Frequently asked questions

No. SlimMyFile loads its compression code into your browser, and your files are read and processed on your device. File contents and filenames are never sent to us or to third parties.

No. Files are held only in your browser’s memory while the page is open. They are not written to persistent browser storage, and closing or reloading the page discards them.

Once a tool page and its compression engine have loaded, processing does not need a connection. The site is not a full offline app, so you need to be online to open pages.

PDF for document compression, and JPG/JPEG, PNG and WebP images. Images can be saved as JPEG, PNG or WebP.

Lossless compression keeps every pixel identical and rewrites the data more efficiently. Lossy compression removes some detail to produce much smaller files. JPEG, WebP and PNG colour reduction are lossy; PNG lossless optimisation is not.

This can happen when an image was already heavily compressed, when you choose a high quality, or when converting to a less efficient format. SlimMyFile always shows the real size and keeps your original when nothing else changed.

Re-encoded images do not keep EXIF metadata such as GPS location or camera details. PDF optimisation keeps document properties; High compression also removes the XMP metadata stream.

It depends on the content. PDFs with large photos or scans often shrink significantly; text-only PDFs usually do not. We never promise a specific reduction and we report the actual result.

Yes. Any modification invalidates a digital signature. SlimMyFile detects signed PDFs and asks you to confirm before processing them.

An optional mode that renders every page as a compressed image. It suits scanned documents but removes selectable text, links, form fields and accessibility information, so it requires your explicit confirmation.

The tools are designed for current versions of Chrome, Edge, Firefox and Safari on desktop and mobile. They need Web Workers and WebAssembly; if your browser lacks them, the tool shows a message instead of failing silently.

By default, up to 50 MB per image and 150 MB per PDF. The real limit is your device’s memory: phones may struggle with very large files that a desktop handles easily.

All the work happens on your device, so speed depends on its processor and memory. Large PDFs and high-resolution images take longer on mobile devices.