lissy93/web-check · error · Error

URL is missing from queryStringParameters

Error message

URL is missing from queryStringParameters

What it means

screenshotHandler requires the target URL as its first argument; when the argument is falsy it throws before any validation runs. The name references AWS API Gateway's queryStringParameters object, indicating this handler is wired to a ?url= query parameter that was absent from the request.

Source

Thrown at api/screenshot.js:73

    });
    const page = await browser.newPage();
    await page.emulateMediaFeatures([{ name: 'prefers-color-scheme', value: 'dark' }]);
    page.setDefaultNavigationTimeout(8000);
    await page.goto(targetUrl, { waitUntil: 'domcontentloaded' });
    await page.evaluate(() => {
      if (!document.querySelector('body')) {
        throw new Error('No body element found on the page');
      }
    });
    const buffer = await page.screenshot();
    return buffer.toString('base64');
  } finally {
    if (browser) await browser.close().catch(() => {});
  }
};

const screenshotHandler = async (targetUrl) => {
  if (!targetUrl) throw new Error('URL is missing from queryStringParameters');
  try {
    new URL(targetUrl);
  } catch {
    throw new Error('URL provided is invalid');
  }

  log.debug(`request received: ${targetUrl}`);
  try {
    return { image: await directChromiumScreenshot(targetUrl) };
  } catch (directError) {
    log.warn(`direct chromium failed, falling back to puppeteer: ${directError.message}`);
  }
  try {
    return { image: await puppeteerScreenshot(targetUrl) };
  } catch (error) {
    if (/ENOENT|Browser was not found|Could not find Chromium/i.test(error.message)) {
      return { skipped: error.message };
    }

View on GitHub (pinned to af1a97759f)

Solutions

1. Add ?url=<full URL including scheme> to the request
2. Check the request mapping: confirm the param is read from the correct location (req.query.url vs event.queryStringParameters.url)
3. Return a 400 with guidance from your wrapper when the param is missing instead of letting it bubble as 500

Example fix

// before
fetch('/api/screenshot'); // 500: URL is missing from queryStringParameters

// after
fetch(`/api/screenshot?url=${encodeURIComponent('https://example.com')}`);

const urlParam = req.query.url;
if (!urlParam) return res.status(400).json({ error: 'url query parameter is required' });
const image = await screenshotHandler(urlParam);

const hasUrlParam = (q) => Object.prototype.hasOwnProperty.call(q, 'url') && typeof q.url === 'string' && q.url.length > 0;

try { await screenshotHandler(q.url); }
catch (e) {
  if (/missing from queryStringParameters/.test(e.message)) return badRequest('add ?url=...');
  throw e;
}

When it happens

Trigger: GET /api/screenshot with no ?url parameter; the integration/handler mapping fails to extract queryStringParameters.url and passes undefined.

Common situations: Frontend forgetting to append the query param, serverless function URL vs API Gateway param-shape mismatch, or env-specific routing that drops query strings.

Understand the failure class

Background: Missing required parameter errors: what 'X is required' and 'the required X param is missing' mean, and how to fix them — this error's family across 27 libraries.

Related errors

• No target provided
• URL provided is invalid
• You must provide a URL query parameter!
• No URL specified
• Invalid URL format

AI-assisted analysis of lissy93/web-check@af1a97759f (2026-08-27). Data as JSON: /api/errors/617646a331fb7243. Report an issue: GitHub.