Why process files in your browser, and how to check it yourself

Two ways to do the same job

When a page says it can merge PDFs or compress an image, there are two possible designs. In the first, your file travels over the internet to the company's server, gets processed there, and the result comes back to your device. In the second, the page downloads the tool's code (JavaScript and a few libraries) and that code runs inside your browser, using your own device's memory and processor. The file never leaves it.

From the outside the two look almost identical: you pick a file, click a button and download the result. The difference is the path your document took. That is why it pays to know how to tell them apart instead of trusting a sentence on a landing page.

What uploading a document risks

Uploading a file means a copy exists outside your control, even if only temporarily. That copy crosses the network, sits on someone's disks and can end up in backups or logs. You don't need to suspect any particular company: the risk is structural. The longer and the farther a piece of data travels, the more chances there are that it is kept longer than intended, that access is misconfigured or that it leaks in an incident.

This matters most for certain files:

• Identity documents (ID card, passport, driver's license), which can be used to impersonate someone.
• Contracts, pay stubs, bank statements and tax returns.
• Medical results and certificates.
• Personal or family photos, especially of children.

If the processing happens on your device, that category of risk does not exist for the file itself: there is no outside copy to protect.

Test 1: use it without internet

This is the simplest check and the hardest to argue with. If a tool works offline, it cannot be sending your file anywhere while it works.

1. Open the tool, for example Compress image or Merge PDF, and wait for the page to finish loading.
2. Cut the connection: turn off wifi or switch on airplane mode.
3. Choose a file (a photo in Compress image, two PDFs in Merge PDF) and use the tool as usual.
4. Download the result.

If everything works, the processing does not depend on a server. One honest caveat: some tools download a library only when they need it, so a failure offline is not conclusive proof of the opposite. In that case, use the tool once with internet so all its parts load, then repeat the test after disconnecting. And if you reload or close the page while offline, it will ask the internet for its content again, so run the test without reloading.

Test 2: watch the Network tab while you process

The first test tells you the tool works without a server. This one lets you see with your own eyes what leaves your browser. Every modern desktop browser includes developer tools that log each network request.

1. Open the tool and press F12 (or Ctrl+Shift+I; on a Mac, Cmd+Option+I) to open the developer tools.
2. Go to the "Network" tab.
3. Click the clear icon to wipe the list of earlier requests.
4. Choose your file and process it, for example with Compress image.
5. Look through the list. Check the size or "Transferred" column and the method: a file upload would show up as a POST or PUT request with a size close to your file's.

On this site you should see nothing like that when you process a file. It is normal to see a small request of a few bytes: the anonymous statistics record described in the next section. You can click it and open the "Payload" tab: you will see data such as the tool name, the language or a result code, not the contents or the name of your file. If a request is ever far larger than what you were about to upload, that is when it is worth asking where it is going.

What ABC SyG stores, exactly

Processing in the browser does not mean the site records nothing. This is what our privacy policy says:

• Your files are not uploaded to our servers or sent to any third party. When you close the page, they are gone.
• There are no accounts, and we do not collect your name, your email or the content of your files.
• Like any website, the hosting provider records technical data in server logs, such as IP address, browser type and pages requested, to operate and protect the site.
• We record anonymous usage and error events: which tool and language, how many files and their approximate size range, how long it took, whether it worked, error codes, browser and operating system type, where the visit came from in general terms (search engine, social network, a link on another site or a direct visit), and whether you tap the link to the Android app on Google Play, without tying it to any person.
• We never record the names or contents of your files or texts. For these statistics we use no cookies or identifiers and we do not store your IP address: only a shortened version is used briefly to limit abuse. The records are deleted after 180 days.
• If your browser sends Do Not Track or Global Privacy Control, we record nothing.
• The tools do not set their own cookies. To remember your preferences, the site saves in your browser (local storage: no cookies, and nothing sent to any server) your light or dark theme and the settings or records of some tools and games; you can delete them whenever you like from your browser settings. Your files are never stored.

Advertising is a separate matter: the site uses Google AdSense, and Google and its partners may use cookies to show ads; where the law requires it, we ask for consent first. Ad cookies have nothing to do with your files, but you should know about them. The full policy is on the site's privacy page.

Example: preparing paperwork for an application without uploading it anywhere

Say a portal wants a single PDF with the front and back of your ID and a proof of address, plus a photo under a certain file size. With in-browser tools you can handle it like this:

1. In Compress image, choose the photos of the document, select "Target size", enter the maximum the portal requires and press "Compress". Compressing removes metadata such as camera model and GPS location.
2. In Merge PDF, add the PDF files with "Choose PDF files", order them with "Move up" and "Move down" and press "Merge PDF".
3. Download the result and check that everything is legible before sending it.

At no step did the contents of those documents pass through a server of the site. If you want to be sure, do it with wifi off after the page has loaded.

What this model does not guarantee

Processing in the browser removes a big risk, but not every risk, and it is worth saying so plainly:

• The site is still code your browser downloaded. If it changed behavior tomorrow, today's check would not cover the future; that is why the habit of glancing at the Network tab is worth more than a single check.
• If your device has malware or a browser extension that reads pages, that extension can see your files wherever they are processed. Review which extensions you have installed and disable the ones you don't use.
• A shared computer, or one without a screen lock, exposes your downloaded files like any other.
• Not being uploaded does not make the result safe to share: a merged PDF still contains everything the originals contained.

Good habits for sensitive documents

• Prefer tools that process in the browser, and verify with either of the two tests in this guide.
• Share only the minimum: if the application asks for the front of the ID, don't also send the back.
• If the recipient allows it, add a watermark stating the purpose of the copy to make misuse harder.
• Delete intermediate files from your downloads folder when you are done.
• Avoid public wifi for sending important documents, and keep your browser up to date.
• Be wary of tools that make you register for something as simple as merging two files.

Frequently asked questions