Three processing paths compared
Where your PDF is processed: three routes
Choose a route. You'll then see where your file is processed and when you need an internet connection for it.
The illustration compares general types of tools. It doesn't check any file, program or service and makes no statements about individual providers.
All routes at a glance
- In the browser
- Installed program
- Online service
Browser-local, like this tool
- Checked in the program code
- Observed in a local test
The content of your PDF is processed in the browser on your device and is not uploaded. The browser loads the program components it needs from the website, some only when needed.
Load program components
The browser loads program files from the website, not your PDF.
Process in the browser
Your file is processed in memory on your device.
Save the result yourself
You download the new version and store it yourself.
- When first opened
- You need an internet connection to load the page and its program components. Some components are only loaded when they're needed.
- Page already open
- The processing itself runs in your browser. If a required program component hasn't been loaded yet, processing can fail without a connection.
- Starting without internet
- The website has no offline mode of its own. There's no promise that it will start without a connection.
- Sharing and cloud
- If you later send the result or put it in a synced folder, it leaves your device that way.
Browser-local means your file isn't uploaded. It doesn't mean the tool is available offline.
Installed program with offline use
- Not verified
A program on your computer can process PDFs without internet if it's already installed and set up. Whether every feature works offline depends on the program.
Set up the program
Installation and setup usually require a connection beforehand.
Process on your device
The program processes the file on your computer.
Save the result
The new file ends up wherever you choose.
- Setup
- Install and set up the program while you have internet. Then test it with a non-critical file.
- Processing
- Once the program is set up, processing runs on your device. Individual features may still require a connection.
- Starting without internet
- This is possible if the program is designed for it. Try it out before you rely on it.
- Sharing and cloud
- The same applies here: files in synced folders or in attachments leave your device.
Which features work offline is described in the documentation for each program. This overview doesn't describe any specific application.
Online service with upload
- Not verified
With an online service, you send your PDF to the provider you've chosen. The provider processes it on its server, and you download the result.
Upload PDF
Your file goes to the chosen provider.
Process on the server
Processing takes place outside your device.
Download result
You download the processed version from the service.
- When first opened
- You need internet for the service's website and for the upload.
- Processing
- The connection has to stay active because your file is processed by the provider.
- Starting without internet
- This route doesn't work without a connection.
- Sharing and cloud
- In addition to your own copies, the file is temporarily held by the provider. This overview can't assess for how long.
Before uploading sensitive documents, read the provider's information on storage and deletion. This overview hasn't checked any providers.
This selection only changes the display. It doesn't read any files, start any processing or save anything.
“Offline”, “without upload” and “without installation” refer to three different questions. Where is the document processed? Does software need to be installed? Does the route need an internet connection? A route can give a favorable answer to one of these questions but not to another. This website's PDF tool needs no installation and does not send your document to a server, but it relies on a connection to load its program components. An installed program can work without a network, but you have to set it up beforehand.
If you're not allowed to install software on a shared computer, you can use the browser-local route or an online service. If the document must not leave your device, services with server upload are ruled out. If you have no internet at all where you work, you need an installed program that you have set up and tested beforehand.
Shrinking job application documents without uploading them
You can do this. When you shrink certificates or your CV with the PDF tool here, the browser reads the file on your device, compresses a copy there and offers you the result to save. During compression, the document is not sent to any server. Submitting it later is a separate step: if you upload the finished PDF to a job application portal or attach it to an email, it goes to the recipient you choose. The guide shrink a job application PDF explains what matters when you compile and check your documents.
What the browser route requires
Use “Choose PDF” to select a file up to 50 MiB (52,428,800 bytes). Encrypted PDFs and files with a digital signature or certification are not compressed, and neither are files that show structural errors when they are read. A scanned signature, by contrast, is just an image and not a digital signature. The guide on signatures and forms explains why signed documents are a special case. You can start right away at process PDF locally in the browser.
What the browser still loads
For a browser to compress a PDF itself, it needs program code. It requests this code from the same website: the page, scripts, fonts, the compression module as WebAssembly and a decoder for the preview. The page requests some of these program files only when a function is needed for the first time. When that happens, your browser sends a request to the server, and the server returns the program file as a response. The page does not send the contents of your PDF along with these requests. The browser reads the selected file, passes a copy to its own background process on your device and creates the download file from it.
Is browser-local automatically offline?
No. Browser-local describes where your document is processed, not whether the page works without a network. The page has no offline mode of its own. Even if the page is already open, a program component that hasn't loaded yet may be missing as soon as the connection drops. There is no promise that the page will start again without internet after you restart the browser. So plan on having a connection for this route.
The page current file processing in the browser explains in detail what happens to your document, the program components loaded on demand and the finished result.
When there really is no internet
Without a connection, you need a program that is already installed on your computer and performs the compression itself. This website's PDF tool doesn't qualify, because it loads its program components from the network. With installed programs, it helps to distinguish three phases: downloading and installing, any sign-in or license activation, and finally the actual offline processing of your documents. “Offline” refers only to the last phase. Complete the first two while you still have a network connection.
In addition, a manufacturer's offline claim doesn't automatically mean that every function works without a network. With some programs, stronger compression levels or processing several files at once require an account or a paid version. Only a test run can reliably show whether your program starts without a connection after a restart and applies exactly the setting you need.
Windows: PDF24 Creator
The manufacturer offers PDF24 Creator as a desktop program for Windows 10 and 11 and lists compressing without internet among its features. According to the manufacturer's website, you wait until the installer has fully downloaded, open the downloaded file, follow the setup and then launch the program via the desktop icon. The guide Windows offline routes compares other options on Windows, including some that need no installation.
Can I use PDF24 Creator offline on Mac or Linux?
No. According to the manufacturer, PDF24 Creator is only available for Windows, and the FAQ on the manufacturer's website explicitly excludes Mac and Linux. On the Mac, use the Preview app instead, which is part of macOS. The next section explains how to export a file there.
Mac: Preview
Apple describes the process in the Preview help for macOS Tahoe 26:
- Open the PDF in Preview.
- Choose “File” > “Export”.
- Under “Quartz Filter”, choose “Reduce File Size”.
- Give the copy a new name and click “Save”.
Apple points out that image quality and final size depend on the options you choose. If Preview asks whether to replace an existing file, cancel and change the name under “Export As” so that your original file is preserved. The guide use Mac Preview explains how to check the copy afterwards.
Test it before you need it
- Install the program and complete any required sign-in or activation while you have internet.
- Disconnect, for example by turning on airplane mode, and restart the program.
- Compress a non-critical PDF with exactly the setting you will need later.
- Open the saved result and check its size and legibility.
If this works, you know that this route works without a network on your computer as it is currently set up. After major updates, it may be worth running another test.
Originals, downloads and shared devices
When you compress a file, the page offers you the result as a new file to save. Your original file remains unchanged in its current location. If the tool doesn't find a valid smaller version, you get the original back, and the savings are 0 bytes. As soon as you save the result, there is at least one additional file on the device besides the original, usually in the Downloads folder or in the location you choose when saving. If you download more than once, there may be several copies. If the storage location is connected to a cloud account and syncing is active, the saved result may also be transferred there without you deliberately uploading anything. So processing a file locally doesn't mean there is only one copy of it.
Does Reset delete the saved PDF on my hard drive?
No. “Reset” and “Edit a new file” end any processing in progress, clear the file selection and display, and invalidate the download link for the result on the page. Files you've already saved stay on your hard drive, as do the original and copies in synced folders. Closing the tab also ends any processing in progress. During processing, your PDF is necessarily held in the memory of the browser and the background process. The tool doesn't permanently store the content, the file name or any history in the browser, not even in a browser database. Apart from that, the only things the page remembers in local storage are your color scheme and, as a separate entry, your choice regarding analytics and advertising. This choice is no longer taken into account after 180 days or if its content is invalid. The entry itself isn't deleted automatically: it remains until you choose again or delete this site's website data in your browser. Reset isn't a secure deletion from memory or from the hard drive.
Cleaning up on a shared computer
- Open the saved copy and check all pages and small print before you delete anything.
- Before saving, set where the browser saves downloads, or have it ask you for the storage location with every download.
- Check whether the Downloads, Desktop or Documents folder is synced with a cloud account, and don't save sensitive copies there.
- After sending, delete your saved copies, delete the original if you brought it onto the computer only for this purpose, and empty the Recycle Bin.
- Remove the entry from the browser's download list and sign out of portals and email accounts.
- If the computer belongs to an institution or your employer, their rules for downloads and storage locations apply.
Even deleted files are not always permanently removed. For very sensitive documents, a device of your own that only you control is the better choice. The guide compress PDF without quality loss explains what to look for when you compare the original and the result.
Questions to ask for sensitive documents
Whether it's a doctor's letter, a contract or a job application, choosing a tool answers only part of the question of who gets to see your document. These questions help you make a deliberate decision:
- Where is the file actually processed: on your device or on a server? For online services, read what the provider states about upload, storage and deletion.
- Who controls the device? Your own computer is not the same as a shared computer or one managed by a company.
- Where does the result end up, and is that location synced or backed up?
- Are you allowed to use the tool for these documents? Internal rules may apply to work documents.
- How will the document later reach the recipient, and is that route appropriate for its content?
Does local processing prove GDPR (DSGVO) compliance?
No. Your document staying on the device during compression is a technical property of this one step. Whether a process as a whole complies with data protection law depends on other factors: who is responsible for the data, which rules apply in your organization, which device you work on and how you pass on the result. This guide cannot replace a legal assessment.
Even so, local processing offers a concrete benefit. It removes one transfer from the process, because you don't have to send the document to anyone for the compression itself. However, it does not protect against risks on the device, such as someone else accessing your folders. That's why your choice of tool, storage location and sending method all belong in the same decision.