I analyzed what happens when you upload a photo to 5 popular free image compression sites.
The Test
I uploaded a 4.2MB photo to each service and monitored network requests. Results:
- Service A: File sent to their CDN (AWS us-east-1). 12 analytics trackers fired simultaneously.
- Service B: File uploaded, but 5 minutes later a second request sent the file to a different domain.
- Service C: Cleanest of the five, but their privacy policy reserves the right to "use uploaded content to improve compression algorithms."
- Service D: 23 third-party scripts loaded on the page. Your image URL is accessible to all of them.
- Service E: Actually clean — only one request to their server for processing.
Only one of five didn't leak data to third parties. One.
The Alternative
I built compress2png.com to test whether image compression could work without any server. Turns out Canvas API + clever JavaScript handles it:
- Resize images client-side before export
- Strip EXIF/metadata in the browser
- Convert to optimal formats based on content
For format-specific needs, svg2png.org handles vector conversion and webp2png.io handles next-gen format conversion — all browser-local.
Check the Network tab next time you use a "free" online tool. You might be surprised what you find.
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