# Access log

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/)

An **access log** is the file in which a web server records each request it handles, one line per request. A line typically shows when the request came in, which URL was requested, which HTTP status code the server returned, and who sent it.

## What does an entry contain?

The operator decides the fields in the server configuration. In the widely used Combined Log Format, an entry holds the client IP address, a timestamp, the request line (method, path, protocol), the status code, the response size in bytes, the referer and the user agent. Apache writes this to `logs/access_log` by default, nginx to `logs/access.log`, and nginx uses the combined format unless told otherwise.

IP addresses can be personal data (CJEU, judgment of 19 October 2016, C-582/14, Breyer).

This is not legal advice.

## Why do SEOs care?

The user agent field shows whether a request came from a search engine or AI bot. Together with the URL and status code, that tells you which pages a bot fetched and how the server answered. A user agent can be faked, so Google documents a check of the IP address through reverse and forward DNS lookups and published IP ranges. Apache also warns that log lines can contain client-supplied text without escaping, so write access to the log directory should be restricted.

## Example

```txt
66.249.66.1 - - [10/Oct/2026:13:55:36 +0000] "GET /products/ HTTP/1.1" 200 2326 "-" "Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)"
```

This invented line shows a request for `/products/` that the server answered with status 200.

*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

- [Log file](https://seo-geo-glossary.com/en/glossary/log-file/index.md)
- [Log file analysis](https://seo-geo-glossary.com/en/glossary/log-file-analysis/index.md)
- [Combined Log Format](https://seo-geo-glossary.com/en/glossary/combined-log-format/index.md)

## Sources

- [Log Files - Apache HTTP Server 2.4](https://httpd.apache.org/docs/2.4/logs.html)
- [Module ngx_http_log_module - nginx](https://nginx.org/en/docs/http/ngx_http_log_module.html)
- [Verifying Googlebot and other Google crawlers - Google Search Central](https://developers.google.com/crawling/docs/crawlers-fetchers/verify-google-requests)
- [CJEU, judgment of 19 October 2016, C-582/14 (Breyer) – EUR-Lex](https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:62014CJ0582)

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