Last Updated: 14 Oct, 2025
The Portable Document Format has been around since 1993, and in the fast-moving world of digital technology, that makes it practically ancient. Yet despite the emergence of sleeker alternatives like HTML5, EPUB3, and image-based formats like WebP, PDFs continue to dominate professional document sharing. But is this dominance justified by actual performance, or are we simply stuck in our ways?
The Contenders: Understanding Each Format
Before diving into benchmarks, let’s establish what we’re comparing.
- PDF (Portable Document Format) was designed to present documents consistently across any device or operating system. Its core strength lies in preserving exact layout, fonts, and formatting regardless of where you open it.
- HTML5 represents the modern web standard. It’s responsive, searchable, and can adapt to any screen size. When we talk about HTML documents, we’re really discussing self-contained HTML files with embedded CSS and potentially JavaScript.
- EPUB3 evolved as the publishing industry’s answer to digital books. It combines HTML, CSS, and XML in a compressed package designed specifically for reflowable text content that adapts to different reading devices.
- WebP documents might seem like an odd inclusion, but many organizations have started converting multi-page documents into WebP image sequences for web delivery, capitalizing on WebP’s superior compression compared to traditional image formats.
1. File Size: The Compression Showdown
Determine which format is the most efficient for storage and transfer.
| No. | Format | Average File Size (10-Page Doc) | Notes |
|---|---|---|---|
| 1 | PDF (Optimized) | 1.2 MB | Used “Reduced Size” export in Acrobat. |
| 2 | HTML + Assets | ~900 KB | HTML file is tiny, but images and CSS add up. |
| 3 | EPUB | 950 KB | Internally structured like a zipped HTML website. |
| 4 | WebP (as a document) | 5.5 MB | Each page exported as a WebP image. File size is huge. |
Analysis: While a well-optimized HTML bundle can be slightly smaller, a modern PDF holds its own remarkably well. The key takeaway is that EPUB and PDF are in the same league for mixed-content documents. The WebP “document” approach fails here because it’s not a true document format—it sacrifices all the intelligence of text and vector data for a single, large image file.
2. File Size & Loading Speed
Measure how quickly a user can see and interact with the content on a standard laptop and a mobile device.
- PDF: File sizes can be large, especially with high-resolution images. However, modern PDF optimization tools can significantly compress files. A well-optimized PDF loads instantly offline. Online, it can be slower than HTML as the entire file often needs to load before it can be rendered in a browser viewer.
- HTML: Winner (for online viewing). HTML pages load progressively, meaning you see content as it arrives. Combined with optimized images (like WebP!), it provides the fastest web experience.
- EPUB: Generally very small file sizes because they are primarily text-based. They load almost instantly on e-readers.
- WebP: As an image format, WebP offers file sizes that are roughly 25-35% smaller than equivalent JPEGs or PNGs, which directly contributes to faster HTML page loads.
Analysis: HTML is the clear speed champion for on-screen consumption, thanks to progressive rendering. However, this speed comes with a caveat: it assumes a stable internet connection for all assets. A PDF can be fully available offline the moment it’s downloaded. EPUB performs well within its native environment (e-reader apps).
3. Accessibility: Reading for Everyone
Modern accessibility requirements demand documents work with screen readers and assistive technologies.
- PDF: Modern PDFs have come a long way. “Tagged PDFs” contain an underlying structure that allows screen readers to navigate headings, paragraphs, and image descriptions logically. However, creating a truly accessible PDF requires extra effort from the author.
- HTML: Winner. When coded properly with semantic tags (<‘h1>, <‘p>, <‘nav>, etc.), HTML is inherently accessible. It’s the native language of web accessibility tools.
- EPUB: Built on HTML, EPUBs are also highly accessible and work seamlessly with the accessibility features built into e-readers and mobile operating systems.
- WebP: Fail accessibility entirely. Converting pages to images removes all text structure, making screen readers useless. This alone disqualifies WebP for any organization committed to inclusive design.
Analysis: While PDFs can be made accessible, HTML and EPUB are generally more accessible out of the box.
4. Visual Fidelity & Consistency
- PDF: Winner. This is the PDF’s signature strength. A PDF is a digital snapshot. Fonts, images, and formatting are locked in place. This is non-negotiable for contracts, official forms, invoices, academic papers, and print-ready designs where a misplaced line or altered font could change the meaning or legality.
- HTML: Good, but inconsistent by design. An HTML document will look different on your phone versus your desktop. While this is a feature for web browsing (responsiveness), it’s a bug for documents that require a static, official layout.
- EPUB: Similar to HTML, it prioritizes readability over a fixed layout. Great for a novel, but terrible for a visually complex textbook or a resume where formatting is part of the presentation.
- WebP: Not applicable. It’s just an image; it doesn’t contain structured text or layouts.
Analysis: For any document where design is non-negotiable—such as a legal contract, annual report, architectural blueprint, or academic paper—PDF is the undisputed king. HTML and EPUB prioritize adaptability over fidelity.
5. Interactivity & Security
Security features often determine format choice in professional environments.
- PDF: Winner (for document-centric features). PDFs support a rich set of interactive features unavailable in other formats, including fillable forms, digital signatures, and password protection with granular permissions (e.g., allow viewing but not printing). This level of security and functionality is crucial for business and government.
- HTML: Highly interactive through JavaScript, but this interactivity is web-based (animations, application-like behavior). It lacks built-in features for things like legally binding digital signatures in a self-contained file.
- EPUB: Supports basic interactivity like hyperlinks and annotations but lacks the robust form-filling and security features of a PDF.
- WebP: images offer no document-level security features. While you can apply web-based access controls, the images themselves contain no protection mechanisms once downloaded.
Analysis: For secure, interactive documents like applications or contracts, the PDF is unparalleled. The other formats lack meaningful security features for business use cases.
6. Cross-Platform Compatibility
This measures how a file behaves across different operating systems and devices.
- PDF: Winner. The ‘P’ in PDF stands for Portable. It was built from the ground up to be independent of software, hardware, and operating systems. A PDF opened on a Mac, Windows PC, or Android phone will look identical. Most browsers and operating systems now include native PDF readers, making it truly universal.
- HTML: While accessible on any device with a web browser, its appearance is not consistent. Different browsers (Chrome, Safari, Firefox) can render the same code slightly differently, and the responsive design intentionally changes the layout based on screen size. It’s universally accessible but not visually consistent.
- EPUB: It has excellent compatibility within its intended ecosystem of e-readers and reading apps (like Apple Books, Kobo, etc.). However, it is not natively supported by web browsers or most desktop operating systems without dedicated software.
- WebP: As a modern image format, its compatibility is tied to browser and software updates. While supported by all major current browsers, it may not work in older browser versions or specific non-web software (e.g., older photo editors).
Analysis: For guaranteed visual consistency across every conceivable platform, PDF is the undisputed champion.
The Verdict: When to Use Which Format
There is no single “best” format. The right choice depends entirely on your goal.
- Use PDF when: You need a digital master copy. Think contracts, invoices, resumes, academic papers, manuals, and anything destined for print. Its superpower is preserving the layout.
- Use HTML when: You are building a website or web application. Its superpower is its responsive and dynamic nature.
- Use EPUB when: You are creating an e-book or a long-form text document for reading on various devices. Its superpower is reflowable text for maximum readability.
- Use WebP when: You need to optimize images on your website. It’s not a document format but a crucial component of a fast HTML experience.
The PDF isn’t competing with HTML or EPUB; it’s serving a different, and equally important, purpose. While HTML gives us fluid access to information, the PDF provides a stable, reliable, and universal snapshot of it. In a world of constant digital change, that kind of permanence still matters.
Conclusion: PDF is a Specialist
The performance benchmarks reveal a clear truth: the PDF is not obsolete. It is a specialized tool that excels at its primary job: preservation and universal presentation. While HTML may load faster in a browser and EPUB may be more comfortable to read in bed, neither can guarantee the ironclad visual consistency of a PDF. In a world where digital trust and design integrity are often crucial, the PDF remains not just relevant, but essential.
FAQ
Q1: Is PDF better than HTML for my website’s blog posts?
A: No, HTML is superior for SEO and user engagement on websites, while PDF excels for preserving formal document layouts.
Q2: Can an EPUB file maintain a complex layout like a PDF?
A: No, standard EPUB is designed for reflowable text, whereas PDF is the definitive choice for fixed, complex layouts.
Q3: Why would I use a PDF when a WebP image loads faster?
A: A PDF preserves selectable text and vector graphics, while a WebP is just a static, unsearchable image.
Q4: Is the PDF format still being improved and updated?
A: Yes, the PDF specification is actively maintained (ISO 32000) with modern features like improved accessibility and security.
Q5: For a legal contract, which format is the most reliable?
A: PDF is the undisputed standard for legal documents due to its universal consistency and integrity.