Cheméo API

A free account gives you an API key, from your profile page. The API returns the same property values you see on the site, each with its own source, so for every number you know where it came from. It is rate limited to 120 requests per minute per key, with a short burst of up to 30. If you use the data you must cite Cheméo: for a paper, Cheméo, chemical and physical properties (https://www.chemeo.com). Bulk access exists, but it is a conversation with us, not a self-service endpoint.

Getting started

The key follows the bearer format. Pass it in the Authorization header. To get a compound by its Cheméo id:

curl -H "Authorization: Bearer YOUR_API_KEY" \
     https://www.chemeo.com/api/v1/cid/26-454-9

What you get back

The compound is returned under the comp key:

{
  "comp": {
    "id": "26-454-9",
    "compound": "octapentacontane",
    "cas": "7667-78-9",
    "inchikey": "HDKSWQPFGWHOIA-UHFFFAOYSA-N",
    "formula": "C58H118",
    "mw": 815.5575,
    ....
  }
}

The response carries more than the identifiers shown above: the full set of property values, each with its source, so you can tell measured data from a prediction and follow every value back to the paper or database it came from. The endpoints for search, mixtures and property prediction are listed in the reference below.

Rate limits

Requests are limited per key: a burst of up to 30, then a sustained 120 per minute (2 per second). Every response carries the standard RateLimit headers with your remaining budget. Going over the limit returns 429 Too Many Requests with a Retry-After header telling you how long to wait. If you need a higher limit, ask us.

Reference

• Interactive API documentation, where you can enter your key and run each call in the browser.
• Machine-readable API description (OpenAPI/Swagger), for tools and agents.
• Terms and citation wording, short and in plain language.

Bulk or institutional access

The database is free to search and to use value by value, but it is not for bulk download. If you need the full dataset, or a higher rate limit for an institution, write to us at support@ceondo.com and we will sort something out. We want the data used, not abused.