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1. Standard Window Size and Placement

Window envelopes in India typically follow standardized dimensions and placements to ensure visibility of the address or relevant content while maintaining postal compliance.

• Common window sizes: 90 x 40 mm or 90 x 45 mm
  
• Windows usually placed on the front right side of the envelope, aligned to display the recipient’s address clearly
  
• Positioned approximately 15–20 mm from the bottom edge and 15–25 mm from the right edge
  
• Placement designed to fit A4 sheets folded into thirds (tri-fold) so the address shows without manual adjustment
  
• Windows should be aligned consistently for automated postal sorting
  

2. Window Material and Transparency

The window material needs to be clear enough for legibility but also durable and compliant with postal regulations.

• Typically made of transparent PVC or biodegradable cellulose films
  
• Should be anti-glare to enhance address readability under different lighting conditions
  
• Thickness ranges from 30 to 50 microns for durability without bulk
  
• Biodegradable or eco-friendly options are preferred for sustainability initiatives
  
• Material should securely adhere to the envelope and resist tearing during transit
  

3. Envelope Size Compatibility

Window envelopes are designed to fit standard paper sizes used in Indian correspondence, primarily A4.

• Common envelope sizes: DL (110 x 220 mm) and C5 (162 x 229 mm)
  
• DL envelopes accommodate tri-folded A4 sheets, ideal for invoices, official letters, and tender documents
  
• C5 envelopes fit A4 sheets folded in half, used for bulkier documents or brochures
  
• Envelope design ensures window placement matches the folded document’s address section
  

4. Printing and Design Guidelines Around the Window

Proper design ensures the window area does not interfere with branding or important information.

• Avoid printing logos, texts, or decorative elements too close to the window to prevent obstruction
  
• Leave a clear margin of at least 5 mm around the window inside and outside
  
• Use subtle branding (small logo or brand colors) positioned away from the window area
  
• Address fields on documents should be aligned precisely with the window position
  
• Ensure postal marks, barcodes, and stamps do not overlap the window or printed address
  

5. Security and Privacy Considerations

Window envelope design must safeguard recipient privacy and secure contents during mailing.

• Use opaque envelopes or tinted window films when sending sensitive or confidential documents
  
• Consider security tinting on the inside to obscure contents
  
• Windows should be positioned to minimize exposure of unnecessary information
  
• Employ tamper-evident seals or secure adhesive flaps for sensitive communications
  
• Design to comply with postal regulations and data privacy norms