← Back to Help Center / Source formats, limits, and pricing

Source formats, limits, and pricing

This page lists the current Content Source limits and rules.

Supported file types

You can upload:

  • DOCX
  • PDF (text will be extracted; images are ignored)
  • EPUB
  • TXT
  • RTF
  • ODT / FODT
  • HTML
  • Markdown

Upload limits

  • Max file size: 10MB per file
  • Max files per source: 20 files
  • Word count per source (across all files):
    • Minimum: 5,000 words
    • Maximum: 500,000 words

Tip: If you have more than 500,000 words, split your material into multiple sources and attach up to 3 sources per book project.

How sources work

Sources act as a knowledge base for your book—not as a blueprint. Youbooks draws facts, examples, and insights from your sources, but your prompt determines the topic and structure.

Example: If you write a book about boats and attach a source about marine wildlife, Youbooks will pull in relevant animal facts where they naturally fit (e.g., dolphins near harbors), but won't turn your boat book into a wildlife guide.

This design gives you control. You can upload large, broad sources without worrying that off-topic content will derail your book. The prompt is always the steering wheel.

What sources can't do:

  • Finish a half-written manuscript
  • Rewrite or expand an existing book
  • Override the topic you specify in your prompt

If you need those capabilities, consider using your existing draft as reference material while writing a fresh book on the same subject.

Language matching

Sources should be in the same language as the book you want to write. If they don’t match, the source will be much less useful.

Links inside sources

If your files contain links/citations:

  • Youbooks does not click or follow those links.
  • Your source must include the actual content (not just references to it).

Pricing: creating sources

Creating a source costs:

  • 1 credit per uploaded word (one-time fee)

Using the source in book projects does not cost extra credits.

Need help?

Use the support chat widget (bottom-right in the app), or email master@youbooks.com.

If you’re asking about a specific book, include your Project ID (you’ll find it on the book’s page).