# Mutate filter replace - please clarify the documentation

**URL:** <https://discuss.elastic.co/t/mutate-filter-replace-please-clarify-the-documentation/143700>\
**Category:** Logstash\
**Created:** [August 9, 2018, 1:08pm UTC](https://discuss.elastic.co/t/mutate-filter-replace-please-clarify-the-documentation/143700 "2018-08-09T13:08:23Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![JPelastic](https://avatars.discourse-cdn.com/v4/letter/j/9e8a1a/32.png) [@JPelastic](https://discuss.elastic.co/u/JPelastic)\
**Post date:** [August 9, 2018, 1:08pm UTC](https://discuss.elastic.co/t/mutate-filter-replace-please-clarify-the-documentation/143700/1 "2018-08-09T13:08:23Z")

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This is the info given in the docs:

> Replace a field with a new value. The new value can include `%{foo}` strings to help you build a new value from other parts of the event.

This first sentence is highly ambiguous.

Does this either means:

1. Replace the value of a field with a new value
2. Change the name of a field into another name (i.e. "a new value")

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**Author:** ![magnusbaeck](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/magnusbaeck/32/44943_2.png) [@magnusbaeck](https://discuss.elastic.co/u/magnusbaeck)\
**Post date:** [August 9, 2018, 1:16pm UTC](https://discuss.elastic.co/t/mutate-filter-replace-please-clarify-the-documentation/143700/2 "2018-08-09T13:16:30Z")

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> 1. Replace the value of a field with a new value

Yes.

Feel free to submit a patch to the documentation.

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<div class="post-metadata">

**Author:** ![JPelastic](https://avatars.discourse-cdn.com/v4/letter/j/9e8a1a/32.png) [@JPelastic](https://discuss.elastic.co/u/JPelastic)\
**Post date:** [August 9, 2018, 1:18pm UTC](https://discuss.elastic.co/t/mutate-filter-replace-please-clarify-the-documentation/143700/3 "2018-08-09T13:18:19Z")

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I will when I find out how (I will look 😉 )

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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:** [September 6, 2018, 1:18pm UTC](https://discuss.elastic.co/t/mutate-filter-replace-please-clarify-the-documentation/143700/4 "2018-09-06T13:18:27Z")

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