📦 Image Compression

Compresses the file size of images. Output in JPEG, PNG, and WebP formats with quality adjustment.

📦 Drag & drop images

or click to select (JPEG / PNG / WebP)

Usage and Application Examples
  • Lightweight eye-catching images for blog posts to improve page display speed
  • Optimize image size before posting to social networking sites to save traffic
  • Keep email-attached images within capacity limits
  • Optimize images to improve your website's Lighthouse score

What is Image Compressor?

Image Compressor is a free browser tool that reduces file sizes for JPEG, PNG, and WebP images without compromising visual quality noticeably. Instead of uploading files to cloud services, compression happens directly on your device—your images never leave your computer. The tool includes a quality slider so you can choose how much compression to apply, and shows you a before-and-after preview. For example, a 5MB photograph can often be compressed to under 1MB with only minimal quality loss visible to human eyes.

How to Use

Upload an image by dragging it onto the page or clicking to browse files. The tool displays the original file size and shows a preview of your image. Adjust the quality slider from 0 to 100 to control compression strength—higher values preserve more detail but result in larger files, while lower values create smaller files but with more visible quality loss. Select your desired output format: JPEG for photographs and colorful images, PNG for images needing transparency or sharp text, or WebP for maximum compression on modern browsers. Preview the result in real-time to see the quality-to-size tradeoff. When satisfied, click download to save the compressed image to your device.

Use Cases

Blog writers posting 10+ images per article optimize each image to improve page load speed, aiming to keep all images under 200KB combined. Studies show that every 1-second delay in page load time reduces user engagement by approximately 10%, making compression essential for keeping readers on your site. Social media managers uploading hundreds of photos to Facebook or Instagram monthly compress each image to stay within data allowances, potentially saving gigabytes monthly. Email users attaching images to messages often encounter size limits—Gmail caps attachments at 25MB, so compressing a high-resolution photo from 8MB to 2MB ensures reliable delivery. E-commerce product photographers reduce catalog image file sizes from 50MB to 500KB each, enabling websites to load product galleries 10 times faster. Content creators preparing images for newsletters compress graphics to ensure they download quickly even on slow connections.

Common Mistakes & Solutions

The biggest mistake is over-compressing images to tiny sizes, resulting in visible pixelation or blurriness that damages professionalism. Solution: use the preview to check quality before downloading—aim for a balance where file size drops by 50-70% while quality remains acceptable. Another common error involves choosing the wrong format; PNG is necessary for graphics with transparency, but using PNG for photographs wastes space since JPEG compresses photos more efficiently. Solution: use JPEG for photos and illustrations, PNG only when transparency is needed, and WebP for modern websites supporting it. Many users check only the file size without comparing the actual visual quality. Solution: always look at the side-by-side preview, especially for text and detailed graphics where compression artifacts become more noticeable.

Tips & Insights

Understanding format differences helps you choose compression wisely. JPEG works best for photographs and images with many colors, achieving 5:1 compression ratios easily. PNG preserves quality for graphics and images with transparency but compresses less effectively—typically 2:1 ratios. WebP format, supported by Chrome, Firefox, and Edge, often compresses 25-35% better than JPEG while maintaining quality. The quality slider's sweet spot usually sits around 75-85 for most purposes—pushing quality to 95+ yields marginal visual improvements but doubles file sizes. For websites, Google recommends serving images under 100KB each for thumbnail galleries and under 200KB for featured images. When compressing multiple images, check the file size reduction percentage rather than absolute sizes, as different images compress at different rates depending on content complexity.

Frequently Asked Questions

How are images compressed?

Compresses within the browser using the Canvas API. You can adjust the compression ratio with the quality slider and see the change in file size.

Will image data be sent to the server?

No. All images are processed within the browser. All processing is done within the browser and no image data is sent to any external source.

Which has a higher compression ratio, WebP or JPEG?

In general, WebP can achieve the same image quality at 25-35% smaller file size than JPEG. However, older browsers may not support WebP.

What is the maximum size of images that can be compressed?

Images up to about 10 MB can usually be compressed without problems because they are processed in the browser's memory. Very large images may not be processed due to browser limitations.

品質スライダーはどの程度の値を選ぶべきですか?

75~85%の品質設定が、視覚的な劣化を抑えながら高い圧縮率を実現するバランスが取れています。Webサイト用途なら80%、印刷用なら90%以上、SNS共有なら70%程度をお勧めします。

複数の画像を一度に圧縮できますか?

現在のバージョンは1つの画像ずつ処理する仕様です。複数の画像を順番に圧縮する場合は、各画像ごとにツールを使用すれば効率的に処理できます。

圧縮後の画像をオリジナルの品質に戻すことはできますか?

いいえ、圧縮は不可逆的なプロセスのため、一度圧縮した画像をオリジナルの品質に戻すことはできません。重要な画像は圧縮前に元のファイルを保存しておくことをお勧めします。

目標ファイルサイズ機能はどのように機能しますか?

目標ファイルサイズを入力すると、ツールが自動的に最適な品質と解像度を計算して圧縮します。指定サイズに近い結果を目指しますが、完全に一致するとは限りません。

PNG画像を圧縮するとき、透明度は保持されますか?

はい、PNG形式での圧縮時は透明度(アルファチャンネル)が保持されます。ただし色情報の圧縮により、わずかな色変化が生じる可能性があります。

WebPで圧縮すると、古いブラウザでも表示できますか?

いいえ、WebP形式は古いブラウザ(Internet Explorer、古いSafariなど)では表示できません。汎用性が必要な場合はJPEG形式、透明度が必要な場合はPNG形式をお勧めします。