Love seeing more privacy-first tools in this space. One thing I've learned building PrivaVault (encrypted doc management, launching this weekend) is that users often underestimate how much metadata leaks even when the content is processed locally. For PDF tools specifically, creation timestamps, software versions, and author info can persist through merges unless explicitly stripped. Would be curious if merge-pdf.app handles metadata sanitization – it's one of those edge cases that matters a lot for privacy-conscious users but isn't always obvious at first glance.
Nice exercise, and as a local solution obviously better than all this "give your data and trust me" stuff. But why must everything nowadays be a browser-based tool? I'm still happy with tools like pdfunite from https://poppler.freedesktop.org/
totally understand. I think distribution on the Web is a lot easier than building desktop applications for Linux/Mac/Windows.
Also, sometimes I need to merge pdfs when I'm on my Android device, which would be another target to build an application for. Web makes it easy for me across a huge variety of devices
In Android I usw Termux which is a more or less Debian installation. But I understand that it's some kind of "generation conflict" where younger developers are more web centric than oldtimers, who know about the command line among other things ;-0
I used to use the other free online services, which send my files to their servers in order to perform the processing.
I moved to using a docker container when I became concerned about privacy (I merge a lot of invoices and financial documents)
So I built my own, free, privacy centric version