# Foundation Models (LLMs): the tools companies use

160 companies on usedby use at least one of the 7 tools in this category with a public customer. Claude leads with 73 companies. Counts are of companies on usedby, not of the whole market. Latest check 2026-10-08: 113 of 183 public lines checked.

> Large Language Models available via API

Family: [Engineering & Data](https://www.usedby.ai/tools/category/engineering-data.md)

## Ranking

Public customers count every public line, job-post signals included; ties share a rank.

| Rank | Tool | Public customers | Confirmed | Observed | Signals |
|---|---|---|---|---|---|
| 1 | [Claude](https://www.usedby.ai/tools/claude.md) | 73 | 16 | 32 | 25 |
| 2 | [ChatGPT](https://www.usedby.ai/tools/chatgpt.md) | 40 | 0 | 35 | 5 |
| 3 | [Mistral](https://www.usedby.ai/tools/mistral.md) | 37 | 34 | 3 | 0 |
| 4 | [Cohere](https://www.usedby.ai/tools/cohere.md) | 23 | 8 | 15 | 0 |
| 5 | [OpenAI API](https://www.usedby.ai/tools/openai-api.md) | 5 | 3 | 1 | 1 |
| 6 | [Sakana AI](https://www.usedby.ai/tools/sakana-ai.md) | 3 | 3 | 0 | 0 |
| 7 | [Gemini](https://www.usedby.ai/tools/gemini.md) | 2 | 0 | 0 | 2 |

Tools in this category without a public customer yet: [Poolside](https://www.usedby.ai/tools/poolside.md).

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Source: https://www.usedby.ai/tools/category/foundation-models-llms · How we check: https://www.usedby.ai/methodology