To set the responsive font size, use the ‘viewport width’ and set it to ‘vw’ unit. You can try to run the following code to use ‘vw’ unit −
Example
<!DOCTYPE html> <html> <head> <style> h1 { font-size:8vw; } </style> </head> <body> <h1>This is demo heading</h1> <p>This is demo text.</p> </body> </html>