What is a referrer?

The referrer is the address of the page a visitor was on before arriving at yours, sent by the browser in the HTTP Referer header, which analytics tools use to show where traffic comes from.

A request that came from a link on another site:

GET /pricing HTTP/1.1
Host: example.com
Referer: https://news.example.org/article/42

Why it is missing

Many visits arrive without one.

Typed or bookmarked

No page sent the visitor, so there is no referrer.

Apps and messengers

Links opened from native apps, email clients and chat apps often carry none.

Privacy settings

Browsers and extensions trim or strip referrers, and a Referrer-Policy can reduce them to the domain.

HTTPS to HTTP

Browsers don't send the referrer when moving from a secure page to an insecure one.

rel=noreferrer

Links can opt out of sending it.

Redirects

The referrer may be that of the redirecting page, not the original.

Spelling

The header is misspelled on purpose.

The HTTP header is Referer, with a single r, a typo in the original specification that stuck. The related policy header is spelled correctly: Referrer-Policy.

FAQ

Common questions

Why does traffic show as direct? +

Direct is analytics' bucket for visits with no referrer. Many of them come from apps and messages, not from people typing your address.

How can I get a reliable source? +

Tag links with UTM parameters, or give each placement its own short link so it can be counted separately.

Is the referrer a privacy risk? +

It can leak the address of the page a visitor was on, including query strings. A strict Referrer-Policy limits this.

Do short links see the referrer? +

Yes. A short link records the referrer of each click, which is shown in its statistics.