如何查看浏览器获取动态内容的XHR？Firefox无法显示XHR请求怎么办？

Hey there, I’ve run into this exact frustration when building scrapers—nothing’s more annoying than knowing an API exists but not being able to see the calls! Let’s walk through the most likely fixes and checks to get those requests showing up:

First, Double-Check You’re Looking in the Right Spots #

• Don’t restrict yourself to just the XHR filter. Some sites use Fetch API calls (modern Firefox groups these under XHR, but older versions might have a separate Fetch tab), or even load data via script tags (like JSON-P responses). Switch to the All tab and use the search bar to filter for json—this will catch any request with JSON in the URL or response.
• Make sure you’ve enabled Disable cache in the Network tab settings (click the gear icon in the top-right of DevTools). Even manual cache clears can miss something, so this ensures DevTools captures every request during your session.

Confirm the Request Triggers After Initial Load #

A ton of sites load data dynamically—only when you scroll, click a button, or navigate to a specific section. If you just refresh and wait, the API call might never fire. Try this:

1. Keep DevTools open with the Network tab active
2. Perform the action that should load the dynamic data (e.g., scroll down, click "Load More")
3. Watch the Network tab as you act—you should see the request pop up in real time.

Rule Out Extension or Privacy Blocking #

Ad blockers, privacy extensions (like uBlock Origin or Privacy Badger), or even Firefox’s built-in Enhanced Tracking Protection can block API requests without you noticing. Test this by:

• Disabling all extensions temporarily (head to about:addons to manage them)
• Opening the site in Firefox’s Private Browsing Mode (which disables most extensions and uses a fresh cache)
• If that works, add the site or its API domain to your extension’s whitelist to keep accessing the requests.

Check for JavaScript Errors or Service Worker Interference #

• Switch to the Console tab and scan for red error messages. A broken script might be preventing the XHR/Fetch call from executing at all. Understanding the error can also help you replicate the request correctly in your scraper.
• Some sites use Service Workers to cache or intercept requests, making them invisible in the Network tab. To disable this:
  1. Go to the Application tab in DevTools
  2. Expand the Service Workers section
  3. Click Unregister for any active workers linked to the site
  4. Refresh the page and check the Network tab again.

Use the Performance Tab to Dig Deeper #

If all else fails, the Performance tab can uncover hidden requests:

1. Go to the Performance tab
2. Click the record button (circle icon)
3. Perform the action that should load the dynamic data
4. Stop recording
5. Scroll through the timeline to find network events—this will show every request made during the session, even if it didn’t appear in the Network tab. Clicking a request gives you full details like URL, headers, and response.

Final Quick Checks #

• Make sure you’re running the latest Firefox version—older builds can have DevTools bugs that hide certain requests.
• If the API requires authentication (cookies, tokens), ensure you’re logged into the site in the same browser session where you’re using DevTools. Without proper auth, the request might fail silently or not be sent at all.

Hopefully one of these steps gets those XHR requests visible so you can replicate them in your Python scraper!

内容的提问来源于stack exchange，提问作者Reinaldo Chaves