How to use an AI assistant in your browser on any page

By the end of this guide you will have an AI browser assistant installed, you will know how to call it on any page to summarize, question or rewrite what you are reading, and you will have set sensible limits on what it can see and do. The job is done by an AI browser extension that sits in a sidebar or opens from a shortcut and reads the page you are on.

An AI browser extension assistant comes in three main forms: multi-model chat that understands the current page, single-purpose summarizers, and agents that act on websites for you. This guide explains how to choose and compares six options from our Chat assistants category.

Key takeaways

• Install one extension, pin it, open a page and ask about it, then check the answer against the page before you rely on it.
• The main decision is the type: a multi-model assistant, a free summarizer for pages, PDFs and videos, or an agent that clicks and types on your behalf.
• Free plans are capped: HARPA AI's Demo plan allows 10 messages a day on web session connections and 100 AI command runs in total, and Monica's Free plan gives 40 basic queries a day.
• Extensions can read what is on your screen. Keep them off banking, health and confidential pages, and review what an agent is allowed to do.

What you need before you start

• A supported browser. Most tools here are Chrome extensions, and Composite also lists Edge, Brave and Arc.
• An account. Most tools here have a free plan or free use, and SummaryTube says signing in with Google is enough to start.
• A page to test on. An article, a YouTube video or a PDF you are reading anyway.
• Time. Installing and a first test take under half an hour.
• Difficulty. Easy for chat and summarizing, moderate for agents and scheduled commands.
• A rule for sensitive pages. Decide now which sites you will never open with an extension active.

Which kind of AI tool fits this job

Pick by the kind of help you want on a page.

Multi-model assistants that read the page. HARPA AI sits on top of any web page and lets you call models from several providers from one shortcut. It can summarize articles, PDFs and YouTube videos, draft email replies and monitor pages for changes. Merlin is a Chrome extension and web app that lets you chat with models from several providers and ask about the page you are reading without switching tabs. Monica works as a browser extension with a sidebar and toolbar, and also has a web app, desktop apps and mobile apps.

Focused summarizers. Gist AI is a Chrome extension that gives short summaries of websites, YouTube videos and PDFs, and describes itself as completely free. SummaryTube summarizes YouTube videos with key moments, timestamps and a transcript, and lets you ask questions about the video.

Agents that act on websites. Composite is an AI browser agent: you press a shortcut, describe a task in plain English, and it clicks, types and moves between pages using your existing logged-in sessions. It is powerful, so it needs more care than a summarizer.

Step 1: Decide what you want help with

You end this step with a short list of jobs, which tells you which kind of tool to install.

1. List the tasks you repeat most, such as summarizing articles, answering questions about a PDF, drafting replies or filling forms.
2. Separate reading help (summaries and questions) from action help (clicking and typing).
3. Note which sites you use most, for example YouTube, Gmail or LinkedIn.
4. Decide your budget, and whether free limits will do.

Check it worked by having a list of two or three jobs you would hand over.

Step 2: Pick an extension and install it

Install one extension first, not several.

1. For multi-model chat on any page, start with HARPA AI, Merlin or Monica.
2. For quick summaries only, try Gist AI or, for YouTube alone, SummaryTube.
3. For tasks that need clicks, consider Composite after you have used a simpler tool.
4. Install from the browser's extension store, and pin the icon to the toolbar so it is easy to open.

Check it worked by seeing the extension's icon in the toolbar and opening its panel.

Step 3: Sign in and set your preferences

A few minutes of setup avoids surprises later.

1. Create an account or sign in. Signing in with Google is enough to start with SummaryTube.
2. Choose a default model or provider if the tool lets you. HARPA AI can use your own API keys or web sessions from ChatGPT, Claude and Gemini.
3. Look at the privacy and data settings, and read what the vendor says it stores.
4. Set a keyboard shortcut for opening the assistant, where one is offered.

Check it worked by opening the assistant on a blank tab and sending a harmless test message.

Step 4: Try it on a page you are reading

Start with something low-stakes.

1. Open an article, then ask the assistant to summarize it and list the three main points.
2. Ask a specific question about the page, such as "what does the author say about costs?".
3. Try a PDF or YouTube video. Gist AI works from the toolbar icon on websites, videos and online PDFs, and uploads local PDFs through its PDF tab. For video it pulls the transcript before summarizing.
4. Use features that point back to the source. Gist AI has a Read More link to the passage behind each point, and SummaryTube gives timestamps.

Check it worked by comparing the summary with the page and finding the key points present and accurate.

Step 5: Use it for writing and replies

Once reading help works, add drafting.

1. Select the text you want to rewrite, or open an email thread, and ask for a draft reply in your tone.
2. Merlin lists an email and reply composer for Gmail, LinkedIn and X, and HARPA AI has a Gmail assistant that drafts replies.
3. Read every draft and edit it before sending. Names, dates and promises need your own check.
4. Save the prompts that work as commands or templates if the tool supports it. HARPA AI has over 100 ready-made commands and lets you build your own.

Check it worked by sending one reply that you edited and that still sounds like you.

Step 6: Add monitoring or automation carefully

Agents and scheduled tasks save time but carry more risk.

1. Start with read-only automation, such as page monitors. HARPA AI can watch a page for price drops or items back in stock.
2. For action agents, begin with a harmless task on a site you trust. Composite works through your own browser and logged-in sessions, so it can reach anything you can sign in to.
3. Watch the first runs, and stop the agent if it does something unexpected.
4. Never let an agent make payments, send messages or change account settings without you reviewing the step.

Check it worked by completing one small automated task and confirming exactly what it did.

Step 7: Keep your data and costs under control

Extensions can see a lot, so set boundaries.

1. Turn the extension off, or use a separate browser profile, for banking, health, work-confidential and personal-account pages.
2. Review the permissions the extension has, and remove extensions you stopped using.
3. Watch usage limits. Monica meters usage through queries and advanced credits, and HARPA AI's free plan has a total cap.
4. Revisit your tools every few months, since features and plans change.

Check it worked by being able to list which sites each extension can access.

Tools for this job compared

Tool	Good fit for	Pricing	Stated limits
HARPA AI	Page-aware chat, summaries, monitors and scraping, as a Chrome extension	Freemium, paid from €14.3/mo (checked 24 Oct 2026)	Free Demo: 10 messages a day on web sessions and 100 AI command runs in total; no trial period; lifetime plan allows one active device
Merlin	Multi-model chat about the page, plus email and reply drafting	Paid	Details shown come from the Teams page; quoted per-seat figures differ between $19 and $15; extreme usage could lead to restrictions
Monica	Multi-model chat with sidebar, ChatPDF and agent features	Freemium	Free plan has 40 basic queries a day and no advanced queries; agent tasks and images use advanced credits
Gist AI	Free one-click summaries of websites, videos and PDFs	Free	Chrome only; summaries come from ChatGPT and can miss nuance; YouTube summaries rely on the transcript
SummaryTube	YouTube summaries with timestamps and a transcript	Freemium, paid from $2/mo (checked 24 Oct 2026)	Free plan has a limited number of summaries per month; YouTube videos only
Composite	An agent that does tasks in your browser	Freemium, paid from $20/mo (checked 24 Oct 2026)	Free plan has a lower monthly AI request allowance than Pro; you must be signed in to the sites it acts on

Prices and plan limits change, so confirm the current terms on each vendor's site before you subscribe.

Common mistakes to avoid

• Trusting a summary without checking. Summaries can miss nuance. Gist AI's listing notes that its ChatGPT-written summaries can miss nuance, so check the source for key details. Open the passage the summary points to.
• Leaving extensions on for sensitive pages. An assistant that reads the page can read private content too. Switch it off or use another browser profile for banking, health and confidential work.
• Giving an agent too much freedom. Composite acts through your signed-in sessions, so a mistake can happen in a real account. Start with low-risk tasks and watch the first runs.
• Installing several assistants at once. Overlapping shortcuts and permissions get confusing. Try one, learn it, and add another only if it fills a gap.
• Ignoring free limits. Caps like HARPA AI's 100 total command runs on the Demo plan run out quickly. Check the limits so you are not surprised mid-task.

How we put this together

This is an evidence-based guide built from each tool's listing in our directory, which is compiled from the vendor's own site and pricing page. It is not a review based on using the tools. We don't rank tools, and nobody paid to be included. Some outbound links may be affiliate links; see our disclosure.

Frequently asked questions

Is there a free AI assistant for my browser?

Yes. Gist AI describes itself as completely free with no limit on content length, and HARPA AI, Monica, SummaryTube and Composite all have free plans with limits. Free plans cap messages, queries or summaries, so check them against how often you will use the tool.

Can an AI browser assistant read PDFs and YouTube videos?

Several can. HARPA AI summarizes articles, PDFs and YouTube videos, Gist AI handles websites, YouTube and PDFs, and Monica includes ChatPDF. SummaryTube works with YouTube videos only. Gist AI's YouTube summaries rely on the video's transcript.

Is it safe to use an AI extension on every page?

Not necessarily. An extension that reads the page can see whatever is on it, so avoid using one on banking, health or confidential pages. Read each vendor's data terms, and review the permissions the extension asks for.

Which tool works on a phone?

Monica lists mobile apps for Android and iOS as well as desktop apps, so it is the one in this list with a phone option. The others are described as Chrome extensions or web apps. Check each vendor's site for current mobile support.

Can an AI agent fill in forms and click through sites?

Composite can: you describe a task in plain English and it clicks, types and moves between pages using your existing logins. Keep a close eye on it, and do not let it handle payments or account changes without checking each step.

Compare more options in our Chat assistants category.