport" content="width=800"> <style> body { width: 800px; margin: 0; overflow-y: hidden; } </style> <script src="resources/autosizingTest.js"></script> </head> <body> <section contenteditable="true"> The text inside this textarea should be autosized to 40px computed font-size (16 * 800/320). </section> </body> </html>