• Size: 45mm by 35mm. (514 Pixels x 400 Pixels)
• Color: Color only. ...
• Head size and position: Head should measure 25mm to 35mm. ...
• Recency: Taken within the last three months.
• Background: Solid white. ...
• Smile: Neutral expression only. ...
• Eyes: Visible and open.
• Glasses: Only if worn normally.
• Format: jpg, png 
• Max file size: 2MB

https://www.ica.gov.sg/photo-guidelines