PDF, DOCX, JPG, PNG, TXT: File Formats Explained
Every file format was designed for a specific purpose. Understanding what each format is good at — and where it falls short — helps you choose the right format and know when to convert.
If you have ever wondered why some files end in .pdf, others in .docx, and others in .jpg, the answer lies in the different purposes these formats serve. Each was designed with specific use cases in mind, and understanding them helps you choose the right format for every situation — and know when converting between formats makes sense.
PDF (Portable Document Format)
Created by Adobe in the early 1990s, PDF was designed to solve a specific problem: documents looked different on different computers because they used different fonts, different versions of software, and different operating systems. PDF solved this by creating a frozen visual snapshot of a document — a format that presents identically on any device.
Strengths: Universal compatibility, consistent appearance everywhere, difficult to accidentally edit, excellent for printing, supports embedded fonts and images, can contain hyperlinks and interactive elements.
Weaknesses: Not designed for editing — changing content in a PDF requires specialist software. Can produce large files for image-heavy documents.
Best for: Final documents ready to share or submit — contracts, invoices, reports, CVs, application forms, publications, certificates, and anything that needs to be printed.
When to convert away from PDF: When you need to edit the content, convert to Word (DOCX). When you need images of pages, convert to JPG. When you only need the text, convert to TXT.
DOCX (Microsoft Word Document)
DOCX became the default Word format in 2007, replacing the older .doc format. It is an XML-based format stored in a ZIP archive, which means it stores document content in a structured, human-readable way. DOCX was designed for authoring and editing — it is the working format for word processing.
Strengths: Fully editable, excellent formatting tools, supports styles and templates, good for collaboration (tracked changes, comments), compatible with multiple applications beyond Microsoft Word.
Weaknesses: Appearance varies slightly between applications and operating systems — a DOCX created in Word may look slightly different in Google Docs or LibreOffice. Not ideal for sharing final documents.
Best for: Drafting and editing documents, collaborative writing, templates, and any document you are still working on. DOCX is the working format; PDF is the sharing format.
When to convert away from DOCX: When a document is finished and ready to share, convert to PDF.
JPG / JPEG (Joint Photographic Experts Group)
JPG is the world's most widely used image format, particularly for photographs. It was developed in 1992 specifically for compressing photographic images efficiently. JPG uses what is called "lossy compression" — it permanently discards some image data (in ways that are mostly imperceptible to the human eye) to achieve dramatically smaller file sizes.
Strengths: Very small file sizes relative to image quality. Universally supported across every platform, browser, and application. Excellent for photographs and realistic images.
Weaknesses: Lossy — each save degrades quality slightly. Does not support transparency. Not ideal for images with sharp edges, flat colours, or text (logos, screenshots, graphics).
Best for: Photographs, product images, social media photos, any realistic image where small file size is more important than pixel-perfect quality.
When to convert away from JPG: When you need transparency support or plan to edit the image multiple times, convert to PNG. When you need the image embedded in a document for sharing, convert to PDF.
PNG (Portable Network Graphics)
PNG was created in 1996 as a patent-free alternative to the GIF format, with the added benefit of much better compression for complex images. PNG uses lossless compression — every pixel is preserved exactly, no matter how many times the file is saved. PNG also introduced 8-bit transparency (alpha channel), making it possible to have images with smooth transparent backgrounds.
Strengths: Lossless — no quality degradation with repeated saves. Supports transparency. Excellent for graphics with sharp edges, flat colours, and text. Ideal for logos, icons, screenshots, and web graphics.
Weaknesses: Larger file sizes than JPG for photographic content. Not suitable for print workflows that require CMYK colour (print uses CYMK, PNG is RGB).
Best for: Logos, icons, app graphics, website images, screenshots, any image with transparency, and any graphic you will edit multiple times.
When to convert away from PNG: When you need smaller file sizes for photos and transparency is not needed, convert to JPG. When you need the image in a document, convert to PDF.
TXT (Plain Text)
A .txt file contains nothing but raw text characters encoded in a standard format (usually UTF-8 or ASCII). There is no formatting, no fonts, no images, no metadata — just the characters themselves. This makes TXT the most universally readable format in existence: any device, operating system, or software can open a text file.
Strengths: Universally compatible — readable on any device without any software. Tiny file sizes. Human-readable without any software. Easy to process programmatically.
Weaknesses: No formatting whatsoever. No bold, no headings, no images, no tables. Purely linear text.
Best for: Notes, configuration files, log files, code, data exports, and any content that needs to be processed by other software or read in any environment.
When to convert away from TXT: When you need formatting and structure, convert to PDF or DOCX. When you need to share it universally in a printable format, PDF is the right destination.