Compress PDF

How Compress PDF works

Most of the weight in a large PDF is pictures: scanned pages, photos and screenshots stored as JPEG images. This tool finds each of those images, scales it down if it is larger than needed and saves it again as a smaller JPEG. The text, fonts and vector drawings on the page are not touched, so words stay sharp and can still be selected and searched.

The three levels set how far it goes. Light keeps images up to 2,400 pixels on their long side at 80 percent JPEG quality, which suits documents that will be printed. Balanced keeps up to 1,600 pixels at 65 percent, which reads well on any screen. Strong keeps up to 1,100 pixels at 50 percent for the smallest file, which is fine for scans of typed pages but softens small print in photos.

After the images, the file itself is rewritten with qpdf, an open-source PDF toolkit compiled to WebAssembly: internal objects are packed together and every compressed stream is squeezed again at the highest setting. That part is lossless. If nothing gets smaller, for example because the PDF is all text, you get the original back unchanged rather than a bigger copy.

Images stored in other ways, such as lossless PNG-style images, CMYK images from print workflows and images with transparency, are left exactly as they are. That keeps the tool safe to use on any PDF, at the cost of smaller savings on files built mostly from those.

Compress PDF options explained

When to use it

Compress a PDF when it is too large for an email attachment, an upload portal or a job application form, when a scanned document came out at tens of megabytes, or when a report full of photos needs to load quickly on a phone.

Start with Balanced. If the file is still too large, run it again on Strong from the original, not from the compressed copy, so the images are only recompressed once.

About the PDF toolkit

Unlock, protect and flatten, and the final step of compression, use qpdf, a long-established open-source PDF toolkit that many desktop programs and servers rely on, compiled to WebAssembly so it runs in this tab. It loads the first time you use one of these tools, about 1.3 MB, and is cached. qpdf works on the internal structure of the file: it can encrypt and decrypt with the PDF standard's own methods, draw form fields into the page, and rewrite objects more compactly, all without re-rendering the pages. Because it runs on your device, passwords and the documents they protect never pass through a server, which is the point of protecting them in the first place.

Compress PDF troubleshooting

The PDF barely got smaller

It is probably mostly text or vector drawings, which are already compact, or its images are stored in a format this tool leaves alone. The result is the best that can be done without turning pages into pictures.

"returned unchanged"

Nothing could be made smaller, so the original file is offered back as it was instead of a larger copy.

The PDF is password protected

Encrypted PDFs cannot be read without the password. Remove it with Unlock PDF, compress the result, then protect it again if you need to.

How to use Compress PDF, step by step

1. Press "Choose PDF files" or drag PDFs onto the box.
2. Set the options if you need to; the defaults suit most uses.
3. Press "Compress PDF". The work happens on your device.
4. Save the result with its download button.

Is it safe to do this online?

With most online tools, "online" means your file is uploaded to a company's server, processed there and kept for a while before it is deleted. Here it is not. The page downloads the tool's code to your browser, and your file is read and processed inside the tab on your own device. It is never sent to TapToConvert or anyone else.

You can check this yourself: once the page and its engine have loaded, turn off Wi-Fi and the tool still works. That also means there is no queue, no daily limit and no file size cap set by a server; the only limit is the memory your browser gives a single tab.