These guides cover the technical side of browser-based PDF merging, step-by-step instructions for different use cases, and answers to the questions we get asked most. All guides are written by the mergepdf.dev team and kept up to date.
How to Merge PDF Without Uploading
Step-by-step guide to combining PDFs privately in your browser. Covers desktop, iPhone, Android, and offline use.
How Browser-Based PDF Merging Works
Technical explanation of the File API, pdf-lib, and why files never leave your device. Includes a DevTools verification walkthrough.
What these guides cover
How to Merge PDF Without Uploading is the practical guide. It walks you through the four steps to merge PDFs in your browser, explains how to verify nothing is being uploaded, covers mobile (iPhone and Android), and answers the most common questions. If you just want to get something done, start there.
How Browser-Based PDF Merging Works is the technical guide. It explains what actually happens when you merge PDFs — the File API reads files into memory, pdf-lib processes them locally, and a Blob download delivers the result. It also explains why local processing is safer than upload-based tools, and how to verify it yourself using browser DevTools. If you're security-conscious or just curious, that's the one to read.
Related tools
These guides support the tools on this site. Depending on your situation, one of these pages might be exactly what you need:
- Merge PDF without upload — privacy-focused, zero server contact
- Merge PDF offline — for flights, travel, and remote work
- Merge PDF locally — GDPR-safe, for sensitive documents
- Merge PDF offline — for flights, travel, and remote work (also covers no-internet scenarios)
- Merge PDF on Mac — no Preview, no Adobe needed
- Merge PDF on Windows — no software installation
- Merge PDF on iPhone — Safari and iCloud ready
- Merge PDF on Android — Chrome and Google Drive ready
- Merge large PDF files — no size limits
- Combine scanned PDF — preserves scan quality
- Merge multiple PDF files — batch merge 10, 20, 50+ files
About these guides
Written by the mergepdf.dev team. We built this tool because we needed a PDF merger that didn't upload files to a server — and we couldn't find one that was both private and easy to use. These guides explain the decisions we made and how the technology works.
All guides are kept up to date. If something is wrong or unclear, let us know.