### What are the API request limits? A single IP address can only make a certain number of API requests per day, depending on the presence of a valid API key. Default API daily limits: - Key: 10,000 - No Key: 300 These limits are [per user IP address, per-day, with some exceptions][1]. <br> ### When should I use a key? The `No Key` limit is meant for light experimentation and simple development work. The instant you need the higher limit, it is acceptable to [register for a key][2]. Your application does not need to be in a releasable — even an alpha — state. Remember to [update your application registration][3] when you do release your app. <br> ### How do I use the key? For `GET` requests (everything that does not write), [**Add it as a query parameter**][4] -- EG `...&key=abcxyz123` -- (*not* as a header) to the requested URL. <br> ### I'm building a library, should I include a key? No, your library should instead take a key to use at initialization. Remember that using a revoked or invalid key on a request will cause that request to not be completed. Consequently, an abusive application using your library could result in all legitimate applications also using your library being banned from the API. For development purposes it's fine to register for an API key and use it in, say, a test suite or demo application. <br> ### What should I do if I need more requests per day? Certain types of applications — services and websites, to name two — can legitimately have much higher per-day request requirements than typical applications. If you can demonstrate a need for a higher request quota, contact us. However, the `Key` limit should be sufficient for development, so please only request an increased quota when your application is live and has a non-trivial number of users. <br> ### What if I share an IP with another [app]? You should use the [authentication feature][5] to acquire a `no_expiry` access_token tied to your account, and use it for all requests. [1]: https://api.stackexchange.com/docs/throttle [2]: https://stackapps.com/apps/oauth/register [3]: https://stackapps.com/apps/oauth/ [4]: https://stackapps.com/a/4702 [5]: https://api.stackexchange.com/docs/authentication