Unknown Similarity type value for field name – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 6.8-8.9

Briefly, this error occurs when Elasticsearch encounters an unknown similarity type for a specific field. The similarity type is used to define how Elasticsearch should score matching documents. If the type is not recognized, this error is thrown. To resolve this issue, you can either use a predefined similarity type like “BM25” or “classic”, or define your own custom similarity in the index settings. Make sure to use the correct syntax and spelling when specifying the similarity type.

This guide will help you check for common problems that cause the log ” Unknown Similarity type [” + value + “] for field [” + name + “] ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: index.

Log Context

Log “Unknown Similarity type [” + value + “] for field [” + name + “]” class name is TypeParsers.java. We extracted the following from Elasticsearch source code for those seeking an in-depth context :

 if (value == null) {
 return null;    // use default
 SimilarityProvider similarityProvider = parserContext.getSimilarity(value.toString());
 if (similarityProvider == null) {
 throw new MapperParsingException("Unknown Similarity type [" + value + "] for field [" + name + "]");
 return similarityProvider;


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