Failed to serialize XContent of field field – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 6.8-8.9

Briefly, this error occurs when Elasticsearch is unable to serialize the content of a specific field during the indexing process. This could be due to incompatible data types or malformed data. To resolve this issue, you can check the data type of the field and ensure it matches with the Elasticsearch mapping. If the data is malformed, you need to clean it before indexing. Also, ensure that the field is not empty or null as Elasticsearch might fail to serialize such fields.

This guide will help you check for common problems that cause the log ” failed to serialize XContent of field [” + field + “] ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: admin, mapping, indices.

Log Context

Log “failed to serialize XContent of field [” + field + “]” class name is We extracted the following from Elasticsearch source code for those seeking an in-depth context :

 includeDefaults ? includeDefaultsParams : ToXContent.EMPTY_PARAMS;
 fieldMappings.put(field; new FieldMappingMetadata(; bytes));
 } catch (IOException e) {
 throw new ElasticsearchException("failed to serialize XContent of field [" + field + "]"; e);


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