
SpecialistOpenAI's flagship multimodal assistant powered by GPT-6 and GPT-5.6 for reasoning, coding, and deep research.

CastReader records 55,999 monthly visits with +9.8% month-over-month growth and Freemium pricing. Sider records 2,644,740 monthly visits with -10.6% growth and Freemium pricing.

Read aloud webpages, PDFs, Kindle books and AI answers with synced highlighting
| Dimension / Metric | ![]() | |
|---|---|---|
| Official Domain | castreader.com | sider.ai |
| Pricing Model | Freemium | Freemium |
| Monthly Visits | 56K (55,999) | 2.64M (2,644,740) |
| MoM Traffic Delta | +4.98K (+9.8%) |
| -314.2K (-10.6%) |
| Primary Market & Share | 🇺🇸 United States (56%) | 🇺🇸 United States (13.3%) |
|---|
| Direct Visits / mo | 19.7K | 1.7M |
|---|
| User Rating | 4.4 | 4.5 |
|---|
| Supported Platforms | Website | Website |
|---|

Read aloud webpages, PDFs, Kindle books and AI answers with synced highlighting
Natural AI voices narrate webpages, PDFs, ebooks and documents while each spoken word is highlighted and the page auto-scrolls, so you never lose your place.
Instead of only reading a hard passage, CastReader summarises and unpacks its meaning in the language you know best, with an animated pen marking the key lines in the original text.
Works across Kindle, WeRead, Google Play Books, O'Reilly and other book platforms, news and newsletter sites, Google Docs, Notion, Gmail, plus ChatGPT, Claude, Gemini, DeepSeek and Kimi answers.
Preview real samples of dozens of voices across many languages, and create private cloned voices that Pro members can apply to their own PDF, EPUB, Word and TXT files.
AI sidebar and browser agent for reading, writing and research
A persistent panel that reads the page you are on and answers follow-ups with GPT, Claude or Gemini without copying content into another tab.
Summarise long articles, PDFs and YouTube videos, extract key points, and ask detailed questions about the source material.
Translate webpages, PDFs and images, compare bilingual output side by side, and have content read aloud for review on the move.
Delegate multi-step tasks across real websites — price comparison, form filling, research and inbox triage — using your existing logged-in sessions.

SpecialistOpenAI's flagship multimodal assistant powered by GPT-6 and GPT-5.6 for reasoning, coding, and deep research.

SpecialistAnthropic's frontier AI workspace powered by Claude 5.5 for agentic coding, analysis, and nuanced writing.
Text to speech and voice AI across every device

Offers a very similar browser sidebar experience with multiple AI models, but features slightly different pricing and workspace tools.
Free AI text to speech with 200+ voices in 70+ languages
Provides robust browser-based summarization and prompt assistance, but lacks some of Sider's deeply integrated multi-model chat UI features.
Excels at advanced web automation and data extraction alongside chat, but has a steeper learning curve than Sider.
Listen to anything. Beautifully.

Free / Open-sourceSummarize YouTube, Google, and any page with AI — free in your browser
Integrates bookmark management and content composition into a clean sidebar, but has a more limited feature set than Sider.
Delivers streamlined inline writing and webpage summarization via a browser extension, but with fewer custom sidebar tools.

Turn any webpage, PDF, Doc or ebook into natural-sounding speech in 60+ languages
SpecialistOpenAI's flagship multimodal assistant powered by GPT-6 and GPT-5.6 for reasoning, coding, and deep research.
SpecialistAnthropic's frontier AI workspace powered by Claude 5.5 for agentic coding, analysis, and nuanced writing.
Text to speech and voice AI across every device
Offers a very similar browser sidebar experience with multiple AI models, but features slightly different pricing and workspace tools.
Free AI text to speech with 200+ voices in 70+ languages
Provides robust browser-based summarization and prompt assistance, but lacks some of Sider's deeply integrated multi-model chat UI features.
Listen to anything. Beautifully.
Free / Open-sourceSummarize YouTube, Google, and any page with AI — free in your browser
Integrates bookmark management and content composition into a clean sidebar, but has a more limited feature set than Sider.
Delivers streamlined inline writing and webpage summarization via a browser extension, but with fewer custom sidebar tools.
Turn any webpage, PDF, Doc or ebook into natural-sounding speech in 60+ languages