# Want to Understand Agent Filter **URL:** \ **Category:** Logstash\ **Created:** [September 6, 2015, 6:02pm UTC](https://discuss.elastic.co/t/want-to-understand-agent-filter/28749 "2015-09-06T18:02:33Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![bhutchinson](https://avatars.discourse-cdn.com/v4/letter/b/2acd7d/32.png) [@bhutchinson](https://discuss.elastic.co/u/bhutchinson)\ **Post date:** [September 6, 2015, 6:02pm UTC](https://discuss.elastic.co/t/want-to-understand-agent-filter/28749/1 "2015-09-06T18:02:33Z")
What is the best way to understand what fields the **agent filter** creates and what values are actually stored in the fields? **Example Questions** The agent filter creates an field named "os" and a field named "os\_name". What is the difference between these fields? The agent filter creates a device field. How can I understand the different values that are populated in the device field? The device field gets populated with values of "Other" or "Spider" ---
**Author:** ![warkolm](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/warkolm/32/39224_2.png) [@warkolm](https://discuss.elastic.co/u/warkolm)\ **Post date:** [September 6, 2015, 9:36pm UTC](https://discuss.elastic.co/t/want-to-understand-agent-filter/28749/2 "2015-09-06T21:36:46Z")
I can't directly help, but this has been raised before and there is an GH issue to improve the documentation - [Does the useragent filter produce two apparently identical os fields?](https://discuss.elastic.co/t/does-the-useragent-filter-produce-two-apparently-identical-os-fields/27270) ---
**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\ **Post date:** [July 6, 2017, 5:29am UTC](https://discuss.elastic.co/t/want-to-understand-agent-filter/28749/3 "2017-07-06T05:29:52Z")
Closed on July 6, 2017, 5:29am UTC