To make text fields searchable, Atlas Search creates indexes in Atlas. To control how the index sets search terms, like where to break up word groupings and whether to consider punctuation, specify an analyzer to use.

When creating Atlas Search index on a field, you can set how MongoDB transforms the field contents search terms. Atlas Search refers to this process as analysis. To control how MongoDB creates search terms, use a Atlas Search analyzer in the index definition. You may specify an analyzer when creating an index, executing a query, or both.

Atlas Search provides the following built-in analyzers:

Analyzer Description
Standard Uses the default analyzer for all Atlas Search indexes and queries.
Simple Divides text into searchable terms wherever it finds a non-letter character.
Whitespace Divides text into searchable terms wherever it finds a whitespace character.
Language Provides a set of language-specific text analyzers.
Keyword Indexes text fields as single terms.

You can also create your own custom analyzer.

If you don’t specify an analyzer, MongoDB uses the default standard analyzer.