---
title: "Combined Log Format"
description: "The Combined Log Format is an extension of the Common Log Format that adds the referrer URL and user-agent string to each access log entry."
category: "Server Log Analysis"
date: "2026-03-05"
url: "https://getbeast.io/glossary/combined-log-format/"
type: "glossary"
---

# Combined Log Format

**Category:** Server Log Analysis | **Updated:** 2026-03-05

The Combined Log Format is an extension of the Common Log Format that adds the referrer URL and user-agent string to each access log entry.

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## What Is the Combined Log Format?

The Combined Log Format (CLF+) is the most widely used access log format for Apache and Nginx web servers. It extends the Common Log Format by appending two additional fields: the HTTP Referer header and the User-Agent header. A typical line looks like: `192.168.1.1 - - [10/Oct/2025:13:55:36 +0000] "GET /page HTTP/1.1" 200 2326 "https://google.com" "Mozilla/5.0 ..."`

## Why It Matters for SEO

The Combined Log Format is the **gold standard for SEO log analysis** because it includes the user-agent string (essential for identifying crawlers) and the referrer (essential for understanding traffic sources). Without the user-agent field, you cannot distinguish Googlebot from regular users. Without the referrer, you cannot track which pages link to which resources.

## How to Configure It

In Nginx, set `access_log /var/log/nginx/access.log combined;` in your server block. In Apache, use `LogFormat "%h %l %u %t "%r" %>s %b "%{Referer}i" "%{User-Agent}i"" combined`. Most servers use this format by default. [LogBeast](/logbeast/) natively supports Combined Log Format with auto-detection.

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## Related Terms

- [Common Log Format](/glossary/common-log-format/)
- [W3C Log Format](/glossary/w3c-log-format/)
- [Access Log](/glossary/access-log/)
- [Log Parsing](/glossary/log-parsing/)
- [User-Agent String](/glossary/user-agent-string/)

## Further Reading

- [Understanding Server Log Formats](/blog/log-formats/)

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*Part of the [GetBeast SEO Glossary](/glossary/). Visit [GetBeast.io](https://getbeast.io) for professional SEO and log analysis tools.*