Whatsapp Web is a Whatsapp client with a frontend in HTML, CSS and JS. If you are using it in a browser or in a service collector and you want use it in a small window while maintaining a good levels of usability you can inject this CSS into your browser's tab or service.
Up to 900px wide the chat list is shown with the profile photos of the contacts, only if you hover over the list the message preview appears and the chat space occupies the remaining space. Above 900px the UI is the default interface.
@media screen and (max-width: 900px)
{
._1XkO3
{
min-width: 500px !important;
}
.two ._3RGKj
{
flex: 0 0 80px !important;
max-width: 80px !important;
}
.two:hover ._3RGKj:hover
{
flex: 0 0 45% !important;
max-width: 45% !important;
}
.uwk68,
.dsh4tgtl.e1gr2w1z.bsvz8e3l.hmy10g0s.cw3vfol9,
._3yZPA,
._1Yy79._1-SiY,
._3OvU8
{
display: none !important;
}
.two:hover ._3RGKj:hover > ._1KDb8 > .uwk68,
.two:hover ._3RGKj:hover > ._1KDb8 > div > div > div > .dsh4tgtl.e1gr2w1z.bsvz8e3l.hmy10g0s.cw3vfol9,
.two:hover ._3RGKj:hover > header >._3yZPA,
.two:hover ._3RGKj:hover > span > div > div > ._1Yy79._1-SiY,
.two:hover ._3RGKj:hover > div > div > div > div > div > div > div > div > div > ._3OvU8
{
display: block !important;
}
}