How local PDF processing works

FlowPDF is a browser application. Instead of sending your document to a remote conversion service, it uses JavaScript PDF and canvas libraries to read and transform files inside the browser tab.

1. You choose a local file

The browser grants the page temporary access only to the file you select. FlowPDF does not scan unrelated folders and cannot silently browse files on your device.

2. The browser reads the document

PDF.js renders previews and extracts supported text. PDF-lib and other browser libraries create or modify PDF structures. Image and canvas tools handle operations that require page rendering.

3. The requested operation runs locally

Simple operations such as merging, splitting, reordering and copying pages preserve PDF page structures. Image-based compression and Redact PDF rebuild every output page as an image. Selectable text, links and interactive fields are not retained in those results.

4. Your browser creates the download

The result is assembled in memory and exposed as a local download. Your original file remains unchanged unless you later replace it yourself.

Important limitations

• Very large documents may exceed the memory available to a phone or older computer.
• Closing or refreshing the tab clears active work that has not been downloaded.
• Some protected, malformed or uncommon PDF features may not be supported.
• Local processing reduces document-upload exposure but does not replace organizational security controls.

Analytics are separate from documents

FlowPDF measures general site and tool usage to improve the experience. Tracking events are designed without file names, passwords, document text or signature images. See the Privacy page for details.

Local processing still uses a website

Opening FlowPDF downloads the application, images and supporting browser libraries. Some resources come from third-party delivery networks; the PDF security engine is bundled with the site. These ordinary resource requests are separate from document processing. Local processing does not mean the whole website is offline or that visiting it sends no network information.

Move between tools deliberately

Some PDF tools can reuse the document selected in the current session, saving another attachment step. A downloaded result is a separate file: attach that result if the next operation should use your changes rather than the original. Save important outputs before refreshing or closing the tab.