How do their growth rates compare?

ChatPDF has a month-over-month growth rate of -3.7%; Thinkstack.ai has -47.4%.

How does pricing compare?

ChatPDF: Freemium. Freemium. A free tier lets you analyze a limited number of documents per day, and the core chat experience works without creating an account. ChatPDF Plus is a paid subscription that adds unlimited document analysis and advanced features — check the site for current plan details and regional pricing. Thinkstack.ai: Freemium. Freemium with a free starting plan and paid tiers for higher usage and features; enterprise pricing is available on request. See the pricing page for current details.

What are alternatives to ChatPDF and Thinkstack.ai?

Other tools in related categories include Claude, PDFgear, LightPDF, UPDF AI, Tidio.

ChatPDF vs Thinkstack.ai — Traffic (1.04M vs 917), Pricing & Verdict

Open AI Tools

ChatPDF vs Thinkstack.ai — Traffic (1.04M vs 917), Pricing & Verdict | Open AI Tools

Side-by-Side Traffic & Specification Matrix

Dimension / Metric	ChatPDF	Thinkstack.ai
Official Domain	chatpdf.com	app.thinkstack.ai
Pricing Model	Freemium	Freemium
Monthly Visits	1.04M (1,044,477)	917 (917)
MoM Traffic Delta	-40.47K (-3.7%)	-828 (-47.4%)
Primary Market & Share	🇺🇸 United States (9.6%)	🇺🇸 United States (48.2%)
Direct Visits / mo	457.79K	367
User Rating	4.2	4.1
Supported Platforms	Website	Website

ChatPDF

Chat with any PDF, video, or website and get cited answers in seconds

Cited answers

Every response is anchored to your source document with clickable citations that scroll to the exact passage, so verification takes seconds instead of page-by-page searching.

Multi-file chat and folders

Organize documents into folders and query many files in a single conversation to compare arguments, cross-reference findings, or study a whole syllabus at once.

Summarization and translation

Condense long papers, reports, and contracts into key takeaways, and translate or query documents in any language — including mixing a source language with a different question language.

Study and writing tools

Generate flashcards and slide decks from your material, and use the built-in AI writer and AI detector for drafting and checking academic text.

Strengths & Pros

+Answers include clickable citations tied to the original page, which makes fact-checking straightforward
+Works with PDFs, Word, PowerPoint, Markdown, text, YouTube links, and web pages in one place
+No account needed to try the core chat experience, and the free tier covers light daily use
+Multilingual: upload in one language and ask questions in another