Compress PDF files without uploading

A PDF compressor that never uploads your files

PDFGuild compresses PDF files right inside your web browser, so they get smaller and the files never leave your device. Most online PDF compressors upload your file to their servers, shrink it there and send it back. PDFGuild does the same job on your own phone or computer instead. Your file is read, compressed and saved on your device, and it is never sent anywhere.

That one difference changes a lot. Private documents such as bank statements, salary slips, ID cards, medical reports and contracts stay with you. There is no upload to wait for, so big files finish sooner, even on a slow connection. And because we don't pay for servers that store and process files, we can keep the tool free, with no size limit, no sign-up and no watermark.

• 0files uploaded, ever
• 94%smaller: our sample scan, 9.96 MB to 563 KB
• 0.5 MBfor the tool, engine included (ads not counted)
• 1.1 GBscan compressed in our largest test

Why are some PDF files so big?

Text takes up very little room in a PDF: a full page of words often needs only a few kilobytes. When a PDF is several megabytes, the size almost always comes from what sits next to the text.

• Scans and photos of documents. A scanner saves every page as a picture. A colour A4 page scanned at 300 dpi is about 8.7 million pixels, and in our test files each scanned page took 1 to 2.5 MB. On a screen or an office printer, a quarter of those pixels, 150 per inch, already looks sharp.
• Photos pasted at full size. A photo from a 12-megapixel phone camera keeps all 12 million pixels when it is pasted into a document, even if it appears no bigger than a stamp.
• Copies of the same picture. Some programs store a logo or background again on every page instead of once for the whole file.
• Hidden extras. Editing programs leave behind page previews, private editing data and old versions of changed pages. None of it is visible, but all of it takes space.
• Loosely packed data. Some programs save text and drawings with weak compression, or none at all.

PDFGuild deals with each of these. It resizes oversized pictures, stores repeated pictures once, removes hidden extras and packs everything else tightly. Fonts are kept, because the text needs them to look right.

How PDFGuild compresses a PDF

When you open this page, your browser downloads a small compression engine: about 0.5 MB together with the rest of the page, not counting Google's ad code. The engine is written in Rust, a programming language known for speed and safety, and runs as WebAssembly, the technology browsers use to run fast programs securely. After your first visit, your browser keeps a copy, so the page opens almost instantly.

When you choose a PDF, the engine works through it in six steps:

1. It reads the file. The PDF is opened on your device. Common damage, such as a broken index that stops some tools from opening a file at all, is repaired along the way.
2. It measures every picture. PDFs often hold photos and scans stored much sharper than they appear on the page. The engine works out how large each picture is actually drawn, in pixels per inch (ppi), the same measure printers use.
3. It resizes oversized pictures. Pictures sharper than your chosen level are scaled down to it: 100 ppi for Smallest, 150 ppi for Recommended or 220 ppi for Best quality. They are saved again as JPEG at a matching quality. Charts, logos and screenshots with few colours are kept sharp with lossless compression instead.
4. It leaves text and drawings alone. Text, fonts, lines and vector drawings are never turned into pictures or blurred. They stay as crisp as in the original, and you can still search and copy the text.
5. It removes waste. Duplicate pictures are merged, data that nothing uses is removed, hidden page previews and editing leftovers are dropped, and the rest of the file is packed tightly.
6. It checks the result. For files up to 600 MB, the engine reads the new PDF back to make sure every page is still there. If the new file would not be smaller, you simply keep your original.

All of this happens in a background worker, separate from the page, so the page keeps responding while your file is processed. Each file gets a fresh worker that closes as soon as the file is done, which hands the memory it used straight back to your device.

How much smaller your PDF gets: real test results

Numbers matter more than promises, so here are real measurements. We compressed each file below at the Recommended level in Chromium, the open-source browser Google Chrome is built on, on our test computer. Times on your device may be shorter or longer.

The pattern is clear. Scans and photo-heavy PDFs shrink the most, often by three quarters or more, because they are mostly pictures stored sharper than they need to be. PDFs that are mostly text are already compact, so they shrink less.

We also test the extremes. A 477 MB scan was compressed in 106 seconds and a 1.1 GB scan in 266 seconds, both in Chromium on a desktop computer, with nothing uploaded. Our test set has 89 PDFs, including forms, links, bookmarks, maps, scans and whole books. All 86 that could be opened were compressed correctly, with every page and all text intact. The other three were a password-protected file and two damaged files, and for those the tool explains the problem instead of saving a broken copy.

Light on your phone or computer

A tool that runs in your browser should never slow your device down. PDFGuild is built to stay light, and we measured it in Chromium:

• About 0.5 MB to load. The tool, compression engine included, is smaller than a single photo from a phone camera; Google's ad code comes on top. After your first visit, it loads from your browser's cache.
• The compressor does nothing until you choose a file. With the page open and the engine ready, the compressor used 0.1% of one processor core in our test (ads not counted): practically nothing.
• Under 200 MB of memory for files up to 50 MB. The engine needed 8 MB for a 1 MB research paper, 59 MB for a 6 MB scan and 102 MB for a 48 MB, 42-page scan.
• One processor core, only for seconds. Compression runs on a single core in the background, so your other apps keep running smoothly. Most everyday files take one or two seconds.
• Memory handed back right away. When a file is done, its worker closes and the memory it used is released.

Very large files need more memory, about twice the file size, because the engine holds the original and the new copy while it works. Computers handle files up to about 1.8 GB. Phones have less memory, so we suggest a computer for files over a few hundred megabytes.

Private by design, and you can check it

"We delete your files after one hour" is a promise you have to trust. PDFGuild makes a stronger one: your files never leave your device in the first place, so there is nothing to delete.

A security rule called a Content Security Policy also lets the page contact only this site and Google's ad service, which shows the ads that keep the compressor free, and our code never gives your files to the ad code. The compression engine does not need the internet at all: once the page has loaded, you can switch off Wi-Fi and mobile data and keep compressing.

You don't have to take our word for it. On a computer, open your browser's developer tools (press F12 in Chrome or Edge), choose the Network tab and compress a file. You will see the page load its own files, a small request for the star ratings and Google's ads, and your PDF never sent while it is compressed. If you rate the tool, one more request carries only its name and the stars.

• No account and no sign-up.
• No cookies of our own and no analytics. Google's ads may use cookies; our privacy policy explains how.
• No copies of your files on anyone's server, because they are never uploaded.

That makes PDFGuild a good fit for documents you would rather not hand to a stranger: tax returns, bank statements, salary slips, Aadhaar, PAN and passport scans, medical reports, legal contracts and school records.

PDFGuild compared with upload-based tools

Here is how compressing on your own device compares with the usual way of compressing a PDF online:

Upload-based tools are not bad, and many are well made. But for private documents, very large files or slow connections, keeping the work on your own device is simply the better design.

Which compression level should you choose?

The three levels decide how sharp pictures stay. Text and drawings look the same at every level.

If you are not sure, start with Recommended. If the file is still too big, try Smallest. Your original file is never changed, so you can try each level and keep the copy you like best.

Compress a PDF on mobile and computer: Android, iPhone, Windows and Mac

PDFGuild runs in your web browser, so there is nothing to install: no app, no browser extension and no account. It works the same way on phones, tablets and computers.

• Android

  Open this page in Chrome, Samsung Internet or another up-to-date browser. Tap "Choose PDF files" and pick a PDF from your phone. The smaller copy is saved to your Downloads folder.

• iPhone and iPad

  Open this page in Safari or Chrome, tap "Choose PDF files" and pick a PDF from the Files app. The smaller copy usually goes to Downloads in the Files app.

• Windows, Mac, Linux, Chromebook

  Use Chrome, Edge, Firefox or Safari, and drop one or many PDFs onto the page. The smaller copies go to your Downloads folder.

You need an up-to-date browser, because the compressor runs as WebAssembly in a background worker, which all major browsers support. You can add several PDFs at once: they are compressed one after another, and each one gets its own Download button.

When a smaller PDF helps

• Email attachments. Gmail and Outlook.com both accept attachments up to 25 MB. A compressed PDF usually fits in one email instead of being turned into a cloud link.
• Online forms and portals. Job, exam, university, visa and government portals often accept PDFs only up to a fixed size, such as 100 KB, 500 KB or 2 MB. Compressing first saves you from the "file too large" error. If your papers are photos, turn photos of your papers into one PDF first.
• Sharing from your phone. Smaller files send faster on WhatsApp, Telegram and email, and use less mobile data for you and for the person receiving them.
• Storage space. Scanned documents add up quickly. Compressing a folder of scans can free gigabytes on your computer, phone or cloud storage.
• Websites. A smaller PDF on your website opens faster for visitors, especially on mobile networks.

Tips for the smallest possible PDF

1. Compress the original. Every round of compression loses a little picture detail, so start from the best copy you have.
2. Scan at 200 to 300 dpi. Higher scanner settings make huge files without making text easier to read. PDFGuild can bring an oversized scan down, but a sensible scan setting is the best start.
3. Scan text pages in grayscale. Letters, forms and receipts rarely need colour, and grayscale scans are much smaller. PDFGuild also stores pictures that have no colour as grayscale automatically.
4. Pick Smallest for tight limits. Smallest gives the biggest drop. When a form wants a file under an exact size, such as 150 KB, resize the PDF to any size in KB: it finds the sharpest version that fits.
5. Merge first, then compress. If a form wants one file, merge your PDFs into one file first and compress the result, so the size limit is checked on the very file you upload.
6. Check before you send. Open the compressed file and zoom in on the small print. If it is not clear enough, use Recommended instead.

How PDFGuild stays free

A typical online PDF tool is expensive to run. Every file has to be uploaded, processed on a server, stored for a while and sent back, and all of that costs money. PDFGuild skips it, because your own device does the work. Our running costs are a web address and one small server that sends out this page.

To cover those costs and keep building new tools, PDFGuild's pages load Google AdSense's ad code to show ads, kept separate from the tool. Our code never gives your files to the ad code, and we don't collect or sell personal data ourselves. Google's ad code may use cookies; our privacy policy explains how.

That is the whole business model: a fast, private tool that costs very little to run, paid for by a few ads and free for everyone.

PDF compression terms, explained

PPI (pixels per inch)

How many picture dots fill one inch of the page. More pixels per inch means a sharper picture and a bigger file. 150 ppi looks sharp on screens and office printers.

DPI (dots per inch)

The resolution setting on a scanner or printer. A page scanned at 300 dpi becomes a picture of 300 ppi inside the PDF.

JPEG

The usual format for photos and scans. It makes pictures much smaller by dropping fine detail the eye hardly notices. A quality setting decides how much is dropped.

Lossless compression

Packing data tighter without changing a single letter or pixel, like a ZIP file. PDFGuild uses it for text, drawings, charts and logos.

Metadata

Information stored with a file that the page never shows, such as the program that made it. Pictures often carry metadata of their own, and PDFGuild removes it.

WebAssembly

A way for browsers to run fast programs, written in languages such as Rust, safely inside the browser. It is what lets PDFGuild compress files without a server.

What it can't do yet

• PDFs that need a password to open. Remove the password from the PDF first with Unlock PDF, which needs the password, then compress the unlocked copy. PDFs that only restrict editing or printing are fine: the compressed copy opens without those restrictions.
• Digitally signed PDFs. Compressing changes the file, so a digital signature stops being valid. Keep the signed original for official use.
• Huge files on phones. Phones have less memory than computers. Use a computer for files over a few hundred megabytes.
• Text-only PDFs. They are already compact, so there is little left to remove.

More PDF tools are on the way, built the same private way.