Image Compressor

What is image compression?

Image compression reduces the file size of a digital image by discarding data that the human eye is unlikely to notice. There are two types: lossy and lossless. Lossy compression (used by JPEG and WebP) permanently removes some image data to achieve smaller sizes — the amount removed is controlled by a quality setting. Lossless compression (used by PNG and GIF) reorganises the data without discarding any, which produces smaller files than the original encoding but not as small as lossy. For photographs, lossy compression at 75–85% quality is typically indistinguishable from the original at normal viewing distances.

The practical consequence: a 5 MB JPEG photo at 80% quality typically becomes 1–2 MB with no visible degradation. That same photo as WebP at 80% might be 700 KB. Neither change is perceptible on a standard display. This matters for email attachments, social media uploads, and web page load times.

How does browser-based compression work?

OffCloud.tools uses the browser-image-compression library, which runs inside a Web Worker — a background thread in your browser. Your image is decoded into raw pixel data using the browser's built-in Canvas API, then re-encoded at the target quality or file size. Because everything happens inside the browser tab, your files never leave your device.

You can verify this yourself: open your browser's Developer Tools (F12), click the Network tab, and compress an image. You will see zero upload requests. The only network activity is loading the page and its static assets.

How to compress images with OffCloud.tools

1. Drop one or more images onto the drop zone, or click Choose files.
2. Set your target quality (80% is a good starting point for photographs).
3. Choose an output format — keep Original, or switch to WebP for smaller files.
4. Optionally set a maximum target file size. The tool will adjust quality automatically to meet it.
5. Watch the per-file progress bars. Compression runs in the background.
6. Review the before/after sizes shown for each file.
7. Download individual files or click Download all as ZIP.

Is it safe to compress images online?

With most online image compressors, your files are uploaded to a remote server for processing — meaning passport photos, sensitive documents, and personal images pass through infrastructure you know nothing about. OffCloud.tools is different: compression runs entirely inside your browser using the Canvas API built into every modern browser. Your files are never transmitted anywhere.

This makes it safe to compress confidential images, medical scans, legal documents, or anything else you would not normally upload to an unknown service. The privacy guarantee is structural — not a policy promise. The code physically cannot transmit your files because it runs in a sandboxed browser context with no server endpoints.