Because in May 2021 Google migrated Google Docs from a contenteditable DIV to a Canvas-based renderer. Chrome's Read Aloud — like every other DOM-based TTS — walks the HTML looking for text, and on a Canvas page there's nothing to walk. CastReader hooks the Docs document model instead, so it works regardless of how the page is painted.
Partially. Speechify can read the first screen (via the accessibility tree) and then stops when it hits the virtualized Canvas region. If your document is longer than ~20 lines, Speechify will read the beginning and go silent. This is a known limitation open in their forums since 2022.
Yes. As long as Google Docs lets you open the document in your browser (any role — editor, commenter, viewer), CastReader reads it aloud. No special permission required.
Yes. CastReader attaches to the Docs model regardless of theme or container. It works in standalone docs.google.com, in Google Classroom embeds, and in Google Workspace (formerly G Suite) deployments.
Google Sheets and Slides use different document models. CastReader currently ships with Docs support. Slides support is on the roadmap. Sheets is less likely — spreadsheet cell-by-cell reading is a different UX problem.
The main document body is read aloud. Comment threads and suggestion mode tracked changes are skipped to keep the narration clean — if you want them, leave a feature-request GitHub issue.
40+ natural AI voices across English, Spanish, French, German, Japanese, Chinese, and more. The language is auto-detected from the document content — mixed-language docs use the dominant language.
Start playback in Chrome, then click 'Send to Phone'. Audio streams to your phone via Telegram — no mobile app needed, no sync setup.
CastReader is free to use, no account required, with natural AI voices. No trial period to worry about. CastReader Pro (optional) adds premium ultra-realistic voices, more listening hours, voice cloning, and AI document analysis — unlike Speechify's $139/year or NaturalReader's paywall tiers.
The full Google Docs support page with setup details
Encrypted font glyphs break every TTS tool — here's the fix
PDFs that Chrome, Speechify, NaturalReader can't read
Canvas-rendered Chinese e-books, read aloud in browser
Download the CastReader app to listen to your uploaded documents anywhere.
Hard numbers — not vibes — from authoritative sources
$2.22 billion
US audiobook sales in 2024, up 13% year-over-year (Publishers Weekly / Audio Publishers Association)
Source →51%
of US adults have listened to an audiobook in 2025 — roughly 134 million people (APA Consumer Survey 2025)
Source →2.2 billion
people globally with near- or far-vision impairment (WHO Fact Sheet, 2024). TTS is the primary access path for digital reading content.
Source →78%
of audiobook listeners multitask while listening — commute, chores, exercise (Audiolibrix Great Audiobook Survey, 2024)
Source →27.2 minutes
average single-trip US commute in 2024, up from 26.8 (US Census ACS via Statista). That's nearly an hour each day of audio-only time.
Source →effect size 0.35
measured comprehension lift from TTS for reading-disabled students across 22 studies (Wood, Moxley, Tighe & Wagner, Journal of Learning Disabilities, 2018)
Source →15.5 million
US adults with ADHD per CDC 2024 — about half diagnosed in adulthood (CDC MMWR, October 2024)
Source →Every Chrome Web Store review below is verifiable at the link in each card. We don't hide negative feedback — we answer it within 24 hours.
“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
Replied by CastReader founder Yan Xu within 48 hours: acknowledged the issue, shipped a bookmark feature in the following release. Reviewer's verbatim feedback drove the v1.2 roadmap.
“Need to highlight text and select it.”
“Hard to select text.”
↪ Founder reply
Replied by CastReader founder Yan Xu within 24 hours: apologized, asked which site/browser the issue occurred on, provided a workaround using the keyboard shortcut, and offered direct support at support@castreader.ai.
We re-test, re-write, and ship continuously. Every entry has a real date.
Rewrote landing pages with verbatim Chrome Web Store testimonials, real audiobook market data, and tested-12-extensions methodology. Every claim now has a sourceable link.
Telegram audio streaming now auto-turns pages reliably across Kindle Cloud Reader and Apple Books. Reduces session interruptions by ~70% in internal testing.
Wrote up the OCR pipeline: how CastReader handles Amazon's 184 random font alphabets and 361 unique glyphs per Kindle book. Shared in dev.to.
Native macOS app reads Kindle for Mac with word-level highlighting. Floating player + system-wide hotkeys. No browser needed.
Ranked #10 in Daily, 99 upvotes, 4 community comments shaped the v1.2 roadmap.
Switched from older TTS engines to Kokoro neural voices. User reviews shifted from 'usable but robotic' to 'enjoy listening for hours' (verbatim from review by patrick chiang).
OCR success rate improved from 78% to 89% on English-language Kindle books. Multi-column page detection added for academic PDFs.
I built CastReader because I owned hundreds of Kindle books and couldn't listen to them on my morning runs without buying separate Audible copies. The technical problem — Amazon's Cloud Reader font encryption — turned out to be solvable with OCR. The product problem — making it actually pleasant across phones, desktops, and 40+ languages — took two years of iteration. We're a small team. I answer every Chrome Web Store review personally (see testimonials above — including the 3-star and 1-star ones). If something's broken or missing, email support@castreader.ai.
— Yan Xu, founder
Last reviewed: · CastReader Team — reviewed against 2025 testing data
Install once. Open any Google Doc. Click ▶. Listen.
★★★★★ 4.7 · Free to start · No login · Optional Pro