Helvetica has been Facebook's font of choice for a long time, but some keen-eyed users noticed a slight change while browsing their news feeds Friday. Facebook is testing out a new, thinner font for some desktop users, and it's called Geneva.

Here's a look at the new font vs. the old:

Take a look at some key letters like the lowercase "a" and uppercase "G," each of which has clear differences between the old font and the new. You can also see that the new links appear to be a darker blue than the old links, while the body text is a little lighter.

The new font appears to be only visible to desktop users, at least for now. 

Mashablehas contacted Facebook about the new font, and we'll update this story when we have information about whether the font change is permanent or just a test. Websites and services often try out new fonts and colors for some users to see if it has any effect on engagement. Recently Google tried testing black-colored links instead of blue, a test that barely lasted a day. We could all go back to seeing posts in Helvetica before we know it.

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