Click ID

When a visitor clicks an affiliate link, the network logs the click and assigns it a unique click ID. The ID is appended to the URL that lands on the merchant's site. If the merchant captures it and posts it back to the network when a sale completes, the network can attribute the conversion even when the browser cookie has been blocked, cleared, or expired. The click ID is the backbone of modern server-to-server (S2S) attribution.

Click ID parameter names by network. Impact uses irclickid. CJ (Commission Junction) uses cjevent. Awin embeds a hash inside the redirect URL. ShareASale uses aff_id-paired click hashes. Rakuten and Partnerize have proprietary names. The exact parameter is irrelevant to you as a publisher; it is the integration handshake between the network and the merchant. What matters is that the network puts the click ID into the landing URL automatically.

How the S2S postback flow works. Step one: visitor clicks your affiliate URL; the network records the click and generates a click ID (irclickid=abc123). Step two: the network redirects to the merchant with the click ID appended (merchant.com/product?irclickid=abc123). Step three: the merchant captures irclickid from the URL, stores it in a first-party cookie or session. Step four: when the visitor completes a purchase, the merchant fires a server-side request to the network: "conversion for click abc123, sale value €99." The network then credits the publisher tied to that click. No third-party cookie involved.

Why click IDs matter increasingly. Browser cookie support has been eroding for years. Safari has blocked third-party cookies by default since 2020 under Intelligent Tracking Prevention. Firefox blocks them by default since 2019. Chrome's gradual phase-out reached most users by 2025. S2S via click ID is the post-cookie fallback. For creators, this means networks with mature S2S support (Impact, CJ, Awin, Partnerize) preserve attribution more reliably than networks that still rely primarily on browser cookies (older ShareASale integrations, Amazon Associates for non-logged-in shoppers).

Click ID versus <a href="/glossary/sub-id" class="font-medium text-ab-violet underline decoration-ab-violet/30 underline-offset-4 transition-colors hover:decoration-ab-violet">sub-ID</a> versus cookie. Three separate mechanisms. The cookie identifies the visitor for the duration of the cookie window (purely client-side). The click ID identifies the specific click and enables server-to-server matching when the cookie fails. The sub-ID is your own label that describes the placement. The click ID is the network's; the sub-ID is yours; the cookie is the browser's.

Click IDs are visible in the URL. Visitors see them in the address bar after they click through. The values are opaque hashes (no PII), so privacy regulations like GDPR generally treat them as legitimate functional identifiers rather than tracking cookies, but you should still mention them in your privacy disclosures if you operate within the EU.

Forensic value. If a conversion that should have been credited never appears in your reports, the click ID is the breadcrumb. Catch the click ID at the moment of the click (browser dev tools, network log, or your own redirect server), keep it, and you can contact the affiliate network with the exact ID and ask them to look up what happened. Without the click ID, "I think I sent traffic last Tuesday" is unverifiable.