For a free start with approvals and email built in, try Hark. If you already pay for Claude, use Claude in Chrome. For an all-in-one sidebar with an operator, look at Monica. For build-your-own automations, HARPA AI. If you are in the US with Google AI Pro, Gemini’s auto browse is built into Chrome.
What we looked for
An agent extension has to do more than summarize. We looked for: real actions on pages, a clear approval model, sensible permissions, how quickly a new user gets a result, and price. Facts were checked in November 2026; this market moves monthly.
1. Hark AI Agent — best for email and everyday errands
Three modes in one side panel: Chat, Agent and Tracker. The agent acts in your current tab and always asks before send, submit, book, pay or delete. One-tap email actions for Gmail and Outlook, and a tracker for orders and deadlines. No account. Free plan with 1 request a day; Pro from $39.99 a year. Limits: small free allowance, no background or scheduled tasks, desktop Chrome only. See features.
2. Claude in Chrome — best if you already pay for Claude
Anthropic’s extension became generally available in August 2026 for all paid Claude plans. A capable, more autonomous agent with automated safety checks, and manual approval as an option. Limits: not on the free plan; Chrome desktop only. Hark vs Claude in Chrome.
3. Monica — best all-in-one sidebar with an operator
Many models, writing, translation, image tools and a Browser Operator for multi-step tasks, at a low annual price. Limits: a busy interface; account required. Hark vs Monica.
4. HARPA AI — best for custom automations
Custom commands, chained workflows and page monitoring for people who like to build. Limits: you design the steps; steeper learning curve. Hark vs HARPA AI.
Built into the browser: Gemini and Copilot
Not extensions, but worth knowing. Gemini in Chrome offers auto browse to Google AI Pro and Ultra subscribers in the US. Copilot Mode gives Microsoft Edge agent-style actions at no extra charge. See Hark vs Gemini in Chrome and Hark vs Copilot in Edge.
Chat-only sidebars
Sider, Merlin and MaxAI are good reading and writing sidebars, but we found no website-acting agent in their public feature lists. If you only need summaries and rewrites, they are fine choices: Sider, Merlin, MaxAI.
Quick picker
| You want… | Try |
|---|---|
| To start free, with approvals and email help | Hark |
| More autonomy and you pay for Claude | Claude in Chrome |
| Many models and creative tools | Monica |
| To build repeatable automations | HARPA AI |
| A built-in option in the US | Gemini auto browse |