Glass is never perfectly clear or transparent in the real world. Adding procedural surface imperfections, smudges, scratches will improve realism. This shader is fully adjustable with easily adjusted settings.

Features: 

• Add smudges with adjustable detail level, size and amount of smudges.
• Easily adjustable controls for surface imperfections
• Procedural bump map to add extra detail and realism
• No uv unwrapping is required, since it's procedural it can be applied to any model. 
• Shader is eevee ready and also functions in Cycles.
• Color of glass and Ior value can be adjusted within the shader.