Image Compressor

Our compression tool supports all mainstream formats including JPG/JPEG, PNG, GIF, WebP, and BMP. Format conversion is also possible during compression.

This is normal! Reasons: ①Your original image may already be highly compressed (e.g., saved at 60% quality). When you choose 80% quality for re-compression, Canvas re-encodes with higher quality, making the file larger. ②It's like rewriting an already compressed article in more detail. ③Suggestion: For optimized images, try lower quality (30-50%) or convert to WebP format.

The 100% quality parameter doesn't mean 'keep original size' but 'recompress using highest quality JPEG encoder'. Your original file may have been compressed and optimized by professional software at lower quality (like 60%), while Canvas uses standard compressor for re-encoding, so even 100% quality might be larger than the original file.

Bytes/pixel ratio = file size ÷ image pixels. Reference standards: <0.2 is highly compressed, 0.2-0.5 is moderately compressed, 0.5-1.0 is lightly compressed, >1.0 is low compression or uncompressed. If your image has a low bytes/pixel ratio, it's already highly optimized and re-compression may be ineffective.

Smart compression algorithms can dramatically reduce file size while maintaining excellent visual quality. You can precisely control the balance between quality and file size through the quality slider.

Lossless compression maintains 100% original quality but has relatively lower compression ratios. Lossy compression achieves higher compression ratios through slight quality loss, usually imperceptible visually.

JPG is suitable for photos and complex images, PNG for transparent backgrounds and simple graphics, WebP provides the best compression but slightly less compatibility. Choose the most suitable format based on your use case.

Negative numbers indicate file size increase. For example, -159% means file size increased by 159%. This usually happens when: ①Original image is already highly optimized ②Too high quality settings chosen ③Canvas re-encoding loses original optimization algorithm effects. Solution: Lower quality settings or try format conversion.

Completely safe! All compression processing is done locally in your browser, images are not uploaded to our servers, ensuring complete privacy protection and data security.

Already highly compressed images (like processed JPGs) have limited re-compression benefits. PNG and original photos usually have better compression results. Try format conversion for better compression ratios.

Currently the tool processes one image at a time to ensure optimal performance and quality. For batch needs, you can quickly process multiple images consecutively.

①Check system-provided 'compression diagnostics' tips ②For web use, recommend quality settings 70-85% ③For print use 90-95% ④For storage savings try 30-50% ⑤For optimized images recommend WebP format conversion ⑥Always check before/after effect comparison.