Guide
Using HerePDF With No Internet: Proof That Your Files Stay on Your Device
By Happy Turtle Tech · Published · Updated
Part of the topic PDF Privacy: What Leaves Your Device and What the File Reveals
Most PDF sites say your files are safe. Few let you check. There is a simple test that needs no technical knowledge: use the tool with the internet switched off. A tool that still works cannot be sending your document anywhere while it does.
Why this is a fair test
Upload-based PDF tools send your file to a server, do the work there, and send the result back. Without a connection they simply stop. HerePDF does the work inside your browser, so the only thing it ever needs from the network is the site itself. Once the site is stored on your device, the network is not needed at all, with one exception: OCR PDF, whose engine and language files are not part of that copy (see below).
What gets stored
The first time you open HerePDF, your browser quietly keeps a copy of the site's own pages and code in the background, about 3 MB in total. That includes the PDF reader code the tools use. When it has finished, the footer of every page says "Works offline: ready". If you leave the page before it finishes, nothing breaks; it starts again on your next visit.
The OCR PDF tool is the exception. Its engine and language files (about 2 to 5 MB for the engine and one language, 21 MB for all seven) are not in that stored copy. They are saved the first time you use OCR on a page the offline copy already controls, which means a later visit rather than the visit that first stored the site. So use OCR once while online on a later visit; after that, that language works with the network off. Your browser may clear the files, and a language you have not used yet is not there.
Your documents are never part of what is stored. The files you open are read into memory, worked on, and gone when you close the page.
Try it yourself
- Open the merge tool with a normal connection and wait for "Works offline: ready" in the footer.
- Switch on airplane mode, or turn off Wi-Fi and mobile data.
- Reload the page. It still opens.
- Add two PDFs and merge them. The result downloads as usual.
You can open other tools and the guides the same way. If you would rather see the evidence than take the footer's word, open your browser's developer tools, choose the Network tab, and run the merge: you will see no request carrying your file. The guide on merging PDFs in the right order is a good companion for the next time you need to combine documents.
Installing it
Some browsers offer to install HerePDF, giving it an icon on your home screen or desktop and a window of its own. It is the same site and works the same way; it is just easier to open. Look for an install option in the browser's menu or address bar. Nothing is lost if you skip it.
Limits worth knowing
- Browsers can clear stored files. Some phones do it after about a week of not using a site. The footer follows what is actually stored, and the next visit stores it again.
- Ads, visitor statistics and links to other sites need a connection, so they do nothing offline. That does not affect the tools.
- The stored copy belongs to one browser on one device. A different browser or a new phone needs its own first visit.
- If you have a data-saving mode switched on, or a very slow connection, the copy is not downloaded.
- When you are online and a new version of the site is released, pages load the new one automatically. A tab you left open keeps running the old version until you reload; the site tells you when a newer one is ready and never reloads on its own.
What this proves, and what it does not
Working offline shows that HerePDF's tools do not need a server to do their job. It does not show that any other site's tools work the same way, and it does not replace judging the site itself: the code you store is whatever the site published when you visited. For how the privacy claim is built and tested, see client-side versus upload-based PDF tools, and before you send a finished file to someone else, the checklist for checking a PDF before you send it.
Everything described here runs in your browser. HerePDF does not send your files to a server, before or after you have gone offline.
Frequently asked questions
Do I need to install anything to use HerePDF offline?
No. Open the site once with a connection and wait for "Works offline: ready" in the footer. After that the tools, guides and pages open with the network off (OCR PDF is the one exception: it needs its own files, see the OCR answer below). Some browsers also offer an install option, which puts it on your home screen, but that is optional.
Are my PDFs saved on my device for offline use?
No. What is stored is the site itself: its pages and code, about 3 MB. The PDFs you open are processed in memory and discarded when you leave the page, online or offline.
Does OCR PDF work offline too?
Only after it has been used once while online. The OCR engine and each language's data are not part of the stored copy of the site; they are saved when you first use OCR on a page the offline copy already controls, so that means a later visit, not the visit that first stored the site. After that, the language you used works with the network off, until your browser clears it. A language you have not used yet needs a connection.
Why does the footer not say "ready"?
The site is still being stored in the background, or your browser is set to save data or is on a very slow connection, in which case the copy is not downloaded. Browsers without service workers, such as Firefox private windows, cannot store it at all. In each case the site works as an ordinary website.
Does going offline prove my files are safe?
It proves HerePDF does not need a server to do the job: a tool that keeps working with no connection cannot be sending your file anywhere while it works. It does not say anything about other sites, and the stored code is only as trustworthy as the site you got it from.