How FilesKit processes your files

• You choose a file. Your browser gives the page read access to that file only.
• The tool checks the file’s type by looking at its content, not just its name, and checks its size against the tool’s limits.
• The heavy work runs in a Web Worker, a background thread in your browser, so the page stays responsive.
• The result is created in your browser’s memory and saved through your browser’s normal download feature.

When you open the site, your browser downloads FilesKit’s own code from this website. Some tools download more code the first time you use them, for example the PDF engine or an image decoder. That is code coming to you; your files are not sent anywhere.

• pdf-lib reads and writes PDF files.
• PDF.js (by Mozilla) draws PDF pages for previews and for PDF-to-image conversion. Its decoders for JPEG 2000, JBIG2 and colour profiles are WebAssembly modules served from this website.
• Your browser’s own image engine decodes and encodes JPG, PNG and WebP images.
• fflate creates ZIP files when you download several results at once.

FilesKit has no server that receives, stores or processes your files, and the site contains no analytics, advertising or tracking scripts. Where the host supports custom headers, FilesKit sends a Content Security Policy that tells browsers to allow network requests only to the site’s own address.

Like any website, the hosting provider sees standard request information such as your IP address and the pages you request when your browser loads FilesKit.

• Your device does the work, so large files depend on your browser’s memory. Phones and tablets have the lowest limits.
• Some results cannot match desktop software, for example very heavy PDF compression.
• A tool needs a current browser. Older browsers may lack features such as image processing in workers.