Lossy vs Lossless Compression: What Is the Difference?
Learn the difference between lossy and lossless compression, how each method affects image quality and file size, and when to use each one.
Quick answer
Lossless compression reduces file size without removing image data, while lossy compression removes some information to achieve greater size reductions. Choose lossless compression when preserving exact data matters and lossy compression when a smaller file is more important.
What is lossless compression?
Lossless compression reduces the amount of space needed to store an image without permanently removing its original data. When the file is decoded, the original information can be reconstructed exactly.
This type of compression is useful when every detail needs to remain unchanged. PNG is a common example of an image format that uses lossless compression, making it suitable for graphics, screenshots, logos, and images containing sharp text.
What is lossy compression?
Lossy compression reduces file size by removing some image information. The compression process is designed to remove details that are generally less noticeable, allowing the image to become much smaller while still looking good in many situations.
JPG is a common example of a lossy image format. Increasing the compression level can reduce the file size further, but excessive compression may produce visible artifacts, blurry details, or changes around sharp edges.
Lossy vs lossless compression
The main difference between lossy and lossless compression is whether image information is permanently removed. Lossless compression keeps the original data intact, while lossy compression sacrifices some information to achieve greater file-size savings.
For everyday photos, lossy compression is often practical because photographs contain a large amount of visual information that can be reduced without an obvious difference at normal viewing sizes. For graphics and images where exact details matter, lossless compression may be more appropriate.
- • Lossy compression usually creates smaller files.
- • Lossless compression preserves the original image data.
- • Lossy compression can introduce visible quality loss at high compression levels.
- • Lossless compression is useful for graphics, screenshots, and images that need exact detail.
- • Always keep the original when you may need the highest-quality version later.
How to choose between lossy and lossless compression
Choose the compression method based on how you plan to use the image. If your main goal is a smaller file for a website, email, or everyday sharing, lossy compression can provide a useful reduction in size.
If the image contains text, precise graphics, or information that must remain unchanged, lossless compression can be a better fit. You can also keep the original and create a compressed copy for sharing or uploading.
- • Photos for websites and social sharing: lossy compression is often suitable.
- • Logos, icons, and graphics: lossless compression can preserve sharp details.
- • Screenshots containing text: use lossless or a high-quality setting.
- • Original or archival files: keep the untouched source file.
Which image formats use lossy or lossless compression?
Different image formats use different compression methods. JPG is commonly associated with lossy compression, while PNG uses lossless compression. WebP supports both lossy and lossless compression, giving you more flexibility depending on the type of image and the desired file size.
The format you choose should depend on the image itself and where it will be used. A photograph and a simple logo may benefit from different formats and compression settings.
What happens when you compress an image repeatedly?
Repeatedly applying lossy compression can gradually reduce image quality because additional image information may be discarded each time the file is saved. The effect can become more noticeable after several compression cycles.
For the best results, keep the original image and create your compressed version from that original whenever possible. This gives you a clean source if you need to create another version later.
Frequently asked questions
- What is the difference between lossy and lossless compression?
- Lossy compression removes some image data to create a smaller file, while lossless compression reduces file size without permanently removing the original data. Lossy compression usually provides greater size savings, while lossless compression preserves the original information.
- Is lossy or lossless compression better?
- Neither method is always better. Lossy compression is useful when smaller file sizes are important, such as for website images and everyday photo sharing. Lossless compression is more suitable when image details must be preserved exactly, such as for certain graphics, screenshots, and source files.
- Is JPG lossy or lossless?
- JPG, also known as JPEG, normally uses lossy compression. Saving a JPG with stronger compression can make the file smaller, but some image information is permanently discarded. PNG uses lossless compression, while WebP supports both lossy and lossless compression.
- Can lossy compression be reversed?
- No. Once lossy compression removes image information, converting the file back to another format cannot restore the discarded detail. Keep the original image if you may need the highest available quality later.