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

# Instant Classification API

> Classify any company by description or website. Get RTICs, RSICs, RNAICs, SICs, and similar companies in a single call.

Send a company description or a website URL and get back real-time industrial classifications across multiple taxonomies, plus a list of similar companies.

## What you get back

A single `POST` request returns:

| Field                 | What it is                                                                                                                                       |
| --------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------ |
| **RTICs**             | Real-Time Industrial Classifications — The Data City's proprietary codes that classify companies by what they actually do, updated continuously. |
| **RSICs**             | Real-time SIC codes — SIC codes refined with live data rather than the static codes on Companies House.                                          |
| **RNAICs**            | Real-time NAICS codes — the North American industry classification equivalent, built the same way as RSICs.                                      |
| **SICs**              | Standard Industrial Classification codes — the statutory UK codes registered at Companies House.                                                 |
| **Similar companies** | Companies with comparable business activities, ranked by similarity score.                                                                       |

Most classifications carry a match score, so you can decide how much to trust each result. See the [response reference](/instant-classification/guides/response-reference) for what every field contains.

## Who it's for

Use this API when you need to classify companies programmatically — for lead enrichment, portfolio tagging, market sizing, or compliance screening.

## How to get started

<CardGroup cols={2}>
  <Card title="Quickstart" icon="rocket" href="/instant-classification/guides/quickstart">
    Sign up and classify your first company in under five minutes.
  </Card>

  <Card title="Authentication" icon="key" href="/instant-classification/guides/authentication">
    OAuth2 password flow — get a JWT, use a Bearer header.
  </Card>

  <Card title="Response reference" icon="brackets-curly" href="/instant-classification/guides/response-reference">
    Every field in the response, and when it's empty.
  </Card>

  <Card title="Errors" icon="triangle-exclamation" href="/instant-classification/guides/errors">
    Every error code, what it means, and what to do about it.
  </Card>

  <Card title="Rate limits & quotas" icon="gauge-high" href="/instant-classification/guides/rate-limits">
    Free-tier usage quota and per-minute rate limits.
  </Card>
</CardGroup>

## Base URL

```text theme={null}
https://instant-classification-api.thedatacity.com/api/v1
```

All endpoints sit under `/api/v1`. The interactive playground on each endpoint page lets you paste your token and send live requests.

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