Kernel vs Steel

The decision

Start with the product contracts for credential handling, website sign-in, code execution, scheduled execution. Different labels do not establish different functionality; compare the implementation and conditions behind each one.

Kernel provides cloud browsers and an app platform for TypeScript or Python code. App actions run alongside Kernel browsers, while profiles and Managed Auth handle retained state and sign-in connections.

Steel is a browser API with managed cloud and self-hosted deployment paths. Its current documentation covers persistent profiles, a credential API, session replay and agent observability.

At a glance

Sources: kernel.sh [1] ↗kernel.sh [2] ↗kernel.sh [3] ↗kernel.sh [4] ↗kernel.sh [5] ↗kernel.sh [6] ↗docs.steel.dev [7] ↗docs.steel.dev [8] ↗docs.steel.dev [9] ↗docs.steel.dev [10] ↗docs.steel.dev [11] ↗docs.steel.dev [12] ↗

What survives a session

Kernel: Profiles preserve browser user-data-directory state, including cookies, site data, tabs and preferences. Profile sharing and save behavior need explicit treatment when parallel workers use seeded state.

Steel: The Profiles API documents reusable browser context, cookies, extensions, credentials and browser settings. Steel also documents lighter auth-context reuse, which should not be confused with a complete profile.

Sources: kernel.sh [1] ↗docs.steel.dev [2] ↗

Website login

Kernel: Managed Auth handles website login and eligible connection recovery. Vault fill is a separate flow for applications that control navigation and form submission; the reviewed vault documentation labels that surface as preview.

Steel: Steel's Credentials API stores credentials for users or agents. Its cookbook demonstrates using stored credentials with Playwright, while profiles and auth contexts preserve signed-in browser state.

Sources: kernel.sh [1] ↗docs.steel.dev [2] ↗

Where the code runs

Kernel: Deploy a TypeScript or Python App and expose Actions that callers invoke. Kernel co-locates code with the browser environments the app creates. An Action invocation is the execution unit rather than a bare CDP connection.

Steel: The reviewed browser documentation establishes sessions, profiles and credentials. It does not establish a hosted Python handler with deployment and invocation APIs. An external worker can control a Steel browser; price and operate that worker separately.

Sources: kernel.sh [1] ↗docs.steel.dev [2] ↗

Published browser measurements

These are the latest provider runs in the saved BrowserArena snapshot checked on October 18, 2026. Dates and runner environments can differ. A lifecycle test opens, connects, navigates and releases a browser; the throughput test runs a separate browser action sequence. Neither measures managed authentication or deployed Function reliability.

Use these observations to choose what to test in your application. An account-configuration failure, an incompatible page action and a timed-out navigation require different interpretations. BrowserArena is maintained by Notte and publishes its source and methodology.

Sources: browserarena.ai [1] ↗browserarena.ai [2] ↗github.com [3] ↗

Pricing model

Kernel: Use the plan and browser configuration in Kernel's pricing documentation. Managed networking, account allowances and app execution make a browser-hour comparison only one part of the decision.

Steel: Hosted browser plans and a self-hosted browser have different cost structures. For self-hosting, include the worker, compute, networking, storage and operations rather than assigning the open-source code a zero operating cost.

Sources: kernel.sh [1] ↗docs.steel.dev [2] ↗

Capacity and limits

Kernel: Kernel documents concurrent browsers, browser creation rate and per-browser resources separately. Standby browsers can still consume concurrency. Pools change how browsers are acquired; they do not erase account limits.

Steel: Steel's pricing and limits page describes hosted account entitlements. For a self-hosted deployment, capacity depends on the resources and orchestration you operate as well as the browser process.

Sources: kernel.sh [1] ↗docs.steel.dev [2] ↗

Which approach fits?

Choose Kernel when your code makes many browser calls and you want to deploy it beside the browser, or you need Kernel's managed sign-in flow.

Kernel tradeoff: Browser-local code changes the deployment model. Check app action behavior, account limits and persistent-state ownership before moving an external worker into it.

Choose Steel when you want browser infrastructure that can fit a self-hosted deployment, with profiles and credentials available through browser-focused APIs.

Steel tradeoff: Hosted and self-hosted Steel are different operating choices. A cloud feature's documentation does not establish identical packaging, retention or operational support in a self-hosted installation.

Sources: kernel.sh [1] ↗docs.steel.dev [2] ↗

Check the browser connection

Install playwright-core in your application and provision a session through the provider's documented creation flow. Run this smoke test from the intended controller region with the returned CDP endpoint. It checks connection and navigation, not login, rendering parity or a complete business workflow.

Keep browser connection URLs on your backend. After the test, release the owned session through the provider's API. Product-specific lifecycle APIs and profile identifiers are not portable between providers.

import { chromium } from "playwright-core";

// Provision the owned browser using the provider's documented session API.
// Keep the connection URL in your backend's secret environment.
const endpoint = process.env.BROWSER_CDP_URL;
if (!endpoint) throw new Error("Set BROWSER_CDP_URL for an owned session");

const browser = await chromium.connectOverCDP(endpoint);
try {
  const context = browser.contexts()[0] ?? await browser.newContext();
  const page = context.pages()[0] ?? await context.newPage();
  await page.goto("https://example.com", { waitUntil: "domcontentloaded" });
  if ((await page.title()) !== "Example Domain") {
    throw new Error("The browser did not reach the expected page");
  }
  console.log({ connected: true, expectedPage: true });
} finally {
  await browser.close();
  // Release the owned session with the provider's documented API as well.
  // A disconnected socket alone is not a portable session-cleanup contract.
}

Sources: playwright.dev ↗

Before you switch

Keep the same target workflow when evaluating both products. Separate infrastructure facts from measurements and test the required account state, action sequence and artifacts. A successful connection test does not establish that a long or authenticated task will complete.

Use the focused guides for Kernel and Steel below when the deciding requirement is pricing, persistence or code execution. Provider-owned resources such as session IDs, profiles and managed connections need a new mapping during migration.

When Notte belongs on this shortlist

Kernel's browser-local Apps make execution placement part of the decision. Compare the repeated action path with the proposed Notte controller or Function deployment before concluding that a lifecycle or hourly-rate difference decides the workflow.

Steel's managed and self-hosted choices make infrastructure ownership a concrete deciding factor. Keep that option on the shortlist when operating the browser is intentional; evaluate Notte when owning fewer execution and authentication components is the actual goal.

Notte: Create an owned browser session, connect Playwright or Puppeteer over CDP, and stop the session when the work finishes. Browser lifecycle management remains necessary even when the control socket disconnects.

Consider this third option when its documented mechanism addresses a requirement left open by the two providers above. A working configuration on either original provider can still be the better choice; compare the task and ownership cost before switching.

Sources: kernel.sh [1] ↗docs.steel.dev [2] ↗docs.notte.cc [3] ↗

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