# Using "\_" character

**URL:** <https://discuss.elastic.co/t/using---character/3199>\
**Category:** Elasticsearch\
**Created:** [August 9, 2010, 1:19pm UTC](https://discuss.elastic.co/t/using---character/3199 "2010-08-09T13:19:18Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![otisg](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/otisg/32/492_2.png) [@otisg](https://discuss.elastic.co/u/otisg)\
**Post date:** [August 9, 2010, 1:19pm UTC](https://discuss.elastic.co/t/using---character/3199/1 "2010-08-09T13:19:18Z")

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Hello,

Is there a general rule for when the "\_" character is used in JSON, in  
URLs, and other places?

e.g. \_script in JSON in [http://github.com/elasticsearch/elasticsearch/issues/293](http://github.com/elasticsearch/elasticsearch/issues/293)  
or \_source in JSON responses or \_all in URL, etc.

## Thanks, Otis

Sematext :: [http://sematext.com/](http://sematext.com/) :: Solr - Lucene - Nutch  
Lucene ecosystem search :: [http://search-lucene.com/](http://search-lucene.com/)

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**Author:** ![kimchy](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/kimchy/32/44952_2.png) [@kimchy](https://discuss.elastic.co/u/kimchy)\
**Post date:** [August 9, 2010, 2:19pm UTC](https://discuss.elastic.co/t/using---character/3199/2 "2010-08-09T14:19:54Z")

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The general rule is for "internal" fields / constructs, elasticsearch uses  
\_. For example, the \_source and \_type fields, and for \_score which is not  
really a field.

-shay.banon

On Mon, Aug 9, 2010 at 4:19 PM, Otis [otis.gospodnetic@gmail.com](mailto:otis.gospodnetic@gmail.com) wrote:

> Hello,
> 
> Is there a general rule for when the "\_" character is used in JSON, in  
> URLs, and other places?
> 
> e.g. \_script in JSON in  
> [Script based sort · Issue #293 · elastic/elasticsearch · GitHub](http://github.com/elasticsearch/elasticsearch/issues/293)  
> or \_source in JSON responses or \_all in URL, etc.
> 
> ## Thanks, Otis
> 
> Sematext :: [http://sematext.com/](http://sematext.com/) :: Solr - Lucene - Nutch  
> Lucene ecosystem search :: [http://search-lucene.com/](http://search-lucene.com/)

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**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, 4:21am UTC](https://discuss.elastic.co/t/using---character/3199/3 "2017-07-06T04:21:02Z")

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