画像圧縮 - 無料オンライン | 可逆・非可逆圧縮

画像を無料でオンライン圧縮。可逆・非可逆圧縮。ウェブサイトの高速読み込みのための画像圧縮方法。

Drop your image here or click to select

or click to browse • Max 50MB

100% private • No uploads

Why Compress Images?

Large images slow down websites, consume storage, and fail email size limits. Compression reduces file size while preserving acceptable quality. Lossless compression keeps every pixel; lossy compression trades some detail for smaller files. Our compressor supports both modes and can target a specific file size.

Lossless vs Lossy Compression

Lossless (PNG): No quality loss. Best for graphics, logos, screenshots. Lossy (JPEG): Smaller files, minimal visible loss. Best for photos. Use our target size feature to hit exact KB goals.

How to Compress Images Online

Drag your image, choose mode (lossy or lossless), set quality or target size, and compress. For lossy: optionally set target KB—we recursively adjust quality until the target is met. Max dimension limits resize large images before compression.

Target File Size Feature

Enter desired size in KB (e.g., 200). Our algorithm adjusts JPEG quality in a binary search until output is within 1KB of target. Ideal for web specs or email limits.

Best Compression Settings

Photos: Lossy, 80-90% quality. Graphics: Lossless. Web: 70-85% or use target size. Thumbnails: 50-70% or max dimension 800px.

When to Use Max Dimension

Resize before compress for huge images. 2048px max is good for web. 4096px for high-res. Reduces both dimensions and file size.

Image Compression for Web Performance

Faster page loads improve SEO and user experience. Compress hero images, product photos, and gallery thumbnails. Use our tool to batch-optimize before upload.

Recommended Workflow

1) Resize if needed. 2) Choose lossy for photos. 3) Set target size or quality. 4) Download and replace originals. Test visually before deploying.

よくある質問

Is image compression free?
Yes. Free, unlimited. Client-side processing.
What is target file size?
Enter KB (e.g., 200). We adjust quality until output meets that size. Lossy only.
Lossless vs lossy?
Lossless keeps every pixel (PNG). Lossy reduces size more (JPEG) with minimal visible loss.
Are images uploaded?
No. Compression happens in your browser.
Max file size?
50MB per image.