無料オンライン画像リサイズ

The resizer accepts all common browser-supported image formats: JPEG, PNG, WebP, GIF (first frame only), and BMP. The output is always a PNG or the same format as the original, depending on the browser's canvas export settings.

Resizing to smaller dimensions reduces file size proportionally — a 2000px image resized to 1000px uses roughly one-quarter the pixels, significantly shrinking the file. However, upscaling (making the image larger) increases file size and reduces quality by stretching existing pixels.

The tool allows output dimensions up to 8,000 × 8,000 pixels. In practice, very large outputs may be slow or cause memory warnings in older browsers. For web use, keeping images under 2,000px wide is sufficient for most displays.

Aspect ratio lock keeps the original width-to-height ratio when you change one dimension. To crop to a different ratio (e.g. 16:9 from a 4:3 photo), uncheck the lock and set both dimensions independently. The image will stretch — use a dedicated crop tool for non-distorted cropping.

No. All resizing happens entirely in your browser using the Canvas API. Your image is never transmitted to a server, and nothing is stored after you close the tab.

Yes, the 画像リサイズ on Allio Tools is completely free with no sign-up or registration required. It works directly in your browser.

数秒でカスタムサイズに画像をリサイズします。 No data is sent to a server — everything runs locally in your browser for maximum privacy and speed.

No installation needed. The 画像リサイズ runs entirely in your web browser on any device — desktop, tablet, or mobile.

Completely safe. The 画像リサイズ processes everything locally in your browser. No input data, results, or usage information is ever transmitted to or stored on any server.

After the page loads for the first time, the 画像リサイズ works without an internet connection for all client-side processing. Tools that fetch live external data (such as DNS or network lookups) require an active connection.

The 画像リサイズ works with common image formats supported by your browser, including JPEG, PNG, WebP, and GIF. SVG support varies by tool. No format conversion plugin or driver is needed.

Yes. The 画像リサイズ processes files entirely in your browser using the Canvas API. Very large files (over 20 MB) may take a few extra seconds on older or lower-powered devices. Closing other tabs can free up memory for better performance.

Yes. The 画像リサイズ is built with standard browser APIs and works on all modern browsers including Chrome, Firefox, Safari, and Edge — on both desktop and mobile. No plugins, extensions, or third-party software are required.

Select and copy the result text to paste into any document or app. For image tools, a Download button saves the file directly to your device. Your browser's built-in screenshot function also captures results quickly. No account or login is required.