Every document starts with a choice of format, even if the choice is made by default. The format decides who can open the file, whether the layout survives, how easy it is to edit and whether it will still be readable in ten years. Choosing deliberately saves time and avoids conversions later.
This article compares the formats people use most often for reading and writing and suggests when each one fits.
Plain text (.txt)
Plain text is the simplest format: characters and line breaks, nothing else. Almost every device and program can open it, and it compresses and searches well. It is ideal for notes, logs, data exports and drafts where structure does not matter.
Its limits are equally clear. There are no headings, links, images or emphasis beyond what you type by convention. Pay attention to the character encoding; UTF-8 is the safest default because it can represent text in virtually any language.
Markdown (.md)
Markdown is plain text with lightweight conventions: # for headings, asterisks for emphasis, hyphens for lists. The source stays readable as-is and can be converted to HTML, PDF or word-processor files with many free tools.
Markdown works well for documentation, README files, notes and blog drafts, especially when files are kept in version control. Be aware that several Markdown variants exist, so tables, footnotes and other extensions may render differently between tools.
PDF is designed to look the same everywhere. Fonts, page size and layout are fixed, which makes it the standard choice for forms, printed material, papers and anything that will be cited by page number. The archival profile PDF/A restricts features that could make a file unreadable later, such as external font dependencies.
The trade-offs are editing and small screens. PDFs are hard to modify without the source file, and fixed pages do not adapt to phones. Accessibility depends on how the file was produced: a tagged PDF with real text and a logical reading order works with screen readers, while a scanned image without OCR does not.
EPUB
EPUB is the open standard for ebooks. Internally it is a package of HTML, CSS and metadata, so text reflows to fit any screen and readers can change font size. That makes it the most comfortable format for long reading on phones, tablets and e-readers.
EPUB is less suitable when exact layout matters, such as complex tables, equations or page-referenced citations. Many digitized public-domain books are offered in both EPUB and PDF so readers can choose.
Word-processor files (.docx, .odt)
DOCX and the OpenDocument format ODT are best for documents that several people will edit, comment on and track changes in. Both are based on published specifications, and ODT is an international standard. Layout can shift slightly between programs, so convert to PDF when the final version is ready to distribute.
HTML
HTML is the format of the web. It handles links, images, headings and accessibility features well, and it reflows on any screen. For content that will be published online or read in a browser, HTML is usually the target, often generated from Markdown.
A quick decision guide
| Need | Good choice |
|---|---|
| Quick notes, data, logs | Plain text |
| Documentation and drafts in version control | Markdown |
| Fixed layout, printing, citation by page | PDF (PDF/A for archiving) |
| Long-form reading on small screens | EPUB |
| Collaborative editing with comments | DOCX or ODT |
| Publishing on the web | HTML |
Keep a source and an output
A useful habit is to keep one editable source file and generate other formats from it. For example, write in Markdown or ODT and export to PDF and EPUB. When something changes, you edit the source once and regenerate the outputs instead of fixing several copies by hand.
Key takeaways
- Plain text and Markdown are the most durable and easiest to edit.
- PDF preserves layout; EPUB and HTML adapt to the screen.
- Use word-processor formats for collaboration, then export a fixed version.
- Keep one source file and generate the other formats from it.