Tracker Weight Database

Every third-party tracking script you load costs your visitors something: bandwidth, parse time, CPU cycles, and — in many cases — their privacy. The Tracker Weight Database lets you look up the exact transfer size, decoded size, cookie count, and privacy risk rating of 100+ common trackers so you can make informed decisions about what you embed on your pages.

Why Tracker Weight Matters — Performance and Privacy

Browser performance is not a single number. It is a chain: DNS resolution, TLS handshake, download, decompression, parse, compile, execute. Each third-party tracker resets part of that chain from a domain you do not control, with latency you cannot predict.

The two size metrics that matter most are transfer size — the compressed bytes sent over the network, which determines download time — and decoded size — the uncompressed bytes the browser must parse and execute, which determines CPU cost. A script can be small on the wire but large to execute; both numbers matter.

Privacy is the second axis. Heavier trackers almost always set more cookies, join more third-party data networks, and create richer fingerprint surfaces. When you look up how cross-site trackers re-identify users, it becomes clear that script weight and identity exposure are correlated: the bigger the script, the more behavioural data it typically harvests.

For GDPR-regulated sites, there is an additional cost: any tracker requiring consent means loading a consent management platform (CMP). CMPs themselves range from 40 KB to 120 KB, so the real cost of a heavy tracker is its own weight plus the CMP overhead it mandates.

How to Use This Database

The table above is sortable and searchable. Each row shows:

• Tracker name and category — analytics, advertising, support, or identity.
• Transfer size (KB) — compressed bytes over the network.
• Decoded size (KB) — uncompressed bytes the browser parses.
• Cookies set — number of cookies written on first load.
• Privacy risk — Low / Medium / High, based on cross-site tracking capability and data-sharing practices.
• Consent required (GDPR) — whether prior opt-in is legally required in the EU.

To find a specific tracker, type its name in the search box. To compare trackers in a category, click the Category column header to sort. For a whole-page audit — the combined weight of all scripts currently loading — use the separate Script Performance Impact Calculator which aggregates across all trackers detected on a given URL.

The Heaviest Trackers by Category

Script weights vary enormously by category. The figures below are medians from our measurement runs; individual implementations may differ depending on configuration, tag management, and dynamic sub-resource loading.

Analytics

Google Analytics 4 (gtag.js) loads approximately 46 KB compressed and 128 KB decoded. When loaded via Google Tag Manager — the standard deployment — GTM adds another 82 KB compressed, making the combined analytics stack around 128 KB on the wire. Adobe Analytics typically runs 55–80 KB. Mixpanel sits at 35–50 KB depending on features enabled.

Privacy-first alternatives are a different order of magnitude. Plausible ships 1 KB. Umami is around 2 KB. Fathom loads 6 KB. None set cookies, none require a consent banner, and none phone home to ad networks.

Advertising and Retargeting Pixels

Advertising scripts are consistently the heaviest category. Criteo’s retargeting script averages 126 KB compressed. Google AdSense adds 95 KB. The Meta Pixel (formerly Facebook Pixel) is 47 KB compressed but triggers additional sub-requests that push real-world payload above 100 KB. LinkedIn Insight Tag runs 22 KB; TikTok Pixel around 36 KB.

Ad scripts also introduce the highest fingerprinting risk: they are designed to link your visitor’s session to profiles held by large ad networks, a mechanism explained in detail under how cross-site trackers re-identify users.

Support and Chat

Live chat and helpdesk widgets are an often-overlooked source of weight. Intercom’s messenger loads 75 KB on first contact. Drift runs 70 KB. Zendesk Chat (Classic) is 48 KB. Even lightweight options like Crisp add 25–35 KB. These scripts are also persistent: they load on every page, not just checkout or contact pages, because most implementations are injected site-wide via tag managers.

If live chat is a conversion tool rather than a support necessity, consider loading it only on specific pages — or replacing it with an async contact form that adds near-zero script weight.

Methodology: How We Measure Script Weight

All measurements use Chrome DevTools Protocol (CDP) via a headless Chromium instance with a cold cache profile and a standardised 20 Mbps throttled connection, which approximates median mobile network conditions in Western Europe. Each tracker is measured in isolation on a minimal host page to exclude confounding scripts. We capture three metrics:

• Transfer size — from the CDP Network.responseReceived event, encodedDataLength. This is bytes received after transport compression (gzip or brotli).
• Decoded size — from dataLength after decompression. This is what the JavaScript engine parses.
• Execution time — main-thread blocking time measured via CDP’s Performance timeline.

Each tracker is measured across five runs; the median is recorded. For trackers that load sub-resources dynamically (common in ad networks), we follow the full resource waterfall and sum all first-party loads from the tracker’s owned domains.

Marc Reuter, a former data engineer with eight years of web analytics implementation experience, designed the measurement protocol and audits the dataset quarterly. Data is refreshed when vendors ship major script updates.

Lightweight Alternatives to Heavy Trackers

Replacing a heavy tracker does not always mean losing capability. The table below maps common heavy scripts to leaner substitutes that cover the core use case.

If you are evaluating analytics replacements specifically, find a privacy-friendly analytics alternative using our guided finder, which filters by data residency, consent requirements, and pricing.

Frequently Asked Questions

How much data does Google Analytics transfer per page load?

Google Analytics 4 loaded via gtag.js transfers approximately 46 KB compressed. When loaded through Google Tag Manager (the standard method), GTM itself adds 82 KB, making the combined transfer around 128 KB per page. GA4 also sets no HTTP cookies directly — it uses first-party cookies written by the gtag snippet — but it still requires consent under GDPR because it sends personal data (IP address, User-Agent, Client ID) to Google’s servers.

Which trackers add the most weight to a page?

Advertising and consent management scripts are consistently the heaviest. Criteo (126 KB), Google AdSense (95 KB), Google reCAPTCHA (95 KB), Google Tag Manager (82 KB), Intercom (75 KB), and OneTrust CMP (65 KB) are among the largest. Ad network scripts that load dynamic sub-resources can push real-world payload well above their base transfer size.

How does GA4 compare to Plausible on performance?

GA4 via GTM transfers around 128 KB and blocks the main thread for 150–300 ms on a median mobile connection. Plausible Analytics transfers 1 KB, executes in under 5 ms, sets no cookies, and requires no consent banner. For sites where raw pageview and session data is sufficient — rather than event funnels or audience exports — the performance case for switching is substantial.

How do I find all the trackers loading on my site?

The most reliable method is to open Chrome DevTools, go to the Network tab, filter by JS, disable cache, and reload. Sort by domain to identify third-party origins. For a structured audit with privacy risk ratings, the DuckDuckGo Tracker Radar (open-source dataset) maps known tracker domains to their owners and data-sharing practices — the same dataset that underlies DuckDuckGo’s browser protection. Our database covers the most common entries from Tracker Radar with added performance measurements.

What is the DuckDuckGo Tracker Radar?

Tracker Radar is an open-source dataset maintained by DuckDuckGo that catalogues known tracking domains, their parent companies, cookie behaviour, fingerprinting APIs used, and prevalence across the web. It is updated regularly by crawling millions of pages and inspecting network requests. The dataset is publicly available on GitHub and is used in DuckDuckGo’s browser, Privacy Essentials extension, and third-party privacy tools. It differs from this database in that Tracker Radar focuses on domain-level classification, while this database focuses on per-script transfer size and performance cost.

Do tracking pixels slow down page loading?

Yes. Even a “pixel” — originally a 1×1 transparent image — has become shorthand for a JavaScript tag that may load 30–120 KB of code, write cookies, and initiate additional requests to ad-network domains. The Meta Pixel, for example, loads 47 KB of JavaScript plus dynamic sub-resources. The request itself also adds DNS lookup and connection overhead for each third-party domain. Pixels that load synchronously or early in the document can block rendering and delay Largest Contentful Paint (LCP).