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Splitting is generally recommended for long Documents as it makes the Retriever's job easier and speeds up Question Answering. For suggestions on how best to split your documents, see [Optimization](🔗).

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**Position in a Pipeline**As early in an indexing Pipeline as possible but after File Converters and Crawlers


To start working with code examples, have a look at the [preprocessing tutorial](🔗). For ideas on what you can do at indexing time, see [advanced indexing tutorial](🔗).

## Usage

To initialize `PreProcessor`, run:

clean_empty_linesboolNormalizes 3 or more consecutive empty lines to be just a two empty lines.
clean_whitespaceboolRemoves any whitespace at the beginning or end of each line in the text.
clean_header_footerboolRemoves any long header or footer texts that are repeated on each page.
split_bystringDetermines what unit the document is split by. Choose from `'word'`, `'sentence'` or `'passage'`.
split_lengthintSets a maximum number of `'word'`, `'sentence'` or `'passage'` units per output document
split_respect_sentence_boundaryboolEnsures that document boundaries do not fall in the middle of sentences
split_overlapintSets the amount of overlap between two adjacent documents after a split. Setting this to a positive number essentially enables the sliding window approach.

To run the `PreProcessor` by itself, run:

To use `PreProcessor` in a pipeline, run:

## Document Format

When you are not using an indexing Pipeline, the PreProcessor can take either `Document` objects (recommended) as input or plain dictionaries. To learn more about the `Document` class, see [Documents, Answers, and Labels](🔗).