Those annoying tracking pixels mess up my a11y scan. This is an attempt to add alt, role, and aria attributes to these guys. Uses MutationObserver to immediately update the img tags when they are added to the DOM by the tracking snippet's action.

a11y-tracking-pixels.js

// early in the head as possible
var observer = new MutationObserver(function(mutations){
    for (var i=0; i < mutations.length; i++){
        for (var j=0; j < mutations[i].addedNodes.length; j++){
            checkNode(mutations[i].addedNodes[j]);
        }
    }
});
  
observer.observe(document.documentElement, {
    childList: true,
    subtree: true
});

checkNode = function(addedNode) {
    if (addedNode.nodeType === 1 && addedNode.tagName === 'IMG'){
        var isTracker = false;

        // add your expected tracking pixel domains here
        if (addedNode.src.includes("pages01.net")){ isTracker = true; }
        if (addedNode.src.includes("bat.bing.com")){ isTracker = true; }
        if (addedNode.src.includes("apt.techtarget.com")){ isTracker = true; }

        if (isTracker){
            addedNode.setAttribute("alt", "");
            addedNode.setAttribute("role", "presentation");
            addedNode.setAttribute("aria", "hidden");
            console.log('alt text added to tracker img: ', addedNode)
        }      
    }
}

window.onload = (event) => {
    console.log('page is fully loaded');
    setTimeout(function() { console.log('disconnecting DOM observer...'); observer.disconnect(); }, 5000);
};