# Referrer

Category: [Log Files](https://seo-geo-glossary.com/en/glossary/category/log-files/) › [Log data & formats](https://seo-geo-glossary.com/en/glossary/category/log-files/log-data-formats/)

The **referrer** is the address of the page from which a visitor reached the current page. The browser sends it in the HTTP header `Referer`, so the target server learns where the request came from. MDN names analytics, logging and caching optimization as typical uses.

## How does it work?

When someone clicks a link, the browser can include the URL of the originating page in the header. Server logs and analytics tools then show which page referred the visit. If someone types an address or opens a bookmark, there is no originating page and therefore no referrer.

The header name is a historic misspelling. The specification spells it `Referer` with one r, while the concept and the `Referrer-Policy` header use two.

The header can contain origin, path and query string, but not the fragment or login data. Because URLs can hold sensitive information, RFC 9110 points to privacy risks and to policies that limit when the header is sent. The `Referrer-Policy` header controls how much is sent. It can be set as an HTTP header, with a meta tag or as an attribute on a single element. Without a setting, browsers use `strict-origin-when-cross-origin` according to MDN. Within the same origin the full URL is sent. To other origins only the origin is sent, and nothing is sent when the connection drops from HTTPS to HTTP.

## Example

```
Referer: https://www.example.com/guides/
```

```html
<meta name="referrer" content="origin">
```

With `origin` the browser only sends `https://www.example.com/`. On a single link, `rel="noreferrer"` switches the header off.

## Relevance for SEO

Analytics tools and the Combined Log Format use the referrer to assign visits to sources such as other websites or search engines. Stricter policies reduce how much detail arrives.

## Common mistakes

- **Mixing the spellings.** The request header is `Referer`, the policy header is `Referrer-Policy`. Server rules and log formats need the matching spelling.
- **Confusing `noreferrer` and `no-referrer`.** On a link it is `rel="noreferrer"` without a hyphen. In the meta tag and the header it is `no-referrer` with a hyphen (MDN).
- **Setting a strict policy without considering the effects.** With `no-referrer` the header is omitted entirely, and with `same-origin` it is missing for requests to other origins. Target pages and their analytics then see no source.
- **Treating a missing referrer as "direct".** Besides typed addresses and bookmarks, a policy can suppress the header too.

## FAQ

**What is an HTTP referrer?** The header that names the previous page of a request.

**Can the referrer be spoofed?** Yes. Like the user agent, clients can set it freely, so it is not proof of origin.

*Diagram: One log line, field by field.* Apache and nginx write the same fields in the same order in the “combined” format. IP addresses can be personal data (CJEU, judgment of 19 October 2016, C-582/14). Not legal advice.

## Related terms

- [Referral traffic](https://seo-geo-glossary.com/en/glossary/referral-traffic/index.md)
- [Direct traffic](https://seo-geo-glossary.com/en/glossary/direct-traffic/index.md)
- [Dark traffic](https://seo-geo-glossary.com/en/glossary/dark-traffic/index.md)
- [Combined Log Format](https://seo-geo-glossary.com/en/glossary/combined-log-format/index.md)
- [Access log](https://seo-geo-glossary.com/en/glossary/access-log/index.md)
- [User agent](https://seo-geo-glossary.com/en/glossary/user-agent/index.md)

## Sources

- [Referer header – MDN Web Docs](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Referer)
- [Referrer-Policy header – MDN Web Docs](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Referrer-Policy)
- [RFC 9110, section 10.1.3 Referer – IETF](https://www.rfc-editor.org/rfc/rfc9110.html#name-referer)
- [Referrer – Seobility Wiki (secondary)](https://www.seobility.net/en/wiki/Referrer)

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Last updated: October 8, 2026
URL: https://seo-geo-glossary.com/en/glossary/referrer/