Blue lines/edges in edit mode

[Wojofoo]

Can anyone tell me what the blue lines represent in Blender? I tried googling for an answer but couldn’t find anything.

Thanks!

[Stan_Pancakes (Stanislav Blinov)]

Those are edges marked as “Sharp”. They’re used with smooth shading to designate shading seams.

If you want to get rid of it, select all, Mesh -> Edges -> Clear Sharp.

[Modron]

if you’re going to subsurf, you’ll need some attention to topology, especially keeping tight edge loops around the edges and corners.