Font looks a little bolder on chrome

Its weird, when I use Source sans pro it looks bolder on chrome but when I switch to safari it looks thinner.

I have Source Sans downloaded so I don't have it embedded in the head

Not sure if its my code or my browser heres a piece of text in my code

            <div class="collapse navbar-collapse navHeaderCollapse">
            <ul class="nav navbar-nav navbar-right">
                <li><a href="#">HOME</a></li>
                <li><a href="#">MY WORK</a></li>
                <li><a href="#">ABOUT ME</a></li>

            </ul>
        </div>

CSS

ul{
font-family:'Source Sans Pro';
left: 50%;
position: absolute;
font-weight: 100;
letter-spacing: 0.5px;
font-size: 13px

}