Microsoft’s Copilot redesign this month put Home, Code, and Autopilot into a permanent browser sidebar. That is the shape most people now expect: an AI window pinned next to your tabs, aware of the page you are reading, able to summarise, translate, or answer questions without a copy-paste dance. You do not need to use Edge or Copilot to get this. Seven desktop apps put the same always-on sidebar into Chrome, Firefox, Safari, or Arc, some with the option to run against local models. We tested each on a mix of research, shopping, and coding tabs.
What to look for in a browser sidebar AI
- Page-aware context. The assistant should read the current page without you pasting URLs.
- Multi-model choice. Being stuck on one model (Copilot only, GPT only) ages badly. Pick tools that let you switch.
- Local model support. For sensitive tabs, being able to route the query to Ollama saves you leaks.
- Selection quick actions. Highlight text on any page, get a translation or explanation with one click.
- Cross-tab reasoning. The best assistants can compare or summarise across multiple open tabs.
- Keyboard shortcut discipline. A sidebar you never open is dead weight. Good shortcuts keep it in the workflow.
Quick comparison
| App | Best for | Free plan | Platforms | Bring your own model |
|---|---|---|---|---|
| Sider | Multi-model shopping and research | Yes (freemium) | Windows, macOS, Linux (Chrome extension) | Yes |
| Perplexity Comet | Research-first browsing | Yes | Windows, macOS | No, hosted only |
| Arc Max | Native browser AI | Yes (freemium) | macOS, Windows | Limited |
| SigmaOS | Workspace-oriented AI | Yes (freemium) | macOS | Limited |
| Page Assist | Fully local sidebar for Ollama | Yes (open source) | Windows, macOS, Linux | Yes, Ollama |
| Monica | Sidebar with app-store style plugins | Yes | Windows, macOS, Linux | Yes |
| Merlin | GPT-4 quota-friendly sidebar | Yes | Windows, macOS, Linux | Yes |
| Brave Leo | Built-in Brave browser AI | Yes | Windows, macOS, Linux | Yes, Ollama |
The 8 best browser sidebar AI assistants
1. Sider, most flexible multi-model sidebar
Sider installs as a Chrome or Edge extension and adds a sidebar that lets you talk to GPT-4o, Claude Sonnet, Gemini, or your own Ollama endpoint from the same window. Page-aware summarise, translate, and ask actions cover 80% of daily use. The recent update added a “compare tabs” mode that pulls the primary content from every open tab and cross-summarises.
Where it falls short: Free tier quota is modest. Some premium models are only in the paid tier.
Pricing:
- Free: Limited quota, most models available
- Paid: Sider Pro around $10 per month
Platforms: Windows, macOS, Linux (Chrome, Edge, Brave, Firefox)
Download: Sider.ai
Bottom line: The default recommendation for most people. Skip if you want a browser-native experience rather than an extension.
2. Perplexity Comet, research-first browsing
Comet is Perplexity’s native browser (Chromium-based). Instead of a sidebar bolted onto your current browser, Comet builds the sidebar into every tab as a first-class citizen. Answers are grounded in web sources with citations, and follow-ups stay in the same tab as the page you were reading. The “agentic” mode can navigate a booking flow or checkout page on your behalf.
Where it falls short: You have to adopt a new browser. Extension ecosystem is smaller than Chrome or Firefox.
Pricing:
- Free: Limited access
- Paid: Perplexity Pro around $20 per month unlocks agentic actions
Platforms: Windows, macOS
Download: Comet by Perplexity
Bottom line: Pick Comet if research and grounded citations matter most and you are ready to switch browsers.
3. Arc Max, native browser AI in Arc
Arc Max is the AI layer inside The Browser Company’s Arc. Highlight anything, hit shift-space, and Arc summarises, explains, or renames the tab intelligently. Ask on Page keeps the sidebar quiet and only surfaces when you ask.
Where it falls short: Arc is macOS-native (Windows in beta). Development pace on Arc slowed after 2024, so future roadmap is uncertain.
Pricing:
- Free: Arc Max is included with Arc
- Paid: None yet
Platforms: macOS, Windows (beta)
Download: Arc.net
Bottom line: Pick Arc if you already like Arc’s philosophy. Skip if you need Windows-first stability.
4. SigmaOS, workspace-oriented AI browser
SigmaOS is a workspace browser that treats tabs as tasks. Its Airis assistant (sidebar) reads the current tab or workspace, drafts replies to Gmail threads in the panel, and can queue actions across the tabs in a workspace. If you work like your browser is your operating system, this is a strong fit.
Where it falls short: macOS-only. Workspace metaphor is not for everyone.
Pricing:
- Free: Basic tier
- Paid: SigmaOS Plus around $10 per month
Platforms: macOS
Download: SigmaOS.com
Bottom line: Pick SigmaOS if you like workspace browsers. Skip on Windows or Linux.
5. Page Assist, fully local sidebar for Ollama
Page Assist is an open-source browser extension that turns your Chrome, Firefox, or Edge sidebar into a chat window backed by your local Ollama endpoint. Page-aware summarise, ask, and translate all run against your local model, so nothing leaves the machine. Model picker is inside the sidebar, so switching between llama3.1 and qwen2.5 is one click.
Where it falls short: You need Ollama installed and running. No hosted fallback.
Pricing:
- Free: Fully free and open source
- Paid: None
Platforms: Windows, macOS, Linux (Chrome, Firefox, Edge, Brave)
Download: GitHub Chrome Web Store
Bottom line: The private sidebar for people running local models. Skip if you have no local model runtime.
6. Monica, sidebar with an app-store of prompts
Monica installs as an extension across Chrome, Edge, Firefox, and Safari and adds a sidebar with a curated “prompt store” (translate, rewrite, chart-explain, code-review, etc.). Underneath, it can route to GPT-4o, Claude, Gemini, or your own OpenAI-compatible endpoint. The prompt store lowers the “what do I even ask” barrier for people new to sidebar AI.
Where it falls short: Free tier is small. The prompt store can feel noisy.
Pricing:
- Free: Limited quota
- Paid: Monica Pro around $9 per month
Platforms: Windows, macOS, Linux
Download: Monica.im
Bottom line: Pick Monica if you like prompt libraries and want cross-browser support. Skip if you already know your prompts.
7. Merlin, sidebar that stretches a GPT-4 quota
Merlin is a Chrome and Edge extension aimed at people who want GPT-4-quality answers without paying for ChatGPT Plus. The free tier gives you a daily quota of high-model queries, plus unlimited lower-tier queries. The sidebar covers summarise, translate, chat over a page, and YouTube summarise for videos.
Where it falls short: Free quota resets slowly on heavy use. Some features hide behind higher-cost tiers.
Pricing:
- Free: Daily quota
- Paid: Around $19 per month for unlimited GPT-4-class use
Platforms: Windows, macOS, Linux (Chrome, Edge, Brave)
Download: Merlin.foyer.work
Bottom line: Pick Merlin if you want GPT-4 quality on a budget. Skip if you already have ChatGPT Plus.
8. Brave Leo, built-in browser AI in Brave
Brave Leo is the built-in AI in the Brave browser. It runs against Brave’s hosted models by default or against your local Ollama when configured. Because it is native to Brave, there is no extension to install and it respects Brave’s privacy defaults (no chat history sent to the model provider by default).
Where it falls short: Only in Brave. Local model configuration takes a settings dive.
Pricing:
- Free: Full access on Brave
- Paid: Leo Premium around $15 per month for hosted models with higher quotas
Platforms: Windows, macOS, Linux
Download: Brave.com
Bottom line: Pick Leo if you already use Brave and want the private sidebar with no extra install. Skip if you use Chrome or Firefox.
How to pick
- If you want multi-model choice in Chrome or Edge: Sider.
- If you want cited answers and agentic actions: Perplexity Comet.
- If you already use Arc: Arc Max, no other extension needed.
- If you want a local-only sidebar: Page Assist with Ollama.
- If you want a prompt library to lean on: Monica.
- If you want GPT-4 access on a budget: Merlin.
- If you use Brave: Brave Leo, native and free.
- If you like the workspace browser shape: SigmaOS on Mac.
FAQ
Is Copilot the same as a browser sidebar AI?
Copilot in Edge is one, yes. The apps here give you the same experience in other browsers and often let you pick the model behind it.
Which browser sidebar AI is best for privacy?
Page Assist with a local Ollama model keeps everything on your machine. Brave Leo is the next-safest with sensible defaults.
Can I use these AI sidebars offline?
Only the ones that support local models (Page Assist, Sider with Ollama, Brave Leo with Ollama). The hosted-only ones need internet.
Which is the best free browser AI?
Page Assist is free and local. Brave Leo is free inside Brave. Sider’s and Merlin’s free tiers are the most usable of the hosted-only options.
Will these sidebar AIs work on Safari?
Sider, Monica, and Merlin have Safari builds. Page Assist and Brave Leo do not (Safari’s extension model does not support them yet).
