Skillintermediate

Browser Rendering Gotchas

| Limit | Free | Paid | |-------|------|------| | Daily browser time | 10 min | Unlimited* | | Concurrent sessions | 3 | 30 | | Requests/minute | 6 | 180 | | Session keep-alive | 10 min max | 10 min max |

Claude Code Knowledge Pack7/10/2026

Overview

Browser Rendering Gotchas

Tier Limits

Limit	Free	Paid
Daily browser time	10 min	Unlimited*
Concurrent sessions	3	30
Requests/minute	6	180
Session keep-alive	10 min max	10 min max

*Subject to fair-use policy.

Check quota:

const limits = await puppeteer.limits(env.MYBROWSER);
// { remaining: 540000, total: 600000, concurrent: 2 }

Always Close Browsers

const browser = await puppeteer.launch(env.MYBROWSER);
try {
  const page = await browser.newPage();
  await page.goto("https://example.com");
  return new Response(await page.content());
} finally {
  await browser.close(); // ALWAYS in finally
}

Workers vs REST: REST auto-closes after timeout. Workers must call close() or session stays open until keep_alive expires.

Optimize Concurrency

// ❌ 3 sessions (hits free tier limit)
const browser1 = await puppeteer.launch(env.MYBROWSER);
const browser2 = await puppeteer.launch(env.MYBROWSER);

// ✅ 1 session, multiple pages
const browser = await puppeteer.launch(env.MYBROWSER);
const page1 = await browser.newPage();
const page2 = await browser.newPage();

Common Errors

Error	Cause	Fix
Session limit exceeded	Too many concurrent	Close unused browsers, use pages not browsers
Page navigation timeout	Slow page or `networkidle` on busy page	Increase timeout, use `waitUntil: "load"`
Session not found	Expired session	Catch error, launch new session
Evaluation failed	DOM element missing	Use `?.` optional chaining
Protocol error: Target closed	Page closed during operation	Await all ops before closing

page.evaluate() Gotchas

// ❌ Outer scope not available
const selector = "h1";
await page.evaluate(() => document.querySelector(selector));

// ✅ Pass as argument
await page.evaluate((sel) => document.querySelector(sel)?.textContent, selector);

Performance

waitUntil options (fastest to slowest):

domcontentloaded - DOM ready
load - load event (default)
networkidle0 - no network for 500ms

Block unnecessary resources:

await page.setRequestInterception(true);
page.on("request", (req) => {
  if (["image", "stylesheet", "font"].includes(req.resourceType())) {
    req.abort();
  } else {
    req.continue();
  }
});

Session reuse: Cold start ~1-2s, warm connect ~100-200ms. Store sessionId in KV for reuse.