Secure PDF Comparison — Your Files Never Leave Your Browser

Most PDF comparison tools process your documents on their servers. DrawDiff is architected differently: the entire comparison engine runs in JavaScript inside your browser tab. Your files are never transmitted, never stored, never seen by anyone but you.

How Local Processing Works

When you load a PDF into DrawDiff, your browser reads it from your disk using the standard File API — the same mechanism used when you preview a file locally. The file data goes into browser memory. DrawDiff's JavaScript comparison engine then processes it entirely within that memory.

There are no API calls, no background uploads, no telemetry that includes your document content. The only network requests DrawDiff makes are to load the application itself (the HTML, JavaScript, and fonts from our CDN) — and those happen before you load any PDF.

Compare PDFs Without Uploading — Who This Is For

Any situation where uploading a document to a third-party cloud service is restricted, prohibited, or simply inadvisable. Common examples:

• Defense and aerospace contractors — drawings subject to ITAR or EAR export control regulations
• Legal professionals — comparing contract versions containing privileged or confidential information
• Healthcare — comparing documents that may contain protected health information
• Financial services — comparing regulated documents under strict data handling requirements
• Corporate engineering — proprietary designs and trade secrets that cannot be shared with external services
• Government contractors — technical data packages and CDRLs with distribution restrictions

DrawDiff vs Cloud-Based Comparison Tools

What DrawDiff Does Collect

DrawDiff uses Google Analytics 4 to collect anonymous, aggregate usage statistics — which pages are visited, which features are used (compare run, alignment tool opened, etc.), and approximate geographic region. This data is never linked to your document content or filenames. It is used solely to understand how the tool is being used and to prioritise new features.

Google Analytics can be blocked by browser extensions (uBlock Origin, etc.) or by enterprise network policies. DrawDiff functions fully regardless of whether analytics are blocked. See the Privacy Policy for complete details.

Offline and Air-Gapped Use

Once the DrawDiff page has loaded in your browser, it can be used entirely offline. The application — all JavaScript, the PDF.js rendering engine, fonts — is cached by the browser. On a subsequent visit without network access, the cached version loads and runs normally.

For fully air-gapped environments where even the initial page load cannot reach the internet, DrawDiff can be hosted on an internal web server. The application is a single self-contained HTML file with no server-side components. Contact us if you need guidance on internal deployment.