Free Online Image Compressor — Compress Images in Your Browser

Features You Won't Find in Other Compressors

Draggable Before/After Comparison

Most compressors show you the compressed result separately — you have to switch tabs or scroll to compare. Our tool puts original and compressed images side by side with a draggable vertical divider. Slide the green line left or right to instantly see the difference. This visual comparison lets you find the sweet spot between file size and quality in seconds. Click anywhere on the comparison area to jump the divider, or drag it smoothly with your mouse or finger.

Auto-Compress to Target Size

Don't want to guess the right quality setting? Type your target file size — like "200" KB — and click "Auto". Our tool uses binary search across 14 quality iterations to find the exact compression level that fits within your target. The result is guaranteed not to exceed your specified size. Each iteration shows the quality level and estimated output size in real time, so you can watch the algorithm converge on the optimal setting.

Batch Compression with Individual Preview

Select multiple images at once. Each appears as a thumbnail card with file name, size, and dimensions. Click any card to switch the comparison view to that image. Download individual compressed files or download all at once. Sort your images by file size before compressing — put the largest files first to prioritize optimization.

Format-Aware Compression

Choose to keep the original format, or convert to JPG, WebP, or PNG during compression. WebP typically offers 25-35% better compression than JPG at the same quality level. For photos, JPG quality 70-80% usually provides the best balance. For graphics with text or sharp edges, PNG may be more appropriate despite larger file sizes. Our tool lets you compare multiple format options instantly.

How the Auto-Compress Algorithm Works

When you enter a target file size and click "Auto", the tool performs a binary search across the quality range (1% to 100%). At each step, it renders the image at the midpoint quality, measures the output size, and adjusts the search range — going lower if the result is too large, higher if there's room for more quality. After 12-14 iterations (typically under 2 seconds), it finds the highest quality that stays within your size limit. The bisection algorithm guarantees convergence, and the "no-exceed" rule means you'll never download a file larger than your target.

Privacy and Speed

Every compression operation runs in your browser using the Canvas API. Images are never uploaded. Disconnect your internet after the page loads — everything still works. This also means near-instant processing: no waiting for upload/download. A 10MB image compresses in under a second on a modern device.

Frequently Asked Questions

Which formats are supported?
Input: PNG, JPG, WebP. Output: PNG, JPG, WebP. You can convert between formats during compression.

Will I lose image quality?
It depends on your quality setting. Use the before/after comparison divider to visually verify acceptable quality before downloading.

What's the maximum file size?
No hard limit. Very large images (50MB+) may take a few seconds but are handled fine on most devices.

Can I compress on my phone?
Yes — the draggable divider works with touch, and the interface adapts to narrow screens.