# Authentication

OpenAlex data is free, and so is casual use of the API — you can make basic queries with no key at all. To use the API at any real scale, though, you'll want a **free API key**: it raises your daily budget 10× and lets you track your usage. This page covers getting a key, sending it, and staying inside the rate limits. For **what the API costs** and how billing works — that's a separate concern — see [Pricing](/access/pricing/), with worked numbers on the [Example costs](/access/example-costs/) page.

## Getting an API key

It's free. [Make an account](https://openalex.org/) (about 30 seconds) and copy your key from [openalex.org/settings/api](https://openalex.org/settings/api).

## Sending your key

Add it as an `api_key` query parameter:

```bash
curl "https://api.openalex.org/works?api_key=YOUR_KEY"
```

…or send it as a bearer token in the `Authorization` header:

```bash
curl -H "Authorization: Bearer YOUR_KEY" "https://api.openalex.org/works"
```

Both work identically. The [openalex.org](https://openalex.org) website runs on this same API, so anonymous browsing draws from the keyless budget; sign in and it uses your own key.

## Rotating your key

You can replace your key with a new one anytime in [Settings → API key](https://openalex.org/settings/api). When you rotate, you choose when the old key stops working:

- **Immediately** (the default) — the old key dies on the spot. The right choice when a key has leaked.
- **In 24 hours** or **in 7 days** — both keys work during the window, so you can deploy the new key to your systems with no downtime. The old key keeps its normal limits, then stops for good. If you discover a leak mid-window, the **Expire now** button kills the old key early.

Organization keys work the same way, from the organization's API settings. One thing to know about personal keys: your key is also your openalex.org sign-in credential, so rotating it logs you out on your other browsers and devices right away — the grace window applies to API requests only.

## Rate limits

Basic use is free and generous, and a free key gives you 10× the keyless budget; you can raise it further with a [paid plan](/access/pricing/). Two things return `429 Too Many Requests`: exceeding your daily budget, or making more than **100 requests per second**. For the budget numbers themselves — and what typical activity actually uses — see [Example costs](/access/example-costs/).

Individual queries also have hard limits:

| Limit | Value |
|-------|-------|
| OR values per filter | 100 |
| `per_page` maximum | 100 |
| `sample` maximum | 10,000 |
| Basic paging limit | 10,000 results |

To retrieve more than 10,000 results, use [cursor paging](/api/paging/#cursor-paging).

## Keeping tabs on your usage

Every response carries headers and a `meta` block showing where you stand:

| Header | Description |
|--------|-------------|
| `X-RateLimit-Limit` | Your total daily budget |
| `X-RateLimit-Remaining` | Remaining for today |
| `X-RateLimit-Credits-Used` | Cost of this request |
| `X-RateLimit-Reset` | Seconds until reset (midnight UTC) |

The [`meta`](/api/#response-format) object also reports the cost of the call and the total result count, so you can estimate a full paginated pull before committing to it. For a running total, check the [usage dashboard](https://openalex.org/settings/usage) (the battery icon in the lower-left of [openalex.org](https://openalex.org)), or query it programmatically:

```bash
curl "https://api.openalex.org/rate-limit?api_key=YOUR_KEY"
```

## Best practices

- Use `per_page=100` to get more per request — it makes your budget go much further.
- Batch ID lookups with the [OR syntax](/api/filtering/#addition-or) (up to 100 values per filter).
- Use [`select=`](/api/selecting-fields/) to return only the fields you need, for faster responses.
- Implement [exponential backoff](/api/errors/#retry-logic) when you hit a `429`.
- The API is plain GET requests, so you can test any query in your browser — a JSON formatter extension ([JSONVue](https://chrome.google.com/webstore/detail/jsonvue/chklaanhfefbnpoihckbnefhakgolnmc) for Chrome, [JSONView](https://addons.mozilla.org/en-US/firefox/addon/jsonview) for Firefox) makes responses easier to read.