Which Browser Did Claude Just Open?

August 26, 2026 - Predict and test which browser Cowork opens.

Introduction

30 Second Summary

You ask an AI assistant to check a webpage, and a browser opens. Is it your browser with all your saved logins, or a completely separate one that knows nothing about you?

In this project, you will test which browser Claude's Cowork actually opens when you give it a web task. You will write predictions before touching anything, then compare them against what you observe.

What You'll Build

You hand Claude the same Wikipedia request under different browser settings, watch which browser surface appears each time, and walk away with a dated log of predictions versus real observations.

By the end of this project, you'll have:

A dated record of whether the built-in browser has reached your account during its rollout week, with your plan tier. Mid-rollout, this snapshot is the only version anyone can have. Once the rollout finishes, it is unrecoverable.
Direct observations of which browser Claude actually opens under each Preferred browser setting, compared against predictions you wrote before touching anything.
A record of which source browsers the login-import offer names on your platform, compared against the vendor's published list, without importing anything.
Secret Mission: Apply the same predict-toggle-observe method to another tool that recently added a second way to do something you already do.

Are there any prerequisites?

You need a paid Claude plan (Pro, Max, or Team) and Google Chrome installed. If you already have the Claude Desktop app or the Claude in Chrome extension, you will skip those install steps rather than reinstalling.

Before We Start

Before you install anything or open a single setting, this step locks in what you expect to happen. Writing three predictions now gives you something concrete to compare against when you run each test later.

Set Up and Check for Arrival

Anthropic announced on 26 August 2026 that Cowork now includes a built-in browser, rolling out over the following week to Pro, Max, and Team plans. Before you can test which browser opens for your tasks, you need the right tools set up and an answer to a more basic question: has the feature reached your account yet?

Mid-rollout, "not yet" is a real finding. Once the rollout finishes, that observation becomes unrecoverable.

In this step, get ready to:

Install or confirm the Claude Desktop app and sign in with your paid plan.
Install or verify the Claude in Chrome extension and connect it to Claude Desktop.
Check whether the Preferred browser option has appeared and record the finding with today's date.

Install or open Claude Desktop

The Claude Desktop app is where Cowork runs. You need it installed and signed in with your paid Claude account to proceed.

✔️ I already have Claude Desktop

Press Cmd+Space (macOS) or the Windows key (Windows) to open your search bar.
Type Claude and press Enter to open Claude Desktop.
Confirm you are signed in by checking for your initials in the lower-left corner of the window.

ⓧ I need to install it

Open your browser and go to claude.ai/download.
Download the installer for your operating system.
Install the app by dragging it to Applications (macOS) or running the downloaded .exe installer (Windows).
Press Cmd+Space (macOS) or the Windows key (Windows) to open your search bar.
Type Claude and press Enter to open Claude Desktop.
Sign in with your paid Claude account (Pro, Max, or Team).
Confirm you see your initials in the lower-left corner of the window.

On Linux?

The Claude Desktop app is available for Linux, though the install path may differ. Check the download page for platform-specific instructions.

Can't sign in?

Make sure you have a paid Claude plan (Pro, Max, or Team). Cowork is not available on free accounts.

If you are on an Enterprise plan, your admin needs to enable Cowork in Organization settings. This project is scoped to Pro, Max, and Team plans.

Still stuck? Help me sign in to Claude Desktop with my paid account.

Set up the Claude in Chrome extension

The Claude in Chrome extension lets Claude interact with web pages through your real Chrome browser. You need it installed and connected to Claude Desktop so you can compare both browser surfaces later.

✔️ I already have the extension

No action needed here. Move on to connecting the extension to Claude Desktop below.

ⓧ I need to install it

Press Cmd+Space (macOS) or the Windows key (Windows) to open your search bar.
Type Google Chrome and press Enter to open it.
Navigate to the Claude in Chrome extension page in the Chrome Web Store.
Click Add to Chrome.
Grant the requested permissions when prompted.
Confirm the Claude icon appears in your Chrome toolbar.

In Claude Desktop, click your initials in the lower-left corner.
Select Settings.
Click Connectors.
Click Configure next to Claude in Chrome.
Check whether the toggle is set to on.
If it is off, click it to turn it on.

You should see the Claude in Chrome connector with its toggle in the on position.

What does the connector do?

The connector lets Claude Desktop communicate with your Chrome browser through the extension. With it enabled, Cowork can route web tasks to Chrome when the Preferred browser setting directs it to.

Don't see Claude in Chrome in Connectors?

Make sure the Claude in Chrome extension is installed in Google Chrome. Other Chromium-based browsers are not supported.

Need a hand? Help me find the Claude in Chrome connector in my Claude Desktop settings.

Check whether the built-in browser has arrived

The Preferred browser option under Cowork in your settings is the signal that the built-in browser has reached your account.

In Claude Desktop Settings (click your initials in the lower-left corner if you navigated away), look for Cowork in the menu.

Before you look further, take a guess. Do you expect the Preferred browser option to be in your settings today?

Under Cowork, look for a Preferred browser option.

✔️ I see the Preferred browser option

The built-in browser has reached your account.

Record today's date.
Record your plan tier (Pro, Max, or Team).
Record that the Preferred browser option is present.
Note which option is currently selected.

Keep this dated record alongside the three predictions you wrote down earlier. You will compare against them in the following steps.

ⓧ I don't see it

The feature has not reached your account yet. This is a complete finding on its own.

Record today's date.
Record your plan tier (Pro, Max, or Team).
Record that the Preferred browser option is absent under Cowork.

Your project is complete with this observation. A mid-rollout absence, dated with your plan tier, is the kind of data point that vanishes once everyone has the feature. Skip ahead to Before You Go to wrap up.

Why is absence a complete finding?

During a staged rollout, not everyone gets the feature on the same day. Recording that the feature had not arrived on a specific date, under a specific plan tier, captures something that becomes unrecoverable once the rollout finishes and every account has it.

Your tools are ready and you have your first dated finding on record. Next up, you will give Claude a web task and watch which browser surface actually opens.

One Task, One Observation

Your tools are installed and you have a dated record of whether the built-in browser has reached your account. Now it is time to see which browser actually opens when Claude Desktop handles a web task.

You have two browser surfaces available but you have not watched either one activate from a Cowork task yet. Anthropic says that if you already use Claude in Chrome, "that stays your default." Before touching any settings, you need a baseline observation to test that claim.

In this step, get ready to:

Run a Cowork web task and watch which browser surface opens.
Record your observation and compare it against your first prediction.

Give Claude a web task

Before you run anything, look at your first prediction from Step 0. Which browser did you predict would open when Claude handles a web task?

In Claude Desktop, start a new Cowork task.
Type the following request and send it:

Go to en.wikipedia.org and tell me the title of today's featured article.

Why this request?

This request forces Claude to open a browser because it needs to visit a live web page. Wikipedia requires no sign-in, so the result does not depend on which browser sessions you are logged into.

Record which browser opened

Watch your screen. One of two things happened: a browser panel opened inside the Cowork side panel, or a Chrome tab opened in your real browser.

Record exactly which browser surface opened. Write down whether it was the Cowork built-in side panel or a Chrome tab in your real browser.
Record what you saw, not what the Preferred browser setting says is selected.
Write this observation next to your first prediction. Note whether your prediction matched what actually happened.

What is the difference between the two browsers?

The built-in browser uses a clean browser profile, separate from your personal browser, with none of your saved logins or history. It opens inside the Cowork side panel.

The Claude in Chrome extension uses your real Chrome browser with your existing login state. When it activates, you will see a new tab open in Chrome itself.

Nothing opened?

If Claude answered the question without opening any browser, it may have used cached knowledge instead of visiting the page. Try rephrasing the request to make the live visit explicit, such as asking Claude to open the page and read the current content.

If you see an error or Claude says it cannot browse, confirm that the Preferred browser option is present under Settings then Cowork. If it is not there, the rollout has not reached your account and your project is complete with that finding.

Still stuck? Help me figure out why Claude is not opening a browser for my Cowork web task.

You should now be able to describe which browser surface opened and have that observation written down next to your first prediction.

You have your baseline. Next, you will flip the Preferred browser setting and run the same task again to find out if the other browser takes over.

Switch, Repeat, Reverse

In the last step, you ran a web task and watched which browser Claude opened. That was one observation under one setting.

One data point does not prove that a toggle works. Until you flip it and watch, the label is just a label.

In this step, you will switch the Preferred browser setting, run the same task, and see whether the browser changes. Then you will switch it back to confirm the setting works in both directions.

In this step, get ready to:

Toggle the Preferred browser setting and run the same web task.
Switch the setting back and confirm the original browser returns.
Record the exact wording of both Preferred browser options.

Note the current setting and switch it

Before you change anything, you need to record what the setting says right now. The exact wording of each option is evidence you cannot recover later.

In Claude Desktop, click your initials in the lower-left corner.
Select Settings.
Select Cowork.
Find Preferred browser and note which option is currently selected.
Write down the exact wording of the selected option.
Click the other option to switch to it.
Write down the exact wording of this second option too.

The setting now shows the other option selected.

Why record the exact wording?

The exact wording of each option tells you what the vendor claims the toggle does. If the setting turns out not to change which browser opens, that wording is the evidence of what was promised versus what was delivered.

Run the task and watch which browser opens

Before you run the next task, think about your second prediction. Do you expect a different browser to open now, or the same one as your baseline in Step 2?

Start a new Cowork task in Claude Desktop.
Give Claude the same request: "Go to en.wikipedia.org and tell me the title of today's featured article."
Watch which browser surface opens. Did a browser panel appear inside the Cowork side panel, or did a Chrome tab open in your real browser?
Record this as Observation 2 next to your second prediction.

Did the browser change? If a different browser opened this time, the setting routed your task the way the label promised.

What if the same browser opened both times?

That is a valid finding, not an error. Record it carefully alongside the exact wording you noted. The wording tells you what the vendor claimed the toggle would do versus what it actually did on your account.

No browser opened at all?

Make sure you started a new Cowork task, not a continuation of a previous conversation. Your request must specifically ask Claude to visit a website so it needs to open a browser.

Help me figure out why Claude is not opening a browser for my Cowork web task.

Switch back and confirm the reversal

You have tested the setting in one direction. A setting you have only ever moved one way is one you have not fully tested. The reversal proves it controls routing both ways.

Return to Settings in Claude Desktop (click your initials in the lower-left corner).
Select Cowork, then find Preferred browser.
Switch the setting back to its original value (the one that was selected before you changed it earlier).

Before you run the task one more time, what do you expect to see? The same browser as your baseline from Step 2, or something different?

Start a new Cowork task in Claude Desktop.
Give Claude the same request: "Go to en.wikipedia.org and tell me the title of today's featured article."
Watch which browser surface opens.
Record this as Observation 3.

Observation 3 should match Observation 1, your baseline from Step 2. If it does, the setting controls browser routing in both directions.

What should I see?

Check your log. You should now have three observations, each with a browser surface recorded: the baseline from Step 2, the switch from this step, and the reversal you just ran. The exact wording of both Preferred browser options should also be recorded.

If the reversal produced the same browser as the baseline, you have confirmed the setting works in both directions. If it did not, that mismatch is a finding worth recording in detail.

Reversal did not match the baseline?

Confirm you switched the setting all the way back to the original option, not a third option or the same one you just tested. The wording you recorded earlier is your reference.

Help me figure out why the reversal produced a different browser than my baseline.

You have proven the setting controls browser routing in both directions. Next, you will look at what the built-in browser would need from your real browser to carry your identity.

Read the Login-Import Offer

You have proven the Preferred browser setting controls routing in both directions. One question remains from your predictions: what would the built-in browser need from your real browser to carry your identity?

The built-in browser starts as a clean profile with none of your saved logins or history. This step is about finding its cookie-import offer and reading it without accepting it.

In this step, get ready to:

Find the login-import offer inside the built-in browser.
Record which source browsers the offer names on your platform.
Compare the observed list against the vendor's published per-platform list.

Set the preferred browser and find the import offer

The built-in browser needs to be the active browser surface for this step. If your Preferred browser setting is still pointed at the other option after your reversal in Step 3, you will switch it now.

Return to the Preferred browser setting by clicking your initials in the lower-left corner of Claude Desktop.
Select Settings.
Navigate to Cowork, then find Preferred browser.
If the built-in browser is not already selected, switch to it.

Now you need the built-in browser to actually open so you can look inside it.

Start a new Cowork task with any simple web request that does not require a sign-in, such as: "Go to en.wikipedia.org and tell me the title of today's featured article."
Watch for the built-in browser to open in the Cowork side panel.
Inside the built-in browser panel, look for an option to import cookies or sign-in state.

What is the vendor's description of this feature?

The Cowork product page describes this as the ability to "import cookies to stay signed in to your browser." The import offer connects the clean, isolated built-in browser to the login state of your real browser.

Can't find the import offer?

Make sure the built-in browser actually opened in the side panel. If a Chrome tab opened instead, the Preferred browser setting is still pointed at the Claude in Chrome extension. Switch it to the built-in browser option and try a new task.

If the built-in browser is open but you do not see an import option, try navigating to a page that would normally require sign-in. The offer may appear when the browser encounters a site where cookies would matter.

Help me find the cookie-import offer in the Cowork built-in browser.

Read the dialog and import nothing

You have found the import offer. The goal now is to read it carefully and record what it says. No credential is moved at any point in this project.

Read the dialog or prompt that appears.
Note which source browsers it lists on your platform (for example, it might name Chrome, Edge, Firefox, or some subset).
Record those browser names in your observations log as Observation 4.
Do not click any import button.
Do not check any boxes.
Close or dismiss the offer without accepting it.

Do not import anything

Moving a credential is not undone by unchecking a box later. The vendor does not describe an undo mechanism for cookie import.

A thirty-minute exercise is not the place to make an irreversible decision about where your cookies live. This step is about reading the offer, not accepting it.

Compare against the vendor's published list

Before you compare, pull up Prediction 3. You wrote down which source browsers you expected the login-import offer to name on your platform. Do you think your prediction was right?

Here is the vendor's published per-platform list, quoted from the Cowork product page of 26 August 2026:

macOS: Chrome, Edge, and Firefox.
Windows: Firefox.
Linux: Firefox.

Compare the source browsers you recorded in Observation 4 against this list for your platform.
Record whether your platform's offer matches the vendor's published list.
Write your finding next to Prediction 3.

What if my list does not match?

A mismatch is a valid finding. The vendor's published list is from a specific date during a staged rollout. What you actually see on your platform may differ. Record the difference exactly as you observe it.

You now have a record of which source browsers the login-import offer named on your platform, compared against the vendor's published per-platform list. You have not imported anything.

Secret mission

Point the Method Somewhere Else

You built a method across four steps: predict, observe, toggle, reverse. Now pick another tool you use that recently added a second way to do something you were already doing. Test whether its setting between the two paths is real.

Clean Up Your Resources

Decide whether to keep your resources running, pause them to come back later, or delete them entirely.

This project uses your existing Claude subscription and runs entirely on your desktop. There are no ongoing costs from anything you did here.

Resources you used:

Claude Desktop app.
Claude in Chrome extension.

Keep everything running

No action needed. Choose this if you use Claude Desktop regularly and want the built-in browser and Chrome extension available.

Your Preferred browser setting is currently set to the built-in browser. Change it anytime in Settings, then Cowork, then Preferred browser.
Your observations and predictions logs document a moment inside a staged rollout. That dated record is not recoverable once the rollout finishes.

Pause - I'll come back to this later

Reset the Preferred browser setting to your everyday preference. The apps stay installed and ready for next time.

In Claude Desktop, click your initials in the lower-left corner and select Settings.
Navigate to Cowork, then Preferred browser.
Set it to whichever option you prefer for daily use.

Delete - I don't want to use this again

Remove the extension and the desktop app if you installed them for this project. Skip any item you had before starting.

In Google Chrome, right-click the Claude icon in your toolbar and select Remove from Chrome.
On macOS, open Finder and go to Applications. Drag Claude to the Trash.
On Windows, open Settings and select Apps. Find Claude and click Uninstall.

Nice Work!

Nice work! You started with three predictions, tested every one of them, and now have a dated record of exactly which browser Claude opens and why.

What you learned:

Recorded whether the Cowork built-in browser reached your account during rollout week, with today's date and your plan tier, capturing a finding that disappears once the rollout finishes.
Gave Claude the same web task under both Preferred browser settings, confirmed the reversal, and recorded which browser surface actually opened each time against the predictions you wrote before touching anything.
Read the login-import offer without accepting it and compared the source browsers it names on your platform against the vendor's published per-platform list.
Secret Mission: Applied the same predict-then-observe method to another tool that recently added a second way to do something you already do, and tested whether its setting between the two paths is real.

Ready to quiz yourself?