Cohere Rerank

Hosted API · Cohere

Cohere Rerank was one of the first commercial reranking APIs and remains among the most widely deployed. The current generation — rerank-v3.5 — delivers strong multilingual precision on BEIR benchmarks, a clean REST + SDK interface, and a free tier generous enough for development and low-volume production.

Available models

Use rerank-v3.5 by default. Downgrade to rerank-english-v3.0 only if you're English-only and every millisecond matters.

Pricing

Check the official Cohere pricing page for current rates — figures above may be outdated.

Quick start

Python

pip install cohere

import cohere

co = cohere.Client("YOUR_API_KEY")

query = "How do I add reranking to my RAG pipeline?"
documents = [
    "Rerankers score each query-passage pair jointly with a cross-encoder.",
    "BM25 is a classical keyword-based retrieval method.",
    "London is the capital of the United Kingdom.",
    "Two-stage retrieval: retrieve 50 candidates, rerank to top 5.",
]

results = co.rerank(
    model="rerank-v3.5",
    query=query,
    documents=documents,
    top_n=3,
)

for r in results.results:
    print(f"{r.relevance_score:.4f}  {documents[r.index][:80]}")

Node.js

import Cohere from "cohere-ai";
const co = new Cohere.Client({ token: "YOUR_API_KEY" });

const result = await co.rerank({
  model: "rerank-v3.5",
  query: "How do I add reranking to my RAG pipeline?",
  documents: ["...", "..."],
  topN: 3,
});

result.results.forEach((r) => console.log(r.relevanceScore, documents[r.index]));

REST (curl)

curl https://api.cohere.com/v2/rerank \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "rerank-v3.5",
    "query": "How do I add reranking to my RAG pipeline?",
    "documents": ["Rerankers score query-passage pairs...", "BM25 is..."],
    "top_n": 3
  }'

Pros and cons

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