I have compiled a list of Chrome extensions that I use in my work as a web analyst. Some of them on a daily basis. With these extensions, you can easily
- verify the correct implementation of Google Tag Manager, including dataLayer
- verify the implementation of Google Analytics 4 and Google Ads codes
- verify the implementation of Facebook, Twitter, TikTok or Microsoft Ads pixels
- investigate what web technologies and marketing codes are used on any website
- troubleshoot Content Security Policy (CSP) or easily send HTTP requests (useful for testing Google Analytics Measurement Protocol or testing various APIs)
Google Analytics & GTM / dataLayer Tools
GTM/GA Debugger 
Analytics Debugger Extension. Get your analytics implementations debugged without hassles
My number 1 extension. It shows GTM dataLayer and Google Analytics 4 (GA4) or Universal Analytics requests in detail. It shows a history of all requests for all pages. Compared to some other tools it has a clean and intuitive interface.
Average rating: 4.6 (by 107 users).
Chrome extension downloads: 90,000+
WASP.inspector: Analytics Solution Profiler 
Digital analytics quality made easy
My number 2 extension used 5+ years. WASP.inspector for Google Chrome is an invaluable web analytics quality assurance tool for managers, marketers, and implementation specialists who need to audit, validate, and debug data sent from websites via tags and beacons.
By providing a robust and comprehensive tool for managing, validating, and debugging data, WASP.inspector ensures that managers, marketers, and other professionals have the most up-to-date information at their fingertips.
Average rating: 4.5 (by 185 users).
Chrome extension downloads: 50,000+
Datalayer Checker 
The easiest way to debug and check the dataLayer implementations without having to use the browser console!
Sublimetrix has released Datalayer Checker 2, a Chrome extension that makes it easy to debug and check dataLayer implementations without using the browser console.
It includes features such as flat and JSON view, copy-to-clipboard variables, auto pushes coloring, custom coloring rules, syntax coloring, and more.
Average rating: 4.7 (by 27 users).
Chrome extension downloads: 100,000+
dataslayer 
Debug and test tag management (Google Tag Manager, DTM, Tealium) and analytics implementations.
dataslayer is a Chrome extension that helps debug and test tag management and analytics implementations, displaying changes in an easy-to-read format. It supports multiple data layers and GTM containers, as well as tags from Google Analytics, Adobe Analytics, and Floodlight. It also offers an optional blocking feature to prevent data pollution.
Average rating: 4.6 (by 78 users).
Chrome extension downloads: 100,000+
Tag Assistant Legacy (by Google) 
Google Tag Assistant helps to troubleshoot the installation of various Google tags including Google Analytics, Google Tag Manager and more.
Tag Assistant is a Chrome extension that assists with the installation of Google tags, such as Google Analytics, Adwords Conversion Tracking, and Google Tag Manager, by verifying their presence on a page, reporting errors, and suggesting improvements.
Additionally, Tag Assistant Recording allows users to record a typical user flow to and through their website to validate, diagnose, and troubleshoot issues with their Google Analytics implementation.
Average rating: 4.1 (by 1153 users).
Chrome extension downloads: 2,000,000+
Tag Assistant Companion 
The Tag Assistant Companion extension works with Tag Assistant to help troubleshoot installation of gtag.js and Google Tag Manager.
The Tag Assistant Companion extension works with Tag Assistant to help troubleshoot installation of gtag.js and Google Tag Manager. When the Chrome extension is present, it enables additional features for Tag Assistant including debugging iframes and debugging multiple windows from the same debug session.
Average rating: 2.6 (by 25 users).
Chrome extension downloads: 400,000+
Waaila Tracking Validator 
Waaila Tracking Validator is a troubleshooting tool that helps you validate and test your analytics implementation.
Waaila is a browser extension that automates the validation of analytics implementation, allowing users to inspect and compare data layer content with a custom JSON schema, highlighting errors for immediate detection. It also offers features such as merged data layer displaying, viewing events that occurred before redirection, and enabling Google Analytics 4 debugging.
Average rating: 5 (by 6 users).
Chrome extension downloads: 138
Adswerve – dataLayer Inspector+ 
DataLayer Tools for Digital Analysts
The Adswerve dataLayer Inspector+ is a tool kit of utilities for digital analysts, allowing them to monitor and modify Google Analytics activity, evaluate dataLayer pushes, insert additional resources, and block scripts from loading. It contains GTM injector too.
Average rating: 4.7 (by 40 users).
Chrome extension downloads: 60,000+
GTM Copy Paste 
Copy your Tags, Triggers and Variables and Paste them into any other account
This Chrome extension allows users to easily copy and paste Tags, Triggers, and Variables from one Google Tag Manager account to another, with the items being uploaded through the GTM API. It is not currently possible to copy Built-In Variables, Folders, and Custom Templates.
Average rating: 4.4 (by 41 users).
Chrome extension downloads: 10,000+
Pixel Helpers for marketing tools
Meta (Facebook) Pixel Helper 
The Meta Pixel Helper is a troubleshooting tool that helps you validate your pixel implementation.
The Meta Pixel Helper (formerly Facebook Pixel Helper) is a troubleshooting tool that provides real-time feedback on the implementation of conversion or Facebook pixels, displaying a number indicating the number of pixel events and a detailed overview of the page’s pixels.
Average rating: 4.1 (by 1093 users).
Chrome extension downloads: 2,000,000+
Twitter Pixel Helper 
Displays an icon if there is a Twitter website tag on a given page
The Twitter Pixel Helper is a Chrome extension that helps advertisers verify their Twitter website tag implementation by providing real-time feedback on the website tags that were fired and any possible implementation mistakes.
Average rating: 3.4 (by 18 users).
Chrome extension downloads: 50,000+
TikTok Pixel Helper 
TikTok Pixel Helper is a Chrome extension that provides assistance with verifying and troubleshooting pixel installation, as well as offering implementation recommendations and detailed diagnostics. The new version, TikTok Pixel Helper 2.0, provides direct access to relevant instruction guides to quickly solve common issues.
Average rating: 2.2 (by 61 users).
Chrome extension downloads: 300,000+
UET Tag Helper (by Microsoft Advertising) 
This extension helps to identify issues in Microsoft Advertising UET tags
This Chrome extension helps to identify issues in Microsoft Advertising UET tags, allowing users to see which tags are on a page, if conversion goals and Dynamic Remarketing lists have been set up correctly, and how to fix any encountered issues.
Average rating: 4.4 (by 23 users).
Chrome extension downloads: 90,000+
Website technology insights
BuiltWith Technology Profiler 
The BuiltWith browser extension allows users to easily discover the technologies used to build a website with a single click of the icon. BuiltWith is a website profiler tool that returns all the technologies it can detect on a page.
Average rating: 4.4 (by 400 users).
Chrome extension downloads: 300,000+
Wappalyzer – Technology profiler 
Identify web and marketing technologies .
Wappalyzer is a Chrome extension that can detect the technologies used on websites, such as programming languages, analytics, marketing tools, payment processors, CRM, CDN and more, with just a glance.
Average rating: 4.6 (by 1854 users).
Chrome extension downloads: 2,000,000+
Helpful Utilities
RestMan 
RESTMan is a browser extension that allows users to make HTTP requests and work with REST APIs over HTTP and HTTPS. It can be used by clicking on the extension icon, typing in a URL, choosing a method, and pressing “Send” or Ctrl+Enter. The response will display information about the response and the content.
Average rating: 4.7 (by 27 users).
Chrome extension downloads: 40,000+
Disable Content-Security-Policy 
Disable Content-Security-Policy for web application testing. When the icon is colored, CSP headers are disabled.
This Chrome extension allows users to temporarily disable the Content-Security-Policy header for a tab when testing third-party tags, though it should be used with caution as it disables features designed to protect against cross-site scripting.
Average rating: 3.7 (by 71 users).
Chrome extension downloads: 50,000+