Client-Side PDF Processing: Where Your Files Go
Client-side PDF processing means the work happens inside your browser tab: the document is read, changed and saved on your own device, and it does not travel over the network. Server-side processing sends the file to a remote computer, which does the work and returns the result.
ProPDF uses both. This guide lists which tools work in which way, what happens to a file sent to the server, what the site itself records, and how to inspect requests and browser storage with your browser's developer tools.
How processing in the browser works
When you open a browser tool, the site sends your browser the code it needs, including open-source libraries such as pdf-lib, pdf.js and JSZip. Your file is then read into the memory of the tab, processed there and handed back to you as a download.
Most PDF results also stay in the page's memory, so the panel that appears after the download can pass the result to another tool without selecting it again. Reloading or closing the page clears it.
Browser tools have no file size cap: only your device's memory matters. There is no upload to wait for either, since the file is not sent anywhere.
The 13 tools that run in your browser
13 of the 21 tools process your file on your device and do not send it anywhere:
- Combining and splitting: Merge PDF, Split PDF and Extract Pages.
- Page layout: Organize, Rotate PDF and Delete Pages.
- Images: PDF to JPG, PDF to PNG and JPG to PDF.
- Marks on the page: Watermark, Page Numbers and Sign PDF.
- Review: Compare, which shows two documents side by side.
The 8 tools that use a server
The other 8 tools send your file over HTTPS to the ProPDF server on AWS in the Paris region (eu-west-3): Compress PDF, PDF to Word, Word to PDF, Edit PDF, Redact, Protect, Unlock and Chat with PDF. Word to PDF, for example, relies on LibreOffice running on the server, and the chat relies on Amazon Bedrock. These tools accept files up to 4 MB, and here is what happens to your file:
- It is processed on the server, then deleted as soon as the task ends. No copy is kept.
- Some tools, such as Word to PDF, Protect and Unlock, go through a temporary file on the server while they work, and that file is deleted as soon as the task ends too.
- Chat with PDF keeps the text of your document and the conversation in your tab, which sends them with each question so that follow-up questions work; the server keeps neither once it has answered. The text and your questions are sent to Claude models from Anthropic through Amazon Bedrock, with a European inference profile.
- Edit PDF sends a PDF of up to 4 MB in full when you open it and again after each change, because text detection and rewriting happen on the server; a larger PDF is not sent, and only signatures can be added to it.
What the site itself records
The server keeps no copy of your files or their content, and that includes the chat. With your consent, audience-measurement cookies (Google Analytics) are set, and you can change your choice at any time with the Manage cookies button in the site footer. There are no ads.
When you download a result, the page sends a download event to Google Analytics: the tool name, the file extension and the file size, never the file name or the content.
The site's typefaces load from Google Fonts, so your browser also contacts Google's font servers. In your browser's local storage, the site's own code saves at most three settings: the theme, the language and your cookie choice.
How to check it yourself
Your browser's developer tools list every request a page makes. They cannot show what happens on the server, but four checks cover the browser side:
- Open the developer tools, often with the F12 key or from the browser menu, and select the Network tab.
- Merge two files with Merge PDF. You see requests for the site's own files, its fonts and analytics, but none that carries your documents. Entries that start with data: or blob: are copies inside the page, not uploads.
- Now compress a file with Compress PDF. A POST request goes to an address that contains eu-west-3, with your file, encoded as text, in its body, and the compressed file comes back in the response.
- Open the Application tab (Storage in Firefox), then Local Storage for the site. The site saves only small settings there, such as the theme, the language and your cookie choice, never a document.
Choosing a tool for a sensitive document
If you want a document to stay on your device, use a browser tool when one does the job: sign with Sign PDF rather than with the signature mode of Edit PDF, for example.
When a task needs a server tool, send only what is needed. Remove the pages that are not concerned with Delete Pages, or keep the ones you need with Extract Pages, both in your browser, then process the shorter file. One limit: what the pages you keep share with the others can stay in the file, out of sight, such as the other half of a two-page spread.
Whichever tool you use, your files are not kept: browser tools do not send them anywhere, server tools delete them as soon as the task ends, and the chat keeps the document text and the conversation in your tab rather than on the server.