Who sets irclickid, and when
irclickid is not generated by the merchant's website. Impact's own redirect domain writes it into the URL the instant a shopper clicks a partner's affiliate link, before the browser ever reaches the merchant's site. By the time the landing page loads, the value is already sitting in the query string.
What it identifies
irclickid marks one click, not a shopper and not a whole campaign. Two clicks from the same person, on the same link, on the same day, produce two different irclickid values. Impact's own documentation treats it as a click ID: an opaque token pointing back to a single click-through event, nothing more.
It survives an ordinary redirect chain. It is case-sensitive, so do not lowercase or trim it. There is nothing to decode by eye.
How a click becomes a commission
When the shopper eventually buys, the merchant's confirmation page fires Impact's conversion tag. That tag reads irclickid, usually pulled from a cookie set when the shopper first landed, and sends it back to Impact's servers. Impact matches the token against the original click record, works out which partner sent the traffic, and only then releases a commission to that partner. Without a matching irclickid on the conversion event, the sale cannot be tied to any click, no matter where the traffic genuinely came from.
What changes if you strip it
A visitor notices nothing. The page loads and checkout completes the same either way. The publisher who sent the traffic is the one who pays for it: Impact can no longer match the eventual sale back to the click that produced it, so the commission never gets released, and the brand's own reporting tends to credit the sale to direct traffic instead of the partner who actually earned it.
That is why irclickid sits in the same family as cjevent and awc, rather than with simple tags like utm_source. Paste your own link into the link decoder to see irclickid pulled out on its own.