How to Compress Images | Free Online Image Size Reducer

Tried uploading an image to a website but hit the file size limit? Couldn't attach a photo to an email because it was too large? This guide shows you how to reduce image file sizes for free while keeping quality intact.

Why Images Get So Large

Here are the main reasons image files become oversized:

• High-resolution capture: Modern smartphones and cameras produce photos of 5MB–10MB or more per shot
• Uncompressed formats: PNG and BMP formats preserve quality but result in large file sizes
• Unnecessary metadata: EXIF data including date, GPS location, and camera settings adds bulk
• Oversized dimensions: Using a 4000px-wide image when 1200px would suffice for web display

For image-heavy web pages, compressing images alone can dramatically improve loading speed.

How to Compress Images with an Online Tool

The simplest approach is a browser-based online tool — no installation required and it works on mobile too.

With sakutto's image compressor, it takes just 3 steps:

Step 1: Add Your Image Files

Drag and drop images or click the file picker button. Supports JPEG, PNG, WebP, and HEIC formats, with batch processing for multiple files.

Step 2: Set Output Format and Quality

• Output format: Choose from JPEG, WebP, or PNG (or keep the original format)
• Quality: Adjust from 10% to 100% using the slider (80% is recommended as default)

Step 3: Compress and Download

Click "Start Compression" and the processing happens right in your browser. Once complete, download files individually or as a ZIP archive.

Compression Differences by Image Format

Each image format has different compression characteristics and ideal use cases:

Recommended Formats by Use Case

• Website images: WebP offers the best balance — lighter than JPEG with excellent quality
• Email attachments / social media: JPEG is the safe choice — opens on any device
• Logos, icons, images needing transparency: Use PNG

Tips for Compressing Without Losing Quality

Here's how to minimize quality loss when compressing images:

• Choose the right quality setting: JPEG quality of 70–85% produces results that are visually indistinguishable from the original
• Resize before compressing: Downsizing a 4000px image to 1200px drastically reduces file size on its own
• Compress only once: Re-compressing an already compressed image offers little benefit and just degrades quality
• Match format to content: Use JPEG or WebP for photos, PNG for illustrations

FAQ

Is image compression free?

Yes. sakutto's image compression tool is completely free — no registration, no usage limits. Just open your browser and start compressing.

How much quality is lost?

It depends on your settings. At 80% JPEG quality, the difference from the original is virtually undetectable. Below 70%, you may notice noise when zooming in, but it's perfectly fine for web display.

What's the difference between JPEG, PNG, and WebP?

JPEG is a lossy format ideal for photos — small file sizes but quality degrades with each save. PNG is lossless, perfect for illustrations and screenshots, but produces larger files for photos. WebP, developed by Google, handles both photos and illustrations and is about 30% smaller than JPEG.

Is my file uploaded to a server?

No. All processing happens in your browser. Your images are never sent over the internet, so it's safe to use with private photos.

Can I compress images on my phone?

Yes. It works in Safari on iPhone and Chrome on Android. No app needed — just select images from your browser and compress.

Summary

Image compression can dramatically reduce file sizes while barely affecting visual quality. With an online tool, there's nothing to install — just compress right from your browser. Whether you're optimizing website performance or reducing email attachment sizes, give it a try.