You can use SignRequest on all devices (phones, tablets, laptops or desktops).
On devices with Internet Explorer 8 or earlier the service might not work as smoothly as on others, but even Microsoft doesn't support these versions anymore.
If you believe your signature doesn't look good enough we recommend using a mobile device to create your signature. If you log in on a mobile device the signature will be accessible on your other devices as well. (You might have to refresh the page.)