---
title: Keyword search
description: Enable BM25 keyword search in AI Search to match documents containing exact query terms.
image: https://developers.cloudflare.com/dev-products-preview.png
---

> Documentation Index  
> Fetch the complete documentation index at: https://developers.cloudflare.com/ai-search/llms.txt  
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# Keyword search

Enable keyword search to match chunks that contain your query terms exactly. For an overview of search modes, refer to [Search modes](https://developers.cloudflare.com/ai-search/concepts/search-modes/).

## Enable keyword search

Set `index_method.keyword` to `true` when creating or updating an instance. You can use keyword search on its own or alongside vector search for [hybrid search](https://developers.cloudflare.com/ai-search/configuration/indexing/hybrid-search/).

| Field   | Type    | Default | Description                      |
| ------- | ------- | ------- | -------------------------------- |
| vector  | boolean | true    | Enable vector (semantic) search. |
| keyword | boolean | false   | Enable keyword (BM25) search.    |

At least one of `vector` or `keyword` must be `true`. Changing `index_method` triggers a full reindex of your content.

TypeScript

```
const instance = await env.AI_SEARCH.create({  id: "my-instance",  index_method: {    vector: false,    keyword: true,  },});
```

## Keyword tokenizer

The `keyword_tokenizer` field (inside `indexing_options`) controls how text is split into tokens. Changing this triggers a full reindex.

| Value   | Default | Description                                                                       |
| ------- | ------- | --------------------------------------------------------------------------------- |
| porter  | Yes     | Applies Porter stemming. "running" matches "run." Best for natural language.      |
| trigram | No      | Overlapping 3-character windows. "config" matches "configuration." Best for code. |

## Keyword match mode

The `keyword_match_mode` field (inside `retrieval_options`) controls how multiple query terms are combined.

| Value | Default | Description                                                   |
| ----- | ------- | ------------------------------------------------------------- |
| and   | Yes     | All query terms must appear. Higher precision, fewer results. |
| or    | No      | Any query term can match. Higher recall, more results.        |

You can override `keyword_match_mode` per request:

TypeScript

```
const instance = env.AI_SEARCH.get("my-instance");
const results = await instance.search({  messages: [{ role: "user", content: "What is Cloudflare?" }],  ai_search_options: {    retrieval: {      keyword_match_mode: "or",    },  },});
```

## Limits

Instances with keyword search enabled support up to 500,000 files per instance on the Workers Paid tier, compared to 1,000,000 for vector-only instances. Refer to [Limits and pricing](https://developers.cloudflare.com/ai-search/platform/limits-pricing/) for the full list of limits.

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