Upload a PDF and get a natural AI audiobook in seconds. Multi-column layouts, academic papers, textbooks — all handled automatically. No signup, no limits.
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Supports PDF, EPUB, DOCX, TXT, MD, HTML
Purpose-built for PDFs — handles layouts that break every other converter.
Multi-Column PDFs
Two-column research papers, three-column newsletters, mixed layouts with figures and tables. CastReader detects column structure and reads in the correct order. Headers, footers, page numbers, and figure captions are automatically filtered out.
Textbook Ready
Upload a textbook PDF and listen to it on the bus. CastReader preserves chapter structure, skips formatting artifacts, and handles the complex layouts that textbook publishers love. Each chapter becomes a separate audio track you can download.
40+ Languages
Upload a PDF in French, Japanese, German, or Arabic. CastReader auto-detects the language and uses a native AI voice. Perfect for language learners — read along in the PDF while listening to correct pronunciation.
No Software
Open this page, drop your PDF, listen. Works on any device with a browser — Chromebooks, school laptops, library computers. No desktop software to install, no plugins, no account to create.
PDFs are the most common document format on the internet — and the hardest to convert to audio. The reason is simple: a PDF is a visual format, not a text format. It describes where ink goes on a page. A two-column academic paper is just coordinates and glyphs. A scanned textbook is literally a stack of images. Most 'PDF to audio' tools don't actually handle any of this — they call a basic text extraction library, get garbled output, and feed it to a TTS engine. The result sounds like someone reading a phone book.
CastReader's PDF pipeline is different. It uses a multi-pass extraction process: first, it detects the page layout (single column, two-column, mixed). Then it reads text in the correct order — left column before right column, body text before footnotes. It identifies and strips headers, footers, page numbers, running heads, and figure captions. For scanned PDFs, it runs OCR. The output is clean, ordered paragraphs ready for the TTS engine.
The TTS engine itself uses Kokoro, an open-source neural voice model that produces speech natural enough for hour-long listening. It's not a robotic voice from 2018 — it handles emphasis, pauses, and sentence flow in a way that makes academic papers actually listenable. You can download the result as MP3 and listen on your phone, in your car, or on any audio player.
Who converts PDFs to audiobooks? More people than you'd expect. Graduate students listen to research papers during their commute — reading 20 papers a week on screen causes eye strain; listening to 10 of them while walking is sustainable. Law students convert casebook chapters to audio for review. Medical residents listen to clinical guidelines between shifts. Language learners upload foreign-language PDFs and listen along while reading. Teachers create audio versions of reading assignments for students with dyslexia or visual impairments.
The alternatives are expensive. NaturalReader charges $60/year for PDF upload. Speechify charges $139/year. Adobe Acrobat's built-in 'Read Aloud' uses the old robotic system voice and can't handle two-column layouts. Voice Dream Reader is $15 and iOS-only. CastReader is free — no daily limit, no page cap, no signup. Upload a 500-page textbook and it works the same as a 2-page handout.
For PDFs you access regularly online — academic databases, government documents, company reports — consider installing the free CastReader Chrome extension. Instead of downloading and uploading, it reads the PDF directly in your browser tab with paragraph highlighting and speed control. One click, instant playback.
Common questions about converting PDFs to audio
Yes. Upload any PDF — textbooks, research papers, reports, novels, manuals — and CastReader converts it to natural AI audio for free. No signup, no page limit, no daily cap. Other tools like NaturalReader ($60/yr) and Speechify ($139/yr) charge for this feature.
Yes. CastReader's PDF pipeline detects multi-column layouts and reads text in the correct order (left column first, then right). It also filters out headers, footers, page numbers, figure captions, and table labels so the narrator reads only the actual content.
CastReader runs OCR on scanned PDFs to extract text from page images. Results are best with clear, high-resolution scans. Handwritten documents and very old/degraded scans may have limited accuracy. For best results, use PDFs with selectable text.
Yes. After your PDF is processed, each chapter becomes a separate audio track. You can play them in the browser or download as MP3 files for offline listening on your phone, car, or any audio player.
Most PDFs process in under 30 seconds. A 500-page textbook might take a minute or two. You'll see a progress indicator, and the reader opens automatically when processing is complete.
Significantly. Adobe's built-in 'Read Aloud' uses old system voices (robotic and unnatural), can't handle multi-column layouts, and reads page numbers and headers aloud. CastReader uses neural AI voices, detects layout structure, filters noise, and lets you download the audio as MP3.
NaturalReader charges $60/year for PDF upload. Speechify charges $139/year. CastReader is free. Voice quality is comparable — all three use neural AI voices. CastReader's additional advantage: the free Chrome extension reads PDFs directly in your browser tab without downloading, and works on sites that block other tools.
Absolutely. Upload a PDF in your target language — French, Japanese, Spanish, Arabic, or 40+ others. CastReader auto-detects the language and uses a native AI voice. Read along in the PDF while listening for pronunciation and comprehension practice.
Yes. Your PDF is processed on our servers for text extraction and audio generation, then available only to you. We don't share, sell, or use your documents for training. No account required means no tracking.
Up to 100MB. For very long PDFs, the system processes them chapter by chapter. Each chapter becomes a separate audio track you can play or download independently.
Yes — install the free CastReader Chrome extension. It reads PDFs open in your browser tab directly, with paragraph highlighting and speed control. No downloading, no uploading. Perfect for academic databases, arXiv, government sites, and any PDF you view in Chrome.
Yes. CastReader is a free online PDF to MP3 converter — upload your PDF, it extracts the text, converts it to natural AI speech, and lets you download each chapter as an MP3 file. No signup, no watermark, no daily limit. Most PDFs convert in under 30 seconds. Works with multi-column layouts, textbooks, and scanned documents.
If you can open and view the PDF (i.e., you know the password), the text extraction will work after you unlock it. Fully encrypted PDFs that you cannot open are not supported — you need access to the content for any converter to work.
PDF not converting correctly? Send it to our debug team
Read any PDF aloud directly in Chrome — no download needed
Convert EPUB, DOCX, and other documents to audio
Convert any text to natural AI speech — no signup, no limits
70,000+ public domain books you can listen to for free
The only TTS that works on Kindle Cloud Reader
How dual-channel reading helps — tools and techniques
硬数据 —— 不是 vibe —— 来自权威来源
effect size 0.35
22 篇研究的 meta 分析显示 TTS 对阅读障碍学生的理解力提升幅度（Wood, Moxley, Tighe & Wagner, Journal of Learning Disabilities, 2018）
Source →下方每一条 Chrome Web Store 评论都可以在卡片链接处验证。我们不藏负面反馈 —— 我们 24 小时内回复。
“This is 1 of the best TTS and its smooth. If this is truly free i'll keep this 100%. Every other TTS says its free but has a secret. They interrupt or they just say better ai voices pay. But i like this voice. I've tried loads and this is 1 of the best ones that actually says free.”
“Works perfectly on vivaldi. One suggestion though. I wish it had a play button appear next to a paragraph when we hover over it. Just like in the case of speechify.”
“Extremely user friendly short keys. Placed forward backward and speed up down as Natural as it could be. Voices are great and smooth. I would recommend it over many hyped products.”
“At the very least it's better than many paid TTS models. Still not as good as ElevenReader or LAP, but maybe the best free model for TTS.”
“So glad I can finally switch voices! The default was fine but I found one I actually enjoy listening to for hours. Small thing, huge difference.”
“Best one i found, user friendly, and great voice over.”
“ChatGPT's long answers are finally listenable. Let it generate while I listen — doubles my productivity. Love the inline button next to each response.”
“I tried using this add-on to listen to an ebook on the O'Reilly learning platform, and it works smoothly. However, it always restarts from the first paragraph whenever I scroll or select a different paragraph. Please consider adding a bookmark or checkpoint feature so users can mark where the reading should begin.”
↪ Founder reply
CastReader 创始人 Yan Xu 48 小时内回复：承认问题，下个版本上线了 bookmark 功能。这条评论的反馈直接推动了 v1.2 路线图。
“Need to highlight text and select it.”
“Hard to select text.”
↪ Founder reply
CastReader 创始人 Yan Xu 24 小时内回复：道歉、询问发生的网站/浏览器、提供键盘快捷键作为绕过方案、留下 support@castreader.ai 直接支持邮箱。
我们持续测试、改写、上线。每条更新都带真实日期。
用 verbatim Chrome Web Store testimonial、真实有声书市场数据、12 工具实测的 methodology 重写落地页。每条主张都有来源链接。
Telegram 音频流现在能稳定自动翻页，覆盖 Kindle Cloud Reader 和 Apple Books。内部测试显示会话中断减少约 70%。
写了 OCR 管线的深度文章：CastReader 如何处理 Amazon 每本 Kindle 书 184 套随机字母表和 361 个独特 glyph。发表在 dev.to。
原生 macOS 应用，朗读 Kindle for Mac，词级高亮。浮窗播放器 + 系统级快捷键。不需要浏览器。
Daily 榜 #10，99 upvotes，4 条社区评论推动了 v1.2 路线图。
从旧 TTS 引擎切换到 Kokoro 神经网络语音。用户评论从 'usable but robotic' 转为 'enjoy listening for hours'（来自 patrick chiang 的 Chrome Web Store 评论原话）。
英文 Kindle 书的 OCR 成功率从 78% 提升到 89%。加入了多栏页面检测（学术 PDF 适用）。
我做 CastReader 是因为我有几百本 Kindle 书，想在晨跑时听它们，但不想为每本再买 Audible 版。技术问题 —— Amazon Cloud Reader 的字体加密 —— 最后用 OCR 解决了。产品问题 —— 让它在手机、桌面、40+ 语言上真正好用 —— 花了两年迭代。我们是个小团队。我亲自回复每一条 Chrome Web Store 评论（上方 testimonials 里有证明 —— 包括 3 星和 1 星的）。如果有什么坏了或缺失，邮件 support@castreader.ai。
—— Yan Xu, 创始人
最近审阅: · CastReader 团队 —— 基于 2025 测试数据
Free CastReader works on Chrome / Edge / iOS / Android / Mac. Read any PDF aloud, on any platform.
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