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When a new member signs up, Outpost automatically captures UTM parameters and referral values from the URL and applies them as member labels. This lets you see exactly which campaigns, channels, and creatives are driving signups — directly in your member list and Ghost. Attribution fires on any signup that flows through Outpost, including Auto Display CTAs, paywalls, and Gated Downloads.

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Parameters captured

URL parameterLabel appliedExample
utm_source, source, or refsource:[value]source:facebook
utm_mediummedium:[value]medium:email
utm_campaigncampaign:[value]campaign:spring-sale-2026
utm_contentcontent:[value]content:hero-banner
utm_termterm:[value]term:paid-subscribers
Values are stored in the reader’s browser session (sessionStorage, which lasts until the tab or browser is closed) and applied to their member record at the moment they sign up. If a reader visits from a UTM link, browses for a while, and then subscribes — the attribution is still captured. If they later arrive via a different UTM-tagged link in the same session, the newer values replace the older ones, so attribution reflects the last-clicked link.

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How it works

Outpost reads these parameters from the URL when a page loads and holds them in the browser session. When the reader submits any CTA form (In-Post, Popup, Slide-Up, Homepage, Metered Wall, or Gated Download), the stored values are sent along and applied as labels.

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Examples

Newsletter campaign: 
https://yoursite.com/welcome?utm_source=newsletter&utm_campaign=may-newsletter&utm_content=cta-button
Labels applied on signup: source:newsletter, campaign:may-newsletter, content:cta-button
Social media post: 
https://yoursite.com/big-story?utm_source=bluesky&utm_campaign=big-story-launch
Labels applied: source:bluesky, campaign:big-story-launch
Referral link from another publication: 
https://yoursite.com/?ref=newsletter-partner
Label applied: source:newsletter-partner
Paid ad with full attribution: 
https://yoursite.com/?utm_source=facebook&utm_campaign=fall-2026&utm_content=video-ad&utm_term=annual-subscribers
Labels applied: source:facebook, campaign:fall-2026, content:video-ad, term:annual-subscribers
Outpost promotion link (automatically tracked): Promotion URLs like https://yoursite.com/promo/abc123 already have built-in Outpost tracking. You can append UTM parameters to add channel context on top: 
https://yoursite.com/promo/abc123?utm_source=podcast&utm_campaign=sponsorship-june

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Using attribution labels

Once applied, these labels work like any other Outpost label:
  • Filter your member list — find all members who signed up from a specific campaign (campaign:spring-sale-2026)
  • Trigger email flows — start a welcome sequence when source:newsletter-partner is added
  • Exclude from automations — skip paid acquisition members from certain flows
  • Measure channel ROI — compare free-to-paid conversion rates across sources using label-based segments
Parameters are captured on any page load where they appear in the URL, and newer values overwrite older ones within the same browser session (last-touch attribution). Labels are only applied at the moment of signup — they cannot be retroactively added to existing members unless you do so manually.

Labels

How member labels work and where they apply

Auto Display CTAs

The conversion widgets that trigger attribution on signup

CTA Dashboard

View signup and conversion analytics across all your CTAs

Analytics

Trace signups and conversions back to campaigns and channels