Problem

After release GA4 (Google Analytics 4 or old named Google Analytics App + Web), the gtag web js client has some changes in timing about sending collecting data. Somehow, you will see it delayed the collecting request to GA server about 5 seconds after you trigger events.

The main reason is it queues all event in the window of 5000ms (5 seconds) then send them in 1 batch request to server. This behavior can reduce requests into the servers (reduce server load, round-trip connections and saving time to bootstrap the backend code)

What if the user close website before js client sends batch request ?

Looks like the js client has a backup way to flush the batch request before closing the website. It uses some browser events like ('focus', 'blur', 'pageshow', 'pagehide', 'visibilitychange' and 'beforeunload' event) and sendBeacon to achieve the backup plan :D

So it looks good, right ?

Yes ! Almost perfect !

What if I want to reduce the delayed timer or just send the request immediately ?

Yes, you can !! There are 1 way to do it. And, you have to proxy and patch the gtag source code in your backend.

REVERSE THE CODE

I reversed gtag source code then find out that 5 seconds equals 5000ms, and because it is minifying js, then I searched string 5E3

And this is it

Gtag Code

It calls setTimeout and function that flush all events after h = 5E3 ms

So what we need to replace is change the h variable to what duration we want

BACKEND SOLUTION

In this case, I use regex to replace (below example to change 5000ms to 250ms, a good number to wait few batch requests and sending them soon)

$gtag_url = 'https://www.googletagmanager.com/gtag/js?id=YOUR-ID';
$raw = file_get_contents($gtag_url);
$raw = preg_replace('/:(\w+)=5E3;this/', ':$1=5E3;$1=250;this', $raw, 1);

You can do it in your programming language :D

SERVERLESS SOLUTION

I use CloudFlare Worker (JS)

Demo my blog GA4 worker (&delay query params = 300ms) : https://ga-gtag-change-delay.khanhicetea.workers.dev/gtag/js?id=G-DEXLWK9G9D&delay=300

async function handleRequest(event) {
let url = new URL(event.request.url)
const { searchParams } = new URL(url)
// Get Delay number from query params, default = 250ms
const delay = searchParams.get('delay', 250)

url.hostname = 'www.googletagmanager.com'

let request = new Request(url, event.request)
let response = await fetch(request, {
cf: {
cacheTtl: 3600, // Cache on edge 1 hour
cacheEverything: true,
},
});
const body = await response.text()
const new_raw = body.replace(/:(\w+)=5E3;this/,':$1=5E3;$1='+delay+';this')

response = new Response(new_raw, response)
response.headers.set('Cache-Control', 'max-age=86400') // Cache on Browser 1 day

return response
}

addEventListener('fetch', (event) => {
return event.respondWith(handleRequest(event))
})

The reason I used RegEx, because the h variable can be changed name after Google server minify it in next time.

ENJOY !