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To read JSON returned by a browser action, register a waitForResponse before clicking or otherwise triggering the request, await the matching response, check its HTTP status, and then call await response.json(). Use Puppeteer or Playwright’s page-response API for traffic initiated by the page; use Playwright’s APIRequestContext when you want to make a direct API call instead.
Get a JSON response after a page action
The wait must be set up before the action. This prevents a fast response from arriving before your code starts listening. Match the endpoint closely enough to distinguish it from other requests the page may make.
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Puppeteer
const responsePromise = page.waitForResponse(response =>
response.url().includes('/api/items') &&
response.status() === 200
);
await page.click('button#load-items');
const response = await responsePromise;
const data = await response.json();
console.log(data);page.waitForResponse accepts a URL or predicate and resolves with the matching HTTPResponse. The response’s json() method parses its body and throws if the body is not valid JSON. Check status() or ok() separately from parsing. See the Puppeteer Page.waitForResponse reference and HTTPResponse reference.
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const responsePromise = page.waitForResponse(response =>
response.url().includes('/api/items') &&
response.status() === 200 &&
response.request().method() === 'GET'
);
await page.getByRole('button', { name: 'Load items' }).click();
const response = await responsePromise;
const data = await response.json();
console.log(data);Playwright’s matcher can be a URL string, regular expression, or predicate. Including the request method and expected status can help isolate the intended response. The official Page.waitForResponse documentation demonstrates creating the wait before clicking.
Check status and parse errors independently
A response can arrive with an unsuccessful HTTP status, and a successful status does not guarantee that its body is valid JSON. Treat those as separate checks. For example, if you want to report non-2xx responses instead of letting an unexpected body confuse the diagnosis:
const response = await responsePromise;
if (!response.ok()) {
throw new Error(`HTTP ${response.status()}: ${response.url()}`);
}
let data;
try {
data = await response.json();
} catch (error) {
throw new Error(`Response was not valid JSON: ${error.message}`);
}When parsing fails, inspect the response text and headers to determine whether the server returned HTML, an empty body, or another format. Puppeteer documents that HTTPResponse.json() throws when JSON.parse cannot parse the body; Playwright’s page Response also provides body-reading methods. See the Playwright Response reference.
Make a direct request with Playwright
If no browser action is needed and the goal is simply to call an endpoint, use Playwright’s APIRequestContext. This is a different workflow from observing a page’s network traffic: the returned object is an APIResponse, not the page’s Response.
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const response = await request.get('/api/items');
if (!response.ok()) {
throw new Error(`HTTP ${response.status()}`);
}
const data = await response.json();
console.log(data);APIResponse also provides body(), text(), status(), and ok(). Its body remains in memory until the request context closes; in a long-running workflow, dispose of responses after use when you want to release their bodies sooner. Consult the Playwright APIResponse documentation.
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Choose the right way to observe traffic
- One interaction, one response: use
waitForResponsewith a URL or predicate. It keeps the request tied to the action that caused it. - Ongoing or broad monitoring: use Playwright’s
page.on('response', handler)event. It receives responses as status and headers arrive; you can then decide which ones to inspect. - Direct API access: use Playwright
APIRequestContextrather than triggering page UI solely to reach an endpoint. - Request control or mocking: interception is an option when you need to modify, abort, or fulfill requests, but it is not needed for passive response reading.
Troubleshoot missing or unusable JSON
The wait never resolves
Confirm the click actually triggers the request and that the URL predicate matches the final request URL. A page may call a different endpoint, use a different method, or make several similar requests. Start with a stable path and add method or status conditions only when they match the real traffic.
The wrong response is captured
Narrow the predicate using endpoint path, request method, and, where appropriate, status. Avoid matching only a broad string such as /api on a busy page.
The response has an error status
A 404 or 503 is still an HTTP response; inspect its status and body rather than treating it as a transport failure. Playwright distinguishes an HTTP response from a request that fails before an HTTP response can be received, such as a network error. For the latter, inspect request-failure handling and network conditions.
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The body may be HTML (for example, an error page), empty, or a different format. Read response.text() where available and inspect headers before assuming the endpoint returned JSON. A successful parse alone does not prove the HTTP request succeeded.
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Considering request interception
Interception changes network flow and places responsibility on your handlers to resolve requests. The Puppeteer project’s official Request Interception guide states: “Once request interception is enabled, every request will stall unless it’s continued, responded or aborted.” Do not enable it just to read a response body; reserve it for cases such as stubbing or controlling requests.
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If the job is to capture a page image or PDF rather than inspect its JSON network response, ScreenshotNeo offers a one-request screenshot API. It accepts a URL and returns a clean PNG, JPEG, WebP, or PDF; it is not a replacement for parsing an API response.
curl -G "https://api.screenshotneo.com/v1/shot"
-d access_key=YOUR_API_KEY
--data-urlencode url=https://stripe.com
-o shot.webpSee the ScreenshotNeo API documentation for request options. Cookie and consent banners, newsletter popups, and chat widgets are removed before capture; each cleanup step can be turned off. Bot checks and CAPTCHAs, blank pages, timeouts, failed loads, and cache hits are not billed, and responses identify the page verdict and billing status in headers. ScreenshotNeo also has an MCP server with tools for AI agents to take screenshots, get page information, and capture PDFs. The Free plan includes 1,000 shots per month with no card; paid plans start at $5 for 3,000 shots.
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