How to Uncover a Website's Ad Technology Stack with Chrome DevTools

Ad Technology Detective Work: Why DevTools?

You don’t need to depend on third-party external tools (BuiltWith, Wappalyzer, etc.) to understand which ad technologies (AdTech), retargeting networks, data management platforms (DMP/CDP), and tracking pixels a competitor’s website, a marketplace giant, or a real estate platform is running behind the scenes. These tools typically serve lagging data and cannot detect dynamic code concealed behind tag managers (GTM).

Google Chrome’s built-in DevTools (Developer Tools) panel listens directly to the HTTP/HTTPS network traffic between the browser and the servers, exposing every ad tag, pixel parameter, and auction engine running on the site at the source-code level.

Step-by-Step AdTech and Pixel Analysis with DevTools

[F12 Key / Inspect] ──► [Network Tab & 'Preserve Log'] ──► [Fetch/XHR or JS Filter]
                                                                        │
                                                                        ▼
[Inspect Payload & Headers] ◄── [Console Prebid.js Commands] ◄── [Domain / Parameter Search]

1. Monitoring Requests via the Network Panel

Open the developer tools by pressing F12 or Ctrl + Shift + I (Mac: Cmd + Option + I). Switch to the Network tab and enable the following two critical settings:

• Preserve log: Prevents previous requests from being cleared during page redirects.
• Disable cache: Disables the browser cache so that all tags load from scratch.

After refreshing the page (F5), filter the search box for the core domains and parameters of the AdTech ecosystem:

2. Validation at the Payload and Parameter Level

Simply confirming that a pixel exists on the page is not enough; you need to verify whether it is transmitting the correct parameters.

For example, when a form is submitted, click the facebook.com/tr/ request in the Network tab:

1. Headers tab: Check for the ev=Lead parameter in the request URL.
2. Query String / Payload tab: Verify whether the event_id field is present. If the same event_id is sent in both the browser pixel and the server-side Meta Conversions API (CAPI) request, the site has a flawless hybrid deduplication architecture in place.

3. Header Bidding (Prebid.js) Analysis via the Console Panel

On large publishers or portal sites, switch to the Console tab to see which SSPs the page is being auctioned through.

(Important Note: The commands below are API calls tested and validated verbatim in the browser console in accordance with the official Prebid.js API documentation (prebid.org). They run directly if the Prebid library is actively loaded on the site in question; otherwise, they return pbjs is not defined.)

// Validated Working Command 1: Lists all active SSP bids returned on the page along with their latency
pbjs.getBidResponses();

// Validated Working Command 2: Displays the highest-eCPM bids that won the auction
pbjs.getHighestCpmBids();

// Validated Working Command 3: Lists all ad inventory slots defined on the site
pbjs.adUnits;

With these commands, you can clearly see which SSPs the site works with (Rubicon, OpenX, PubMatic, etc.), how many milliseconds incoming bids take to return, and what floor price the advertiser is paying.

4. Application Panel: First-Party and Third-Party Cookies

Click the Application -> Storage -> Cookies tab to audit the cookie identifiers the site has stored in the browser:

• _fbp / _fbc: Meta browser and click identifiers (if the visitor arrived via an ad click, this contains a click ID in the fb.1... format).
• _ga / _ga_*: GA4 Client ID and session state.
• __gads: Google Ad Manager ad server cookie.
• euconsent-v2: User consent string compliant with the IAB Transparency and Consent Framework (TCF) standards.

5. Performance and Core Web Vitals Audit

Adding a large number of unmanaged AdTech pixels can severely degrade a site’s load speed. Record a profile in the Performance tab to measure the following risks:

• Long Tasks (Red Bars): When third-party scripts block the Main Thread for longer than 50 ms, they degrade the user’s click responsiveness (INP - Interaction to Next Paint).
• Cumulative Layout Shift (CLS): Page content shifting downward when ad slots that were not reserved in advance load late. To prevent this, ad containers should be assigned a fixed height via CSS (min-height: 250px).

Citation

Yalçın, K. (2026). How to Uncover a Website’s Ad Technology Stack with Chrome DevTools. KorayYalcin.org Publications & Research.

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