Image Compressor

How to Use the Image Compressor

This free online image compressor reduces file sizes directly in your browser using the HTML5 Canvas API. Select an image file, adjust the quality slider to balance file size and visual quality, and the tool compresses your image instantly. You can then download the compressed version as a JPEG file. Since all processing happens client-side, your images are never uploaded to any server, ensuring complete privacy and fast results regardless of your internet connection speed.

Why Compress Images?

Image compression is essential for website performance, reducing storage costs, and faster file sharing. Large images slow down web pages, increase bounce rates, and hurt SEO rankings. Google recommends keeping page load times under three seconds, and images are typically the largest assets on a web page. Compressing images before uploading them to your website can dramatically improve page speed, user experience, and search engine performance. Email attachments also benefit from smaller file sizes.

How It Works

This tool uses the browser Canvas API to decode the image, render it to an off-screen canvas, and re-encode it as a JPEG at the specified quality level. JPEG compression is lossy, meaning some visual information is discarded to achieve smaller file sizes. At higher quality settings (80-95%), the visual difference is typically imperceptible to the human eye while still achieving significant size reduction. Lower quality settings produce smaller files but may show compression artifacts like blurring or banding.

Tips for Best Results

Start with the quality slider around 70-80% for a good balance between quality and size. Photographs typically compress well to 60-80% quality. Graphics with sharp edges or text may benefit from higher quality settings. For web use, aim for images under 200KB. If you need to preserve transparency, note that this tool outputs JPEG format which does not support transparency. For transparent images, consider using PNG or WebP format instead.

Image Compressorの使い方

このツールはブラウザ上で動作する無料の画像圧縮ツールです。HTML5 Canvas APIを使用して画像を読み込み、品質スライダーで圧縮率を調整し、JPEG形式でダウンロードできます。すべての処理はクライアントサイドで行われるため、画像がサーバーにアップロードされることはなく、プライバシーが完全に保護されます。