Not a font
About The BrandInstagram is a mobile application designed for sharing photos and videos. Instagram was created by Kevin Systrom and Mike Krieger, and was launched in October of 2010.
What font does Instagram use?The original font used in Instagram's logo was Billabong which you can test with the font generator.
Instagram's current logo, which came out in 2013, uses a custom design made without a font. You can see it here.