- Ruth Kogan
- Dec 30, 2025
- 5 min read
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We create, save and share them every day but have you ever stopped to think about what a document actually is? A document contains our ideas, our data and our creative work. It's the proposal that lands a new client, the spreadsheet that tracks your budget or the presentation you create to rally your team.
Understanding what a document is and the various formats they can come in is essential for keeping everything organized. Picking the wrong file type can lead to formatting nightmares, huge file sizes or the dreaded cannot open file error message. This guide breaks down the basics of digital documents and walks you through the most common file types you need to know to work smarter.
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TL;DR: Common document file types
Not sure which file extension to use? Here is a quick cheat sheet to help you pick the right format for the job.
File type | Extension | Best used for | Why it works |
Word Document | .docx | Any type of written doc. | Easy to edit and widely compatible. |
Final versions, contracts | Preserves formatting exactly as intended. | ||
Text File | .txt | Coding, simple notes | Extremely lightweight with zero formatting. |
Spreadsheet | .xlsx, .csv | Data, budgets, lists | Organizes information into rows and columns. |
Presentation | .pptx | Slideshows, pitches | Designed for visual storytelling. |
Rich Text | .rtf | Basic formatted text | Sharable across different operating systems. |
HTML | .html | Web pages | The standard language for web browsers. |
What is a document?
In the simplest terms, a document is a record of information that can be retrieved later. Historically, this meant physical paper—scrolls, letters, and books. But today, when we ask the same question, we're almost always talking about a digital file.
A digital document is a self-contained unit of information saved on a computer or cloud storage. It can contain text, images, tables, charts and interactive elements. The beauty of digital documents is their flexibility. You can edit them endlessly, duplicate them instantly and send them halfway across the world in a split second. Whether it's a resume, a financial report or a blog post draft, if it stores information you created, it's a document.
6 common document file types you should know
Different tasks require different tools and that also means different file types. Here are the six main document file types that are most widely used.
01. The Word Document (.docx)
What is a Word document? Originally created by Microsoft Word, the .docx format has become the universal standard for word processing. It’s perfect for drafting content because it keeps your layout, fonts and images editable.
Use this format when a project is work in progress and ongoing. It allows you (and anyone you collaborate with) to make changes, add comments and track revisions as you work. While it’s the standard, it’s worth noting that if you open a .docx file on a different computer without the same fonts installed, the layout might shift slightly.
02. The PDF (.pdf)
PDF stands for Portable Document Format and "portable" is the operative word. A PDF is like a digital photocopy. It locks your formatting, fonts and images in place so that the document looks exactly the same on a smartphone, a tablet, or a laptop.
This is the go-to format for final versions of documents. You should understand how to create a PDF if you want to make resumes, contracts, invoices and manuals—basically anything you don't want people to accidentally change. It ensures your hard work looks professional no matter who opens it.
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03. The plain text file (.txt)
A .txt file is the simplest document type there is. It contains only raw text—no bold fonts, no italics, no images and no fancy layouts.
Why use it? Because it’s universally compatible. Every computer system can read a text file. It’s incredibly lightweight and is often used by developers for writing code, or by writers who want a distraction-free space to get words down without worrying about how they look.
04. The spreadsheet (.xlsx, .csv)
When you need to organize data, you need a spreadsheet. The standard Excel format (.xlsx) allows you to use complex formulas, create charts and format cells with colors and borders.
The simpler cousin is the .csv (Comma Separated Values) file. A CSV stores data in plain text, separating each value with a comma. It doesn't save formulas or formatting but it's the industry standard for moving data between different apps (like exporting your customer list from your email marketing tool to your CRM).
05. The presentation (.pptx)
If you need to stand up and present your ideas, a standard text document won't cut it. You need to understand how to put together a presentation. The .pptx format creates a visual-heavy document designed to be shown on a screen.
These documents handle text differently than a Word doc. Text is placed in boxes that you can move around freely, alongside images, videos and animations. This format focuses on visual impact rather than long-form reading.
Learn more about what a PPT file is.
06. The rich text format (.rtf)
Think of .rtf as the bridge between a plain text file and a full Word doc. It supports basic formatting like bold, italics and font sizes but it doesn't have the advanced features of a .docx file (like macros or complex drawing tools).
Its superpower is compatibility. You can open an RTF file in almost any word processor, whether it's Microsoft Word, Google Docs or Apple Pages. It’s a safe bet if you need to send a formatted document to someone and you aren't sure what software they have.
Learn more: What is an HTML file?
What is a document FAQ
Can I convert one file type to another?
Most software lets you Save As or Export"your document into a different format. For example, you can easily save a Word document (.docx) as a PDF to lock in your changes. Just be aware that going backwards (like converting a PDF back to Word) can sometimes result in messy formatting.
Why can't I open a specific document file?
This usually happens because you don't have the right software installed to read that specific file extension. For example, if you try to open a .psd (Photoshop) document but don't have Photoshop, your computer won't know what to do. A quick web search of the file extension will usually tell you which program you need.
Which document file type if best for printing?
PDF is the gold standard for printing. Because it locks your layout and fonts, you can be sure that what you see on your screen is exactly what will come out of the printer. Sending a Word doc to a print shop can be risky because their computer might shift your margins or substitute missing fonts.