# Date stream can not be created with uppercase name?

**URL:** <https://discuss.elastic.co/t/date-stream-can-not-be-created-with-uppercase-name/360034>\
**Category:** Elasticsearch\
**Created:** [May 23, 2024, 4:05am UTC](https://discuss.elastic.co/t/date-stream-can-not-be-created-with-uppercase-name/360034 "2024-05-23T04:05:12Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![liurui](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/liurui/32/99305_2.png) [@liurui](https://discuss.elastic.co/u/liurui)\
**Post date:** [May 23, 2024, 4:05am UTC](https://discuss.elastic.co/t/date-stream-can-not-be-created-with-uppercase-name/360034/1 "2024-05-23T04:05:12Z")

</div>

Why can't date stream names contain uppercase letters?

```auto
PUT _data_stream/Log

# response
{
  "error" : {
    "root_cause" : [
      {
        "type" : "illegal_argument_exception",
        "reason" : "data_stream [Log] must be lowercase"
      }
    ],
    "type" : "illegal_argument_exception",
    "reason" : "data_stream [Log] must be lowercase"
  },
  "status" : 400
}

```

---

<div class="post-metadata">

**Author:** ![yago82](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/yago82/32/97755_2.png) [@yago82](https://discuss.elastic.co/u/yago82)\
**Post date:** [May 23, 2024, 7:25am UTC](https://discuss.elastic.co/t/date-stream-can-not-be-created-with-uppercase-name/360034/2 "2024-05-23T07:25:57Z")

</div>

> [@liurui](#):
>
> Why can't date stream names contain uppercase letters?
> 
> ```auto
> PUT _data_stream/Log
> 
> # response
> {
> "error" : {
> "root_cause" : [
> {
> "type" : "illegal_argument_exception",
> "reason" : "data_stream [Log] must be lowercase"
> }
> ],
> "type" : "illegal_argument_exception",
> "reason" : "data_stream [Log] must be lowercase"
> },
> "status" : 400
> }
> 
> ```

Hi,

The requirement for data stream names to be lowercase is a design decision made by Elasticsearch. This is to ensure consistency and to avoid potential issues with case sensitivity across different systems and platforms.

Regards