> ## Documentation Index
> Fetch the complete documentation index at: https://developers.openalex.org/llms.txt
> Use this file to discover all available pages before exploring further.

# Filter

> Narrow down results to entities that match specific conditions

Filters narrow your results to entities matching specific conditions. Use the `filter` parameter with attribute-value pairs:

```
filter=attribute:value,attribute2:value2
```

<Note>
  Filters are case-insensitive.
</Note>

## Examples

<CodeGroup>
  ```bash Works by type theme={"dark"}
  curl "https://api.openalex.org/works?filter=type:book"
  ```

  ```bash Authors by ORCID status theme={"dark"}
  curl "https://api.openalex.org/authors?filter=has_orcid:true,works_count:>100"
  ```

  ```bash Sources with many works theme={"dark"}
  curl "https://api.openalex.org/sources?filter=works_count:>1000"
  ```
</CodeGroup>

## Logical expressions

### Inequality

For numerical filters, use `<` and `>` for inequalities:

```bash theme={"dark"}
# Sources hosting more than 1000 works
https://api.openalex.org/sources?filter=works_count:>1000
```

Some attributes have convenience filters like `from_publication_date` and `to_publication_date`:

```bash theme={"dark"}
# Works published between Jan 1-26, 2022
https://api.openalex.org/works?filter=from_publication_date:2022-01-01,to_publication_date:2022-01-26
```

### Negation (NOT)

Prepend `!` to negate any filter:

```bash theme={"dark"}
# All institutions except those in the US
https://api.openalex.org/institutions?filter=country_code:!us
```

### Intersection (AND)

Comma-separated filters are combined with AND:

```bash theme={"dark"}
# Works cited more than once AND open access
https://api.openalex.org/works?filter=cited_by_count:>1,is_oa:true
```

For AND within a single attribute, repeat the filter or use `+`:

<CodeGroup>
  ```bash Repeating filters theme={"dark"}
  # Works with authors from France AND UK
  https://api.openalex.org/works?filter=institutions.country_code:fr,institutions.country_code:gb
  ```

  ```bash Using + symbol theme={"dark"}
  # Works with authors from France AND UK
  https://api.openalex.org/works?filter=institutions.country_code:fr+gb
  ```
</CodeGroup>

<Note>
  The `+` syntax doesn't work for search filters, boolean filters, or numeric filters.
</Note>

### Addition (OR)

Use the pipe `|` to match any of multiple values:

```bash theme={"dark"}
# Works with authors from France OR UK
https://api.openalex.org/works?filter=institutions.country_code:fr|gb
```

This is efficient for retrieving many records by ID at once:

```bash theme={"dark"}
# Get two works by DOI in one request
https://api.openalex.org/works?filter=doi:https://doi.org/10.1371/journal.pone.0266781|https://doi.org/10.1371/journal.pone.0267149
```

<Warning>
  **OR limit:** You can combine up to 100 values with `|` in a single filter. Use `per_page=100` to get all results.
</Warning>

<Warning>
  **OR works within a filter, not between filters.** This will return an error:

  ```bash theme={"dark"}
  # INVALID: OR between different filters
  https://api.openalex.org/works?filter=institutions.country_code:fr|primary_location.source.issn:0957-1558
  ```
</Warning>

## Filter by saved collection

The `collection:` filter narrows results to the entities you've saved in one
of your [collections](/guides/collections). It's available on every entity
type collections support — `/works`, `/authors`, `/sources`, `/institutions`,
`/topics`, `/sdgs`, `/funders`, `/publishers`, `/keywords`, `/concepts` —
and requires a `Bearer` API key or JWT for the user who owns the collection.

```bash theme={"dark"}
GET https://api.openalex.org/works?filter=collection:col_beNWUTw6qY
Authorization: Bearer <jwt>
```

Negation with `!` is supported, and `collection:` combines with any other
filter. One `collection:` filter is allowed per request — see the
[Collections guide](/guides/collections) for the full set of caps and behaviors.

## Available filters by entity

Each entity type has its own set of filterable fields. See the API reference for complete filter lists:

| Entity                                      | Filters                                                                                                                                  |
| ------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------- |
| [Works](/api-reference/works)               | `publication_year`, `type`, `open_access.is_oa`, `author.id`, `institutions.id`, `cited_by_count`, `doi`, `has_abstract`, and \~150 more |
| [Authors](/api-reference/authors)           | `has_orcid`, `last_known_institutions.id`, `works_count`, `cited_by_count`, `orcid`                                                      |
| [Sources](/api-reference/sources)           | `is_oa`, `is_in_doaj`, `type`, `country_code`, `host_organization`, `issn`                                                               |
| [Institutions](/api-reference/institutions) | `country_code`, `type`, `is_global_south`, `continent`, `ror`, `has_ror`                                                                 |
| [Topics](/api-reference/topics)             | `domain.id`, `field.id`, `subfield.id`, `works_count`                                                                                    |
| [Keywords](/api-reference/keywords)         | `works_count`, `cited_by_count`                                                                                                          |
| [Publishers](/api-reference/publishers)     | `country_codes`, `hierarchy_level`, `ror`, `parent_publisher`                                                                            |
| [Funders](/api-reference/funders)           | `country_code`, `is_global_south`, `continent`, `ror`, `awards_count`                                                                    |

<Info>
  **Looking for text search?** Filters match exact values. For full-text search in titles, abstracts, and other fields, see [Searching](/guides/searching).
</Info>