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Browser pools let you maintain a set of identical, pre-configured browsers ready for immediate use.

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Create a pool

Create a browser pool with a specified size and configuration. All browsers in the pool share the same settings. 
import Kernel from '@onkernel/sdk';

const kernel = new Kernel();

const pool = await kernel.browserPools.create({
  name: "my-pool",
  size: 10,
  stealth: true,
  headless: false,
  timeout_seconds: 600,
  viewport: {
    width: 1280,
    height: 800
  }
});

console.log(pool.id);

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Pool configuration options

Pools can be pre-configured with options like custom extensions, supported viewports, residential proxies, profiles, and more. See the API reference for more details.

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Acquire a browser

Acquire a browser from the pool. The request returns immediately if a browser is available, or waits until one becomes available. The acquire_timeout_seconds parameter controls how long to wait; it defaults to the calculated time it would take to fill the pool at the pool’s configured fill rate. 
const browser = await kernel.browserPools.acquire("my-pool", {
  acquire_timeout_seconds: 30,
});

console.log(browser.session_id);
console.log(browser.cdp_ws_url);
The acquired browser includes all the same properties as a regular browser session, including cdp_ws_url for CDP connections and browser_live_view_url for live viewing.

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Timeout behavior

Browsers remain in the pool indefinitely until acquired. Once acquired, the pool’s timeout_seconds applies just like a regular browser timeout—if the browser is idle (no CDP or live view connection) for longer than the timeout, it is destroyed and not returned to the pool. The pool will automatically create a replacement browser at the pool’s configured fill rate.

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Release a browser

When you’re done with a browser, release it back to the pool. By default, the browser instance is reused. Set reuse: false to destroy it and create a fresh one. 
await kernel.browserPools.release("my-pool", {
  session_id: browser.session_id,
  reuse: true,
});

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Update a pool

Update the pool configuration. By default, all idle browsers are discarded and rebuilt with the new configuration. 
const updatedPool = await kernel.browserPools.update("my-pool", {
  size: 20,
  stealth: true,
});
The size parameter is always required when updating a pool, even if you only want to change other settings.
By default, updating a pool discards all idle browsers and rebuilds them with the new configuration. Set discard_all_idle: false to keep existing idle browsers and only apply the new configuration to newly created browsers.

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Flush idle browsers

Destroy all idle browsers in the pool. Acquired browsers are not affected. The pool will automatically refill with the pool’s specified configuration. 
await kernel.browserPools.flush("my-pool");

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Get pool details

Retrieve the current status and configuration of a pool. 
const pool = await kernel.browserPools.retrieve("my-pool");

console.log(pool.available_count);
console.log(pool.acquired_count);

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List pools

List all browser pools in your organization. 
const pools = await kernel.browserPools.list();

for (const pool of pools) {
  console.log(pool.name, pool.available_count);
}

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Delete a pool

Delete a browser pool and all browsers in it. By default, deletion is blocked if browsers are currently acquired. Use force: true to terminate acquired browsers and force deletion. 
// Delete a pool (fails if browsers are acquired)
await kernel.browserPools.delete("my-pool");

// Force delete even if browsers are acquired
await kernel.browserPools.delete("my-pool", { force: true });

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Full example

This example creates a pool with a capacity of 50 browsers and a fill rate of 20 browsers per minute. 
import Kernel from '@onkernel/sdk';

const kernel = new Kernel();

const pool = await kernel.browserPools.create({
  name: "scraping-pool",
  size: 50,
  fill_rate_per_minute: 20,
  stealth: true,
  headless: true,
  timeout_seconds: 300,
});

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Understanding fill rate

The fill_rate_per_minute controls how quickly the pool creates new browsers. With a capacity of 50 and a fill rate of 20:
  • Initial fill: The pool takes approximately 2.5 minutes to reach full capacity (50 browsers ÷ 20 per minute)
  • After releasing with reuse: false: If you acquire and release all 50 browsers with reuse: false, each browser is destroyed and a fresh one is created at the fill rate. Replenishing all 50 browsers takes approximately 2.5 minutes.
  • After releasing with reuse: true: The browser is immediately returned to the pool and available for the next acquire call—no wait time.
Use reuse: true (the default) when browser state doesn’t matter for your next task. Use reuse: false when you need a clean browser with no cookies, cache, or history from prior sessions.
The example below assumes you’ve already created the pool. In practice, you’d create pools once (via the SDK, CLI, or dashboard) and then acquire from them repeatedly. 
import Kernel from '@onkernel/sdk';
import { chromium } from 'playwright';

const kernel = new Kernel();

// Acquire a browser from an existing pool
const kernelBrowser = await kernel.browserPools.acquire("my-pool", {});

try {
  // Connect via CDP
  const browser = await chromium.connectOverCDP(kernelBrowser.cdp_ws_url);
  const context = browser.contexts()[0];
  const page = context.pages()[0];

  await page.goto('https://example.com');
  const title = await page.title();
  console.log(title);
} finally {
  // Release back to pool for reuse
  await kernel.browserPools.release("my-pool", {
    session_id: kernelBrowser.session_id,
  });
}

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API reference

For more details on all available endpoints and parameters, see the Browser Pools API reference.