A growing number of people want an AI assistant pinned to every webpage they read, not a separate chatbot tab they keep reopening. The tools in this guide live inside the browser — or next to it — so you can summarize an article, rewrite a paragraph, translate a sentence, or cross-check an answer without leaving the page. We compared five of the most capable options on model access, pricing, privacy posture, and how they fit real daily workflows.

Quick picks at a glance

How we evaluate

We did not run a timed benchmark with fixed sample sizes. Instead, we assess each product on the dimensions that matter for everyday browser use: how many frontier models it puts within reach, how readable its pricing is, whether your data stays local or leaves the machine, and how naturally it fits a reading-writing-research workflow. Ratings in this post are taken directly from each tool’s directory profile, and the prices below reflect the plans listed at the time of writing. Where a vendor gates the best models behind paid tiers, we say so plainly.

1. Monica — best for an all-in-one sidebar

Monica aggregates GPT-5, Claude, Gemini, and DeepSeek behind one lightweight sidebar you summon on any page with a shortcut. For a knowledge worker who wants one subscription to replace a rotating cast of single-purpose apps, it is the most convenient option we reviewed: it summarizes the page you are reading, rewrites selected text, drafts email replies, and chats with uploaded PDFs. A built-in math solver shows step-by-step workings, and a “humanizer” rewrites AI text to read more naturally.

• Pros: Accesses GPT-5, Claude, Gemini, and DeepSeek in a single sidebar; strong free tier across Chrome, Edge, desktop, and mobile; built-in ChatPDF, webpage summarizer, and 80+ writing templates.
• Cons: Free plan daily limits are very restrictive; the credit ladder and pricing tiers feel confusing; advanced models sit heavily behind paid plans.
• Price: Free ($0/mo, 40 daily basic accesses); Pro $8.3/mo (billed $99/yr); Unlimited $16.6/mo (billed $199/yr).
• Skip it if: You only need one model and hate learning a credit system — a single-purpose chatbot like ChatGPT may be simpler.
• → Full profile: Monica

2. Sider — best for comparing many models at once

Sider docks a sidebar onto every webpage with more than 20 models — GPT-4o, Claude, Gemini, DeepSeek, Grok, and others — so you never open a separate app to explain, translate, or rewrite text. Its Group Chat mode sends one prompt to several models simultaneously and shows their answers side by side, which is genuinely useful for weighing perspectives or fact-checking. With over 10 million users, it is the consolidation play for people who would otherwise maintain several chatbot subscriptions.

• Pros: 20+ models in one sidebar with no separate subscriptions; a genuine free tier (30 daily basic credits) to evaluate first; strong reading helpers for webpages, YouTube, and PDFs.
• Cons: The credit system is confusing and premium models drain credits fast; chat history disappears when you close the tab; no native Firefox extension or local-first privacy option.
• Price: Free ($0, 30 basic credits/day); Basic $8.30/mo; Pro $16.60/mo; Unlimited $25/mo.
• Skip it if: You need persistent, searchable chat history or Firefox support — a dedicated assistant such as Claude keeps longer threads.
• → Full profile: Sider

3. Cuey — best for a cross-model sanity check

Cuey is a Chrome extension that sits inside your existing ChatGPT, Claude, or Gemini session and routes the same prompt across 20+ models at once, so you can compare outputs before committing to an answer. For judgment-heavy work — research, advice, code explanations — that cross-model check surfaces a factual gap one model missed. A portable memory layer keeps your prompts and context consistent as you move between providers, and the free tier has no model paywalls.

• Pros: Runs one prompt across 20+ models in a single side-by-side view; portable memory and prompt workflows travel across AI services; a permanent free tier with no model paywalls.
• Cons: The free tier caps comparisons (15 per week on the verified plan); no public API for piping comparisons into pipelines; one-shot comparison only, no iterative multi-step verification.
• Price: Free forever ($0, 15 comparisons/week); Pro $9.99/mo (100/week, 500MB storage, long-context modes); Enterprise custom.
• Skip it if: You need programmatic, API-driven verification inside an agent pipeline — a search layer such as Perplexity or a coded workflow fits better.
• → Full profile: Cuey

4. Dia — best for research across open tabs

Dia is a full AI-native Chromium browser from the team behind Arc. Instead of bolting a chatbot to the side, it weaves a frontier-LLM assistant into the core: the URL bar doubles as a prompt, and the assistant reads the page you are on and reasons across every open tab at once. You can ask it to compare products spread across tabs, draft a reply in Gmail, or find something you read last week. Because it is a complete browser, your existing Chrome extensions keep working.

• Pros: Page-aware AI in every tab removes the copy-paste dance to a chatbot; multi-tab reasoning compares products and synthesizes sources automatically; full Chromium base keeps your Chrome extensions working.
• Cons: macOS Apple Silicon only, with no Windows or mobile client yet; no autonomous agent mode or API; the free tier AI message cap is low for heavy users.
• Price: Free ($0, ~50 AI messages/day); Pro $20/mo (unlimited chat, full Skills, 7-day history).
• Skip it if: You are locked to Windows or need an API — Monica or Sider run on the browser you already use.
• → Full profile: Dia

5. Raycast — best for Mac users who want a keyboard-first copilot

Raycast is an AI-powered launcher and command palette for Mac that unifies search, snippets, window management, and multi-model chat behind one keyboard shortcut. It is not a browser extension, but for Mac users it serves the same “AI always one keypress away” role without leaving whatever app you are in. Thousands of community extensions and Cloud Sync make it a hub for notes, snippets, and quick AI drafts, with Raycast AI bundling many top LLM providers in one chat.

• Pros: A blazing-fast launcher with thousands of community extensions; Raycast AI bundles many top LLM providers in one chat; Cloud Sync keeps snippets, notes, and chats across devices.
• Cons: Mac-only (Windows is still in limited beta); meaningful AI requires the Pro plan; the model lineup trails dedicated browser copilots for in-page reading.
• Price: Free ($0, 50 AI messages, limited notes); Pro $8/mo; Pro + Advanced AI $16/mo; Teams Pro $12/user/mo.
• Skip it if: You are on Windows or want AI anchored to the webpage you are reading — a browser sidebar like Sider fits better.
• → Full profile: Raycast

How to choose

• Everyday knowledge worker on any OS → Monica for the broadest all-in-one sidebar.
• Researcher who distrusts single answers → Cuey for the side-by-side model check.
• People who compare products and read across tabs → Dia if you are on a Mac and ready to switch browsers.
• Mac power user living in the keyboard → Raycast for launcher-plus-AI.
• Casual user who just wants multi-model chat → Sider with its fair free tier.

Related tools & guides

• ChatGPT — the standalone chatbot many of these copilots wrap.
• Claude — a leading model you can reach inside Monica, Sider, and Cuey.
• Perplexity — an answer engine for grounded, cited lookups.
• Fathom — an AI meeting notetaker if your copilot work extends to calls.
• Best AI Productivity Tools 2026 — broader roundup of daily-driver AI apps.
• ChatGPT vs Claude 2026 — how the two models behind most sidebars compare.
• Best AI Meeting Assistants 2026 — capture and summarize the calls your copilot cannot join.