The document discusses the complexities of custom Google Tag Manager (GTM) client templates and the challenges of replacing GA4 requests. It emphasizes the differences between GA4 and SSGTM requests, outlining various client tasks and potential use cases for custom clients. Tips for managing server-side custom clients and understanding the importance of response handling and trigger conditions are also provided.

1. Custom GTM Client Templates
(and why it is so hard to replace gtag / GA4)
Markus Baersch

2. What is a client in ssGTM?

3. ssGTM
“Receiving Thingies” in ssGTM
Events
key1: value1
key2: value2
key3: value3
…
Tags
Tag
Tag
Tag
Clients
Client
Clien
t
Client
/endpoint?param1=x&param2=y…

4. Common client tasks
Respond
3
● process (response) data from tags
● send server response (usually)
“Decouple” tags
from raw requests
2
● create event data
● run container to trigger tags
Receive requests
1
● different endpoints
● or same endpoint and different
priority (first to “claim” wins)

6. How “clients” got their name And finally: how
should we call
those receiving
thingies? worker
!
listener
!
endpoint
!
collector!
sensor!
receiver
!
event
processor!
client
💩
Senior dev had dark mode and could speak in Courier
New. So unfortunately, he took the jackpot… :(

7. Clients in ssGTM

8. Clients in ssGTM

9. Event Data: What tags need to work

10. Comparing GA4 requests

11. Q: Will a GA4 request be the same after passing ssGTM?
https://www.diffchecker.com/R1z4xmC9/
A: No

12. Q: What if GA4 adds new parameters?

13. Everything ends up in X-Files Fields ;)

14. Building client templates

15. Building a custom client is easy!
https://developers.google.com/tag-platform/tag-manager/server-side/api

16. Building a custom client is easy!

17. Forwarding all parameters as event data? Easy!

18. data.example.com/param_demo?
event_name=my_event&val1=1&foo=bar&value=42
&currency=EUR&item_id=2&item_name=widget

19. Custom client use cases
Analytics / Data
Snowplow
Piwik PRO
…
Proxy
Tagless Re
quest Prox
y
APIs
“Cloud
Functions”
Preflight Requ
ests
Alternative
(GA4)
clients
Serve
resources
Static or
dynamic

20. GA4 requests / client alternatives?

21. Building a custom GA4 client is (still) easy!

22. Replacing GA4 requests is not easy
GA4 Measurement
Protocol
Needs help by a web
session and drops weights
on own foot
Universal Analytics
Measurement
Protocol
Goes all the way

23. Replacing GA4 requests is not easy
● browser controls everything!
○ e.g. start, count, end of session
● parameters constantly change!
● Consent Mode
-> running GA4 on a non-GA4 request stream is
hard!

24. GA4 event data…

25. … is quite different

26. Options
● live with some constraints
● do not expect data suitable for advertising
● mimic gtag in the browser and use GA4 client
● use alternatives like walker OS, Stape data
tag
● do not use GA4 at all ;)
-> use custom clients for other tools or tasks!

27. Example: walker.js in, Piwik PRO out

28. Example: walker.js in, Piwik PRO out

29. Server-Side
Custom client tips
Good to know:
➔ always return a response (there
is more than a status code)
➔ running the container is
optional
➔ clients can use the same APIs as
tags
➔ requests can contain multiple
events

30. Server-Side
Custom client tips
When more clients are used:
➔ check your trigger conditions
➔ “all events” or “all pages”
triggers are no longer your
friend
➔ use transformations whenever
clients and / or tags do not
allow event redaction

31. Done ;)

32. Thank you! :)
markus-baersch.de/
slideshare
markus-baersch.de/
podcast
markus-baersch.de/
youtube

33. Build!
markus-baersch.de/gtmb
ook