Compression levels explained with clear impact on quality and file size.
This guide explains the available compression levels in Robin Image Optimizer and how each level affects image quality and file size. It is intended to help you choose the right compression mode based on your use case.
How image compression works
Image compression reduces file size by removing unnecessary or less noticeable data from images. The stronger the compression, the smaller the file size, but this can also reduce image quality.
Robin Image Optimizer offers multiple compression levels so you can control the balance between quality and performance.
Lossless compression
What it does
Lossless compression reduces file size without removing visible image data. The visual quality of the image remains unchanged.
Impact on quality
No visible quality loss.
Impact on file size
Moderate reduction. File sizes are usually reduced by around 30 to 50 percent.
When to use it
Recommended for most websites, especially:
- Photography portfolios
- Design focused sites
- E commerce product images
- Any site where image quality is critical
Lossy compression
What it does
Lossy compression removes some image data that is less noticeable to the human eye in order to achieve smaller file sizes.
Impact on quality
Minor quality loss. In most cases the difference is not noticeable at normal viewing sizes.
Impact on file size
Higher reduction than lossless. File sizes are usually reduced by around 50 to 70 percent.
When to use it
Good choice for:
- Blogs and content heavy sites
- Marketing pages
- Sites where performance is more important than pixel perfect quality
High compression
What it does
Applies aggressive compression to minimize file size as much as possible.
Impact on quality
Noticeable quality loss may occur, especially on large or detailed images.
Impact on file size
Very high reduction. File sizes can be reduced by 70 percent or more.
When to use it
Suitable for:
- Image heavy sites
- Sites targeting very low bandwidth connections
- Non critical visuals such as backgrounds or decorative images
G PageSpeed mode
What it does
Optimizes images to better align with Google PageSpeed Insights recommendations.
Impact on quality
Balanced. Quality loss is minimal but more aggressive than standard lossy compression.
Impact on file size
High reduction while keeping images visually acceptable.
When to use it
Recommended if:
- You are actively optimizing for PageSpeed scores
- Performance metrics are a priority
- You want a balance between quality and speed
Custom compression
What it does
Allows you to fine tune compression settings manually.
Impact on quality and file size
Depends on the selected values. Gives full control over the tradeoff between quality and size.
When to use it
Best for advanced users who:
- Have specific quality requirements
- Want consistent compression across all images
- Have tested different compression levels
Choosing the right compression level
As a general guideline:
- Start with Lossless for production sites
- Switch to Lossy if file size reduction is not sufficient
- Use G PageSpeed when optimizing specifically for performance metrics
- Avoid High compression for important visual content
You can always test compression levels on a small set of images before applying them site wide.
Important notes
- Compression settings only apply to images optimized after the change
- Previously optimized images need to be restored and re optimized to apply a different level
- Keeping backups enabled is recommended when testing compression modes
This ensures you can balance image quality and performance based on your site needs.