Reduce image file sizes and lower transfer costs by adjusting image quality through Alibaba Cloud CDN's image editing feature. Quality adjustment supports two methods: automatic compression, and URL-based quality parameters.
The image editing feature of Alibaba Cloud CDN, the image editing feature of Dynamic Content Delivery Network (DCDN), and the Image Processing (IMG) feature of Object Storage Service (OSS) are three separate features and cannot be used interchangeably.
Image editing is a paid service and is free of charge until further notice.
Automatic compression
Automatic compression reduces file size without changing image dimensions or format. For setup instructions, see Enable and use image editing.
Quality parameters
Quality transformation applies only to JPG and WebP images. Set the action to quality and use one of the following parameters.
Parameter reference
Parameter | Description | Valid values |
| Absolute quality value. Sets a quality ceiling — output quality is whichever is lower: the target value or the original quality. Quality can only be lowered, not raised. | Multiples of 5 in the range 0–100 (other values are not supported). Higher values produce better quality and sharpness. 95 is recommended. |
| Quality coefficient. Multiplies the original quality by the specified percentage to calculate the output quality. | Multiples of 5 in the range 0–100 (other values are not supported). Higher values produce better quality and sharpness. 95 is recommended. |
Examples
Absolute quality (`Q`)
http(s)://example.com/image01.jpg?image_process=quality,Q_90Q sets a quality ceiling. If the original quality is already below the target value, the original quality is kept.
Original quality | Target ( | Output quality |
95 | 90 | 90 (reduced to target) |
80 | 90 | 80 (original kept — cannot increase) |
Quality coefficient (`q`)
http(s)://example.com/image01.jpg?image_process=quality,q_90q scales quality relative to the original. The output quality equals the original quality multiplied by the coefficient.
Original quality | Coefficient ( | Output quality |
80 | 90% | 80 × 90% = 72 |