Image Compression Guide
Use the compression ratio calculator, then learn how lossy and lossless methods affect quality, formats, and web performance.
Measure image compression
Compare before and after file sizes to quantify savings and choose an appropriate workflow.
Make image compression measurable
Calculate actual savings
Compare original and compressed file sizes as a percentage and ratio.
Understand the method
Choose lossy or lossless compression based on content and reuse needs.
Check visual quality
Use the result as a guide, then inspect fine details at intended display size.
Lossy vs lossless compression
| Method | What changes | Bedst til | Typical formats |
|---|---|---|---|
| Lossy | Discards selected image detail | Photos and web delivery | JPG, WebP, AVIF |
| Lossless | Preserves decoded pixels | Graphics, text, editing | PNG, lossless WebP |
Hvordan det virker
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1
Enter your requirements
Provide file sizes or choose the website image characteristics.
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2
Review the result
Read the calculated savings or recommended format and rationale.
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3
Download the decision
Save the result for a content or optimization workflow.
A practical image compression workflow
Resize oversized pixel dimensions before lowering quality. For photographs, test WebP, AVIF, or controlled JPG quality. For screenshots and graphics with sharp text, start with PNG or lossless WebP. Keep an original master and compress delivery copies.
Ofte stillede spørgsmål
What is image compression?
Image compression reduces storage and transfer size by encoding pixels more efficiently or discarding selected detail.
What is the difference between lossy and lossless?
Lossy compression removes some detail for smaller files; lossless compression preserves decoded image data.
What compression ratio is good?
There is no universal ratio. The right result is the smallest file that still looks acceptable at its intended size.
Image Compression Guide last reviewed: Jul 18, 2026.