Only clean the glass when it is completely cool. Use a specialized fireplace glass cleaner; avoid ammonia-based products (like Windex), which can bake onto the glass and cause permanent etching.
Standard tempered glass is rated for roughly 400°F–500°F. Ceramic glass (often branded as PyroCeram or Robax) can withstand continuous temperatures up to 1,200°F–1,400°F . buy ceramic glass fireplace doors
The biggest difference lies in heat tolerance and transparency: Only clean the glass when it is completely cool