#Attribution and channels

#Attribution keys

3x stores 13 campaign parameters per session, taken from the URL of the entry pageview:

• Click ids are kept complete (up to 256 characters) because conversion uploads need them.
• UTM values are cut to 100 characters. Values that look like e-mail addresses are dropped; UTM values that look like phone numbers are dropped. Pure digit ids stay.
• Projects can redact values with regular expressions (for example post-XXXX → post-:code for personalized letters).
• attr_from records where the attribution came from: url, stored or none.

#First touch across sessions

With consent and tracking.firstTouch.enabled, the SDK stores the first attribution it sees in localStorage (<prefix>attribution) and uses it for later sessions without URL attribution (attr_from = stored). Before consent nothing is written, so first touch is per session only.

#Campaign changes split sessions

A pageview whose URL attribution differs from the session's entry attribution on any key starts a new session, so every session belongs to exactly one campaign.

#Channels

The channel of a session is derived from its entry attribution and referrer host. Rules are versioned per project: a published version never changes, so historic data stays comparable.

Rules of version 2, first match wins:

1. Click ids: gclid/gbraid/wbraid → google_ads; fbclid → meta; li_fat_id → linkedin; msclkid → bing; ttclid → tiktok.
2. utm_source: AI assistants (chatgpt, perplexity, claude, gemini, copilot, …) → ai_assistant; e-mail media or newsletter tools → email; google/adwords/googleads → google_ads when the medium is paid (cpc, ppc, paid, sem, display, pmax, youtube, …) or the source is not plain google, else google_organic; linkedin/li/lnkd → linkedin; facebook/instagram/fb/ig/meta → meta; bing/microsoft → bing; tiktok/tt → tiktok; other search engines → search_other; other social networks → social_other; any other source → other.
3. Referrer host: none or own host → direct; AI assistant hosts → ai_assistant; webmail → email; google.* → google_organic; bing.com/msn.com → bing; LinkedIn, Meta, TikTok hosts → their channel; other search engines and social networks → search_other / social_other; anything else → referral.

Changing a project's version affects new sessions only.

#Paid vs organic

The filter traffic=paid selects sessions with any ad click id or a paid utm_medium (cpc, ppc, paid, paid_social, display, cpm, …); traffic=organic selects the rest. This is the "ads vs all" split used on the leads and funnels pages.

#Ad entities

Beyond channels, sessions are matched to the exact campaign, ad set and ad that brought them when ad accounts are connected – see Matching sessions to ads. The recommended UTM templates make those matches exact.