The PDF File Bigger Than the Universe
Technology and Scientific Thought
It All Started with a Tiny Tweet
The story began with a small tweet. Circulating across social media was a curious claim: the maximum size of a PDF file could be as large as 381 square kilometers. That’s roughly half the size of Germany or equivalent to the U.S. state of Iowa (though Germany is actually much larger—about 357,000 square kilometers).
This strange bit of trivia had been floating around online for years.
But software developer Alex Chan decided to look at it from a different perspective. He wanted to test it out for himself.
And what began as a bit of curiosity soon turned into an unbelievable discovery.
Alex Chan ended up creating a PDF file larger than the entire observable universe.
This is the story of that mind-blowing journey.
What’s a PDF, Anyway?
Most of us are familiar with PDFs — the Portable Document Format. It was invented back in 1993 by John Warnock, co-founder of Adobe.
The goal? To solve a frustrating problem: documents looked different on different computers, often with distorted graphics and layout. Warnock wanted a solution that would make documents appear exactly the same on screen and in print, no matter the device.
Legend has it, he sketched the idea on a napkin at a Silicon Valley restaurant. He called it the Camelot Project.
Within two years, that idea evolved into what we now know as the PDF format, and with it came Adobe Acrobat.
Using code, he began editing the PDF file by hand, breaking free from the rigid rules of Acrobat Reader. Interestingly, the limitations present in Acrobat didn’t exist in Apple’s Preview app.
In the beginning, PDF wasn’t very popular. The files were quite large, and in the 1990s, uploading or downloading big files took a long time. As a result, people found it more troublesome than helpful.
But things changed in 1996 when the Internal Revenue Service (IRS) of the United States chose PDF as the format for filing taxes. That decision marked a turning point. From then on, Americans were essentially required to use PDFs.
After 2008, the format’s popularity began to grow rapidly.
Today, everyone from artists to astronauts uses PDF files. In 2023 alone, an astonishing 2.5 trillion PDF documents were created. Most PDFs are of average size, but Alex Chan discovered a new kind of format—one with no limits.
Earlier, we mentioned the 381-kilometer limit. That number actually stems from a technical limitation within Adobe Acrobat Reader. It’s not a universal restriction, but rather a built-in boundary. Adobe Acrobat cannot create PDF files larger than 15 million inches—or about 381 kilometers—in width or height.
PDF’s success really began in 1996, when the Internal Revenue Service (IRS) in the United States adopted it as the official format for filing taxes. From that point on, Americans were essentially required to use PDFs.
But Alex Chan wasn’t satisfied. He realized that the limitations being discussed were specific to Adobe Acrobat—not to the PDF format itself. So, he began experimenting. Using code, he manually edited PDF files, breaking the rigid boundaries set by Acrobat Reader.
Interestingly, the same limitations didn’t exist in Apple’s Preview app. In Preview, you could create a file as large as you wanted. So, Alex pushed the boundaries—literally. He started with a page even larger than the size of Germany. Then, he gradually increased the dimensions of his PDF file.
Soon, his document reached a width of one trillion units. Given that one unit equals 1/72 of an inch, that comes out to about 352,778 kilometers—roughly the same as the distance from Earth to the Moon.
But Chan didn’t stop there. He kept experimenting. Eventually, he created a PDF file with a size of nearly 37 trillion light-years squared. While most of that file was just empty space, he still managed to create it. As Alex Chan himself put it, “I have to admit, most of it is empty space — but then again, so is the universe.”
For context, the diameter of our observable universe is about 93 billion light-years. In comparison, Alex’s PDF spans 37 trillion light-years squared. That means, in terms of area, his PDF is incomprehensibly larger than the visible universe.
Of course, Chan ended on a humorous note, saying, “Please don’t try to print it — the universe probably doesn’t have that much ink.”
