When buying a vacuum cleaner online, you can consider things like: 1. Suction power: If you have carpets, a vacuum with good suction power can help remove pet hair. 2. Battery life: For robot vacuum cleaners, consider the battery capacity. A 5,000mAh battery can clean a 1,500 sq ft home. 3. Storage: If you have limited storage space, you can choose a handheld, upright, or vertical vacuum. 4. Capacity: A larger dust bag or cup means you won't need to change it as often. 5.Durability: Choose a vacuum made with high-quality materials that will last for years. 6. Water lift and airflow: These are important factors to consider when choosing a vacuum cleaner. 7. Design and structure: If the vacuum is on wheels, it shouldn't be too heavy for cleaning medium-small spaces. 8. Noise: Excessive noise can be a factor in your decision. 9 Filtration: A good filtration system can trap dust, allergens, and other particles