Referrer: the header that says where a click came from

The referrer is the address of the page a visitor was on when they clicked, sent by the browser in the Referer header — misspelled in the 1996 specification and never corrected.

Why it is so often missing

Native apps generally send nothing. A tap from Instagram, WhatsApp, Slack, a mail client or a PDF reader usually arrives with no referrer at all. Browsers trim what they do send: the common default is to send only the origin cross-site, so you learn the visitor came from google.com but never which query. Going from an HTTPS page to an HTTP one strips it entirely, and a page can suppress it with a Referrer-Policy of its own.

The result is that a large share of honest, human traffic is unattributable by header alone. Reading "direct" as "typed the URL in" is the mistake almost everyone makes.

How gc.mw records it

The header is parsed to a hostname, lowercased, with www., l. and m. prefixes stripped so m.facebook.com and l.instagram.com land in the same row as facebook.com. The host is then matched against a rules list that gives it a label and a type: search, social, email, ads or referral. No referrer means direct. A visit that arrived through a QR code is typed qr before the header is even consulted, because the QR image encodes the short link with a marker we add.

You get both views: the type breakdown for the shape of a campaign, and the host breakdown when you need to know which publication actually sent people. On the redirect itself we set Referrer-Policy: no-referrer-when-downgrade, the browser default, so we neither add nor remove information on the way to your destination.

What to use instead

Referrer data is a fallback. The reliable version is a distinct link per placement, or UTM values stored on the link — both are yours, and neither depends on a header the visitor's software may decline to send.

Example

A launch post drives 1,400 clicks. The referrer report shows 61% direct, 22% t.co, 9% linkedin.com. Nearly all the direct traffic was the Instagram story, which we know only because that story used its own code — gc.mw/lnch-ig — rather than the shared one.

Give each placement its own tagged URL with the UTM builder.