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

# Connect PubChem with No Authentication – StackOne Hub

> Link a PubChem account in the StackOne Hub using No Authentication. End-user guide to authorize the integration and start using PubChem actions.

## Connect without authentication

PubChem's web services take **no credentials**, so there is nothing to obtain from NCBI. Create the connection and StackOne starts calling PubChem straight away.

**1. Create the connection**

Choose the **No Authentication** option and create the connection in StackOne Hub. There are no fields to fill in.

**2. Know the limits**

PubChem limits requests to 5 per second per IP address and throttles or blocks heavy use with a 503 error.

<ul>
  <li>The Entrez actions call NCBI's E-utilities, which allow 3 requests per second per IP address without an API key and 10 with one. To use your own key, create the connection with the **NCBI API Key** option instead.</li>
  <li>PubChem data licences vary by contributing source. Annotations carry the licence of each source in `LicenseNote` and `LicenseURL`.</li>
  <li>When you publish results that use PubChem, cite: Kim S, Chen J, Cheng T, et al. PubChem 2025 update. Nucleic Acids Res. 2025;53(D1):D1516-D1525. doi:10.1093/nar/gkae1059. Cite a single record by its URL, for example [https://pubchem.ncbi.nlm.nih.gov/compound/2244](https://pubchem.ncbi.nlm.nih.gov/compound/2244).</li>
</ul>

## Linking the Account from the Hub

**1. Navigate to the Hub**

Use one of the three [Linking Account Methods](https://docs.stackone.com/connect/managing-connectors/linking-accounts.md) to access the Hub.

**2. Connect**

<ul>
  <li>Click **Connect**</li>
  <li>If applicable, the provider will redirect you to a sign-in or authorization page. Complete the provider's authorization flow.</li>
  <li>Once authorization is successful, you will see a confirmation popup</li>
</ul>

If the account linking is successful, you will see the newly linked account on your [Accounts](https://app.stackone.com/accounts) page.


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