KissPDF

Technical transparency

How local PDF processing works

The selected document is read by browser code on your device. KissPDF does not send the PDF bytes to a remote document-processing API. The exact local engine depends on the operation.

The processing path

  1. You choose a local file through the browser file picker or drag-and-drop interface.
  2. The browser grants the page access to that selected file; KissPDF reads it into memory.
  3. A local PDF engine performs the requested operation.
  4. The result is converted to a temporary browser Blob and downloaded as a new file.
  5. Temporary object URLs and in-memory resources are released when the task or page ends.

“Local processing” describes where the PDF operation happens. The website can still make ordinary requests for application assets, analytics, or the WebAssembly compression engine; those requests do not contain the selected PDF file.

Browser technologies used by KissPDF

PDF.js

Reads PDF structure, renders thumbnails and pages, and supplies page data for image conversion and preview workflows.

Browser-side PDF processing

Creates, copies, merges, extracts, rotates, protects, and writes documents directly in browser memory.

WebAssembly compression

Powers Compress PDF inside a dedicated Web Worker. The browser build is version-pinned and size-optimized.

Browser Canvas

Creates JPG and PNG page images and performs pixel-level color inversion. Raster workflows do not retain searchable text.

What local processing cannot guarantee

PDF is a complex format. Creating a new document can change signatures, forms, bookmarks, attachments, scripts, layers, color handling, accessibility information, and unusual object structures. A tool page states when it copies pages, renders pixels, applies encryption, or rewrites the complete file.

  • Keep the original document until the result has been checked.
  • Do not process a signed master copy when signature validity matters.
  • Review forms and interactive documents in the intended PDF reader.
  • Large or image-heavy files may exceed the memory available to a mobile browser.