# Removing prefix from field names
**URL:** https://discuss.elastic.co/t/removing-prefix-from-field-names/339674
**Category:** Logstash
**Created:** [July 31, 2023, 10:12am UTC](https://discuss.elastic.co/t/removing-prefix-from-field-names/339674 "2023-07-31T10:12:34Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@VirusProtect](https://discuss.elastic.co/u/VirusProtect)
#### Post date: [July 31, 2023, 10:12am UTC](https://discuss.elastic.co/t/removing-prefix-from-field-names/339674/1 "2023-07-31T10:12:34Z")
Hi, I have fields in Kibana such as `fw.ip`, `fw.name`, `fw.test.old`, and so on. I am trying to remove the "fw" prefix from all these fields using a Ruby filter in Logstash. Here's the code I'm using:
```auto
ruby {
code => "
event.to_hash.keys.each do |key|
if key.start_with?('fw.')
new_key = key.sub('fw.', '')
event.set(new_key, event.get(key))
event.remove(key)
end
end
"
}
```
Unfortunately, this is not working. How can I remove the prefix "fw." from all fields using Ruby?
Thank you!
---
### Author:  [@carly.richmond](https://discuss.elastic.co/u/carly.richmond)
#### Post date: [July 31, 2023, 10:20am UTC](https://discuss.elastic.co/t/removing-prefix-from-field-names/339674/2 "2023-07-31T10:20:28Z")
Hi @VirusProtect,
Are you getting a particular error from your Ruby code?
---
### Author:  [@leandrojmp](https://discuss.elastic.co/u/leandrojmp)
#### Post date: [July 31, 2023, 1:39pm UTC](https://discuss.elastic.co/t/removing-prefix-from-field-names/339674/3 "2023-07-31T13:39:33Z")
> [@VirusProtect](#):
>
> Hi, I have fields in Kibana such as `fw.ip`, `fw.name`, `fw.test.old`, and so on.
Is this a prefix or an object named `fw` with nested field? For example
This is a field with a dot in the name and the `fw` as a prefix
```auto
"{ "fw.ip": "8.8.8.8" }
```
And this is json object named `fw` with a nested field named `ip`
```auto
"{ "fw": { "ip": "8.8.8.8" } }
```
In kibana they will look the same in discover, you will only be able to know if it is a field with a prefix or a json object looking at the json tabe for the document.
Can you provide a sample of how your document looks like in Kibana looking at the json tab in the discover?
---
### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [August 28, 2023, 1:40pm UTC](https://discuss.elastic.co/t/removing-prefix-from-field-names/339674/4 "2023-08-28T13:40:21Z")
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