The Tool Desk
Outbyte Driver Updater FREEFix the driver behind crashes, sound loss and screen glitchesFind Drivers →Outbyte PC Repair FREEClear out junk files and repair common Windows errorsFree Scan →Listen for the page’s request event and call request.headers() to read the headers associated with each outgoing request. You do not need request interception just to observe them. In Puppeteer 25.12.0, header names returned by this method are lowercase.
Read outgoing request headers
Register the listener before navigating so it can observe requests made during page load. The example below uses ES modules:
import puppeteer from 'puppeteer';
const browser = await puppeteer.launch();
try {
const page = await browser.newPage();
page.on('request', request => {
console.log(request.url(), request.headers());
});
await page.goto('https://example.com');
} finally {
await browser.close();
}The callback receives an HTTPRequest. Calling request.headers() returns a string-to-string object for that request. Since JavaScript object keys are case-sensitive, read a header using its lowercase key—for example, headers['content-type'].
CommonJS version
If your project uses CommonJS, replace the import line with const puppeteer = require('puppeteer');. The listener and navigation pattern are otherwise the same.
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Request headers are not response headers
request describes what the browser sends. For information about what the server returns, listen for the page’s response event and use the response API instead. A request and its response are separate events, so choose the stream that matches the information you need.
An HTTP error status does not by itself mean the request failed at the transport level: a request returning 404 or 503 still completes and emits requestfinished, rather than requestfailed solely because of its status. A redirect finishes one request and creates another for the redirected URL.
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Do you need request interception?
No—not for passive logging. Puppeteer exposes page network events by default, so attach a request listener without enabling interception when you only want to inspect headers.
Interception is for controlling individual requests, such as modifying, fulfilling, or aborting them. Once enabled, every intercepted request stalls until it is continued, answered, or aborted. A logging-only handler that forgets to resolve requests can leave page activity hanging.
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await page.setRequestInterception(true);
page.on('request', request => {
console.log(request.headers());
request.continue();
});If another listener or package might resolve the same request, check request.isInterceptResolutionHandled() before acting. Check again after any await, because another handler may have resolved it in the meantime; duplicate calls to abort(), continue(), or respond() can throw.
Add headers to requests
Use one extra header across the page
For a header to be included with every request initiated by a page, use page.setExtraHTTPHeaders(). It accepts a string-to-string object and returns a promise:
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await page.setExtraHTTPHeaders({
'x-client-tag': 'example',
});
page.on('request', request => {
console.log(request.headers()['x-client-tag']);
});
await page.goto('https://example.com');Puppeteer lowercases the header names, and the order of outgoing headers is not guaranteed.
Change only selected requests
Use request interception when a header or other change should apply only to particular requests. Interception gives you per-request control, but you must resolve every intercepted request; do not enable it solely to inspect headers.
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Troubleshoot missing or unexpected headers
- A header lookup returns undefined: Confirm the listener is on the
requestevent and use a lowercase object key such asheaders['content-type']. HTTP header names are case-insensitive, but JavaScript object properties are not. - You only want to print traffic: Remove
page.setRequestInterception(true). The request event can be observed without interception. - Page activity appears stuck: If interception is enabled, verify that every path continues, responds to, or aborts each request. A handler that only logs leaves the request unresolved.
- A request returns 404 or 503: Treat the HTTP status separately from transport failure. Such a request can still finish normally in Puppeteer’s event model.
- A redirect produces multiple log entries: Each redirected URL is a new request, so inspect the URL on each request event rather than expecting one request object to represent the entire redirect chain.
- Credentials appear in logs: Avoid indiscriminately writing authorization, cookie, or other session-related headers to production logs. Treat request headers as potentially sensitive.
Or skip the browser setup
If your goal is a website screenshot rather than inspecting Puppeteer’s outgoing headers, ScreenshotNeo provides a screenshot API and MCP server. A single GET request can return an image or PDF; its screenshot endpoint is documented at ScreenshotNeo’s API docs.
curl -G "https://api.screenshotneo.com/v1/shot" -d access_key=YOUR_API_KEY --data-urlencode url=https://example.com -o shot.webpIt removes cookie banners, newsletter popups, and chat widgets before capture. Bot checks, blank pages, failed loads, timeouts, and cache hits are not billed; responses identify page verdict and billing status in headers. AI agents can take screenshots through its MCP server. The Free plan includes 1,000 shots per month with no card, and paid plans start at $5 for 3,000 shots.
Sign up for ScreenshotNeo’s free 1,000 monthly screenshots—no card required.
Version note
The API behavior and examples here reflect Puppeteer 25.12.0. Check the current API reference if you are using a substantially different release.
Frequently Asked Questions
Why are Puppeteer request header names lowercase?
Puppeteer’s `HTTPRequest.headers()` API returns the header-name keys in lowercase; use the lowercase key when accessing the returned JavaScript object.
Does a 404 trigger Puppeteer’s `requestfailed` event?
Not solely because of the HTTP status. A 404 or 503 is still a completed request in Puppeteer’s event model.
Quick Recap
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