Side Reader

Side Reader positions itself as a pragmatic bridge between dedicated PDF analysis tools and the increasingly versatile AI chat interfaces millions use daily. Rather than building a standalone platform, this Chrome extension injects PDF reading and chat capabilities directly into the sidebars of ChatGPT, Claude, and DeepSeek. The core thesis is simple: if you already live inside these AI environments for research, drafting, or analysis, Side Reader eliminates the friction of switching tabs or copying text back and forth. It turns each AI chat into a document workspace, offering summarization, translation, and explanation on any uploaded PDF. For users who regularly toggle between multiple AI platforms, the extension's cross-platform compatibility is its strongest differentiator — you get a consistent reading experience whether you prefer OpenAI's models, Anthropic's Claude, or DeepSeek's growing ecosystem.

Where Side Reader truly stands out is in its workflow integration. Instead of forcing you to adopt a new tool with its own interface and learning curve, it layers onto existing habits. A researcher can upload a 20-page paper into ChatGPT, ask for an executive summary, then drill into specific sections — all without leaving the chat window. A lawyer handling a French contract can open it inside Claude, request a translation, and then ask clarifying questions about specific clauses. A technician can drop a complex equipment manual into DeepSeek and get step-by-step explanations of troubleshooting procedures while viewing the original diagrams in a split-screen layout. The adjustable split-screen width and PDF zoom are small but meaningful touches that improve readability over default AI interfaces, which were never designed for document-heavy work.

However, the free tier's limitations are severe enough to demand careful consideration. With a daily upload cap of just three PDFs and a 10MB file size limit, heavy users will hit constraints quickly. The free version also keeps only the last three uploads in history, making multi-session research workflows impractical. For students or casual users who need occasional explanations of textbook excerpts, the free tier may suffice if they plan uploads strategically. But for professionals — researchers, lawyers, technical writers — the Pro tier at $9.80 per user per month becomes almost necessary, lifting limits to 50 PDFs per day, 50MB per file, and 100 records of upload history. The Pro-exclusive Capture & Ask feature, which lets users select a portion of the PDF and query the AI about it, adds significant value for power users who need to interrogate specific charts, paragraphs, or data tables.

Side Reader's narrow platform dependency is both a strength and a limitation. It only works on the websites of ChatGPT, Claude, and DeepSeek, and only as a Chrome extension — no mobile app, no Firefox or Safari support, no offline functionality. This means users who rely on desktop apps or other browsers are excluded. Additionally, the extension does not store documents or process AI requests itself; it simply facilitates the connection between the PDF and the AI platform. All data handling falls under the respective AI provider's privacy policy, which is worth noting for anyone dealing with sensitive legal, medical, or proprietary documents. The company behind Side Reader appears small, with limited public information and a support channel through a Feishu form, which may raise concerns about long-term viability or responsiveness for enterprise users.

For practical buyers and operators, Side Reader is best evaluated as a productivity enhancer rather than a standalone solution. The decision hinges on three factors: how many AI platforms you actively use, how many PDFs you process daily, and whether the free tier's restrictions align with your actual volume. A researcher who mainly uses ChatGPT and handles fewer than three papers a day may never need to upgrade. A lawyer juggling multiple contracts across Claude and DeepSeek will almost certainly hit the free limits and should budget for Pro. The extension's real value emerges when you are already committed to these AI ecosystems and want a seamless document layer — it is not a replacement for dedicated PDF tools like PDFAI or ChatPDF, but it may be more convenient if you prefer staying inside your existing chat environment. Side Reader earns its place as a thoughtful, if narrowly scoped, tool for a specific kind of user: the AI-native knowledge worker who wants their documents to live where their conversations happen.