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User ID Power-Up

A stable, anonymous visitor ID sent to your server container as a request header, as a fallback when cookies are lost.

2 min readUpdated Nov 9, 2026Taglinko docs
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Cookies get blocked, shortened and deleted, so the same visitor can look like a new one on every visit. The User ID power-up gives your server container another way to recognise a returning visitor: an anonymous ID calculated from the request itself.

How the ID is made

Taglinko takes the visitor's IP address, user-agent and the hostname of the request, adds the secret salt of your container, and hashes them (SHA-256). The same visitor on the same network and browser gets the same ID. Nothing is stored: it is calculated for each request, in front of your container, and put in the X-Taglinko-User-Id request header. Taglinko sets that header on every request, so a visitor cannot send their own.

Set it up

  1. Open your container, go to Power-Ups and turn on User ID. The container restarts once.
  2. In your server container go to Variables, create a new variable of type Request Header and set the header name to X-Taglinko-User-Id. There is nothing to download or import.
  3. Use the variable where you need an ID: as user_id or external_id on your tags, or as a key in the Data Store.
  4. To check it, open Preview and select an incoming request: the header is in its list.

The salt belongs to one container: the same visitor gets a different ID in another container, so IDs cannot be matched across customers. The salt stays unchanged while the power-up exists, so the IDs stay the same.

Without the header

If you prefer to calculate the ID inside the container, the power-up also offers a Taglinko User ID variable template (download, import, paste the salt). It gives the same ID.

What to expect

  • It is a fallback, not a replacement for a first-party cookie (see Cookie Keeper). The ID changes when the visitor's IP address, browser or the hostname changes, for example when a phone moves from Wi-Fi to mobile data.
  • Several people behind one office network with the same browser can share an ID.
  • To measure the effect, compare your remarketing audience size and returning-user numbers for 2 to 4 weeks before and after.

Still stuck?

Open a support ticket from your dashboard and include the container name.

Contact support