Open a large PDF without it freezing or hanging

The quick way to open a big PDF smoothly

If a PDF makes your phone slow or your PDF app hang, read it in your web browser with a viewer that opens a file in small pieces:

1. Open the PDF Viewer in an up-to-date browser: Chrome or Samsung Internet on Android, Safari or Chrome on an iPhone, or Chrome, Edge, Firefox or Safari on a computer. There is nothing to install and no sign-up.
2. Tap Open a PDF and pick your file. On a computer you can also drag the PDF onto the page.
3. Wait for the first page. It shows as soon as it is drawn, and the others are drawn as you scroll. You don't have to wait for the whole file.
4. Jump, don't scroll. Type a page number in the page box, tap a picture in the side panel, or press the magnifier to search. See finding your page.
5. Stay on Fit width, where every PDF starts. Press the plus button only to read small print.

Your PDF is never uploaded. Your browser reads it from your own device, so there is no upload to wait for. If the reader you already use opens the file quickly, keep using it. This article is for the days it doesn't.

Why a big PDF makes a phone or computer hang

"Big" can mean four different things, and each slows a reader in its own way.

Many megabytes

Text takes very little room in a PDF. A scanned page is a photo of paper, so it takes far more. In our test files, a 14-page research paper was 992 KB, while a 42-page colour scan was 47.8 MB. A scanned book or a year of scanned bills can reach hundreds of megabytes (MB, the unit file sizes are counted in). The compressor's guide explains why PDFs get big.

Many pages

A court judgment, a textbook or a year of bank statements can run to hundreds of pages. That is more for a reader to keep track of, and a lot more scrolling for you.

Heavy pages

What is on each page matters as much as the file's size. A page that is one big, sharp photo takes longer to draw than a page of text. Very detailed drawings, such as maps or building plans, can take a while too.

Not enough memory

Memory (RAM) is the space a device uses for what it is working on right now. Phones have less of it than computers. Some readers load the whole file into memory before they show anything. For a very big file that can be too much, and you see a blank screen, a frozen app or a sudden close. That usually doesn't mean the file is damaged.

The cure is the same each time: load only what you are looking at.

What our viewer does differently, and how fast it was

Our viewer draws pages with pdf.js, the free, open-source PDF reader that Firefox also uses. It is built so a big file asks no more of your device than a small one:

• It reads in small pieces. It doesn't load the whole PDF into memory first, only the parts needed for the pages on your screen.
• It draws only the pages near you. Pages you scroll past are put away again, so only a few near your screen are kept drawn.
• It holds a place for every page. Until its picture is ready, a page shows as a blank sheet with its number, so the scrollbar and page jumps work from the start.
• It hands memory back. After you have read through a lot of a very large file, the viewer quietly opens it afresh in the background, which gives memory back to your device. You stay on the same page.

What we measured

We timed it in Chromium, the browser Google Chrome is built on, on our test computer. We opened each file six times and jumped to pages far into it. The table shows the quickest and slowest times.

The size of the file hardly matters: the 1,000-page scan opened about as quickly as the 42-page one, because only the pages you look at are read. What matters more is what is on each page. The guide has the full table for big files.

Treat these as the best case. Phones are usually slower than our test computer, and we have not timed real phones, so expect longer there.

Opening a big PDF on an Android phone or iPhone

First, check the whole file is on your phone

The most common reason a big PDF "won't open" is that it isn't all there.

• WhatsApp or Telegram: wait until the document has finished downloading in the chat.
• Email: download the attachment itself. A file saved from an email preview is often cut short.
• Google Drive: picking a Drive file may first bring a copy to your phone. For a big file that can take a while on mobile data, so use Wi-Fi if you can.
• The size: if the Files app shows 0 KB, or far less than you expected, the download stopped. Download it again.

Then open it

1. Open the PDF Viewer: in Chrome or Samsung Internet on Android, or in Safari or Chrome on an iPhone or iPad.
2. Tap Open a PDF and pick the file, for example from Downloads, or from the Files app on an iPhone.
3. Wait for the first page, then use the page box to go where you need.

We tested in Chromium with phone screen sizes copied on a computer, not on real phones, so these steps follow the viewer's own guide.

Habits that keep it smooth

• Close other tabs and apps first. They share the same memory.
• Keep the viewer on screen. If you leave for another app for long, the phone may reload the page to free memory. The viewer keeps nothing, so you would open the file again. Note your page number before you switch.
• Read at Fit width, and turn the phone sideways for bigger text.
• Zoom with the plus button, not by pinching. Pinching only stretches the page as a picture, so small text goes soft. On phones and tablets, a page zoomed in a long way is also drawn with fewer pixels to save memory, so it can look a little soft.

Get to the right page without scrolling through hundreds

Scrolling through 400 pages with your thumb is slow in any reader. These ways are quicker:

The page box counts from the first page of the file. A book's printed numbers can differ, because covers and contents pages often have none, or use i, ii, iii. Say a 600-page law book's index points to page 342, and typing 342 lands you two pages early. Now you know the gap is two pages, so add it each time.

In a long file, the pictures in the Pages tab appear a few at a time as you scroll the panel, so a box may be empty for a moment. They are made only while the main pages are not being drawn, so your reading stays smooth. That is normal.

Big scans: what search can and cannot do

Many of the biggest PDFs are scans: old records, textbooks, a whole file of certificates. A scanned page is a photo of paper, so the PDF holds the picture but not the letters. The viewer shows it sharply, but there is nothing to search or copy.

• "No text". When the viewer finds no text at all, the count says No text and a note says the file is most likely a scan.
• It stops and asks. Searching a long scan is slow, because every picture must be opened. After 20 pages without text, the viewer stops and asks first. Press Search every page to go on. On our 1,000-page scan, the search stopped in under 2 seconds, and searching all 1,000 pages took 28 to 44 seconds on our test computer.
• Mixed files. If the search stops but you know typed pages come later in the file, press Search every page. Otherwise those pages are not searched.

A big file with real text is usually much quicker to search, because there are no pictures to open. And the text of each page is read only once, so a second search in the same file is faster than the first.

The viewer doesn't do text recognition (OCR, software that reads the letters in a picture), so a scan stays a picture: easy to read, but not searchable. To find your way around a scanned book, use its bookmarks if it has them, the Pages tab and the page box. If you need real search, ask the sender for a typed copy. The guide's part on scanned PDFs shows how to tell whether a file is a scan.

If it is still slow, blank or won't open

Find your symptom, and try the fix beside it:

• Pages stay blank for a while. Pages that are big photos take longer to draw, more so on an older phone. Give it a moment, go back to Fit width, and close other tabs.
• The page goes blank, reloads or the browser closes. The phone has probably run short of memory. Close other apps and tabs, open the file again and read at Fit width. If it happens again, use a computer for this file.
• "This file can't be opened." The file is damaged, cut short, or not really a PDF. Download it again from where you got it.
• "This PDF couldn't be opened in this browser." Reload the page and try again, or try another up-to-date browser.
• A box asks for a password. Bank statements and salary slips often come locked. Type the password and press Open. It is used only on your device and is not kept.

If it is slow even so, the file may simply be too much for the device. Try a computer, or cut the file down, as the next part shows. The viewer's troubleshooting list covers every message.

When you need only part of it, or a smaller copy

The viewer only reads, so it can't make a file smaller. Two of our other tools can, and neither uploads your file.

You need only some pages

Use Split PDF to take out the pages you pick, or to cut a big book into chapters, then open the small file. It copies each page as it is, so nothing loses quality, and a few pages from a long book make a small file. See the three ways to split. A PDF locked with a password must be unlocked before it can be split. Organize PDF can remove pages you don't need.

You need every page, but smaller

The PDF compressor makes a file smaller. Scans shrink the most, because they are mostly pictures stored sharper than they need to be. Its guide suggests a computer for files over a few hundred megabytes, since a phone has less memory (see how light it is on your device).

Both, in order

For a huge scan, use a computer, since splitting and compressing both need memory. Split first, then compress each part. Afterwards, open the new file in the viewer and zoom in on the small print to check it is still easy to read. To email it, remember Gmail takes attachments up to 25 MB, and sends a bigger file as a Google Drive link instead.

Your own reader or ours: which one to use

The readers already on your devices are good, and many big files open fine in them: the PDF reader built into Chrome, Edge and Firefox, Preview on a Mac, Adobe Acrobat Reader. If yours opens the file quickly, there is no reason to switch.

Try our viewer when

• Your reader hangs. Pages stay blank, the app freezes or it closes on a big file.
• Your phone has no PDF app, or asks you to install one first.
• You need one page of a huge file now, and your reader is slow to get there. Here you type the page number and go.
• The big file is private, like a year of bank statements or a medical file. It is read on your device and never uploaded.

Use your own reader when

• You need to print, fill in a form or sign. The viewer only reads. The PDF is already on your device, so print it from your device's PDF app or your browser's own viewer.
• You need two big PDFs side by side. The viewer shows one PDF at a time, so open it in two tabs, keeping in mind that each tab uses memory of its own.

Some online viewers upload your file to a server first. For a file of hundreds of megabytes, that upload alone can take a long time on mobile data, before you see page one.

Questions people ask next

What is the biggest PDF the viewer can open?

We set no limit on size or pages. The real limit is your device's memory, and phones have less than computers. Our biggest test file was a 1,000-page scan of 1.11 GB, opened on a computer. We have not tested real phones.

Why is the page I jumped to blank for a moment?

The viewer draws only the pages near your screen. A page far away shows as a blank numbered sheet until its picture is ready, a moment later. Big photo pages take a little longer.

Does it remember where I stopped?

No. The viewer keeps nothing: not your file, your searches or your place. Note the page number before you close the tab.

Can I read a big PDF offline?

Yes. Load the viewer page while you are online. After that, most PDFs open even with Wi-Fi and mobile data off. A few files need an extra part of the reader, such as the fonts for Chinese or Japanese text, which comes from this website.