zerank
ZeroEntropyZeroEntropy's reranker line. zerank-2 is a 4B Qwen3-derived cross-encoder with a 32K context, trained through a multi-stage pipeline that models query-document relevance as adjusted Elo ratings; its card reports an average 0.6714 NDCG@10 across seven domains against 0.5847 for Cohere rerank-3.5. The earlier zerank-1 and zerank-1-small ship alongside it. Notion acquired ZeroEntropy in July 2026 and the weights were released under Apache 2.0.
The hosted ZeroEntropy API was sunset on 2026-09-04; the weights themselves are unaffected and remain on the Hub, so this entry carries no end-of-life mark.
Openness
3 high confidence- weights
- open(Apache-2.0 ungated safetensors for zerank-1, zerank-1-small and zerank-2)
- data
- closed(the Elo-based relevance pipeline is described in arXiv 2509.12541
- code
- closed(no training or model repository
- license
- Apache-2.0(OSI)
Both zerank-2 and the earlier zerank-1 line are released under Apache-2.0, confirmed in the card and in ZeroEntropy's announcement of the Notion acquisition, which states that all its models are now open source under Apache-2.0. Neither the training data nor any training or model repository is released, so the release stays open weights rather than open source.
- https://huggingface.co/zeroentropy/zerank-1-reranker/raw/main/README.md recorded 2026-10-20
Front matter for zerank-1 also reads license: apache-2.0, confirming the terms are consistent across the distributed SKUs rather than new with zerank-2.
- https://huggingface.co/zeroentropy/zerank-2-reranker/raw/main/README.md recorded 2026-10-20
Front matter reads license: apache-2.0, base_model Qwen/Qwen3-4B; the Model Details table records License Apache-2.0 and the closing License section repeats it. Training is described as a multi-stage Elo-rating pipeline with a link to arXiv 2509.12541; no corpus or training code is offered.
- https://zeroentropy.dev/articles/zeroentropy-is-joining-notion/ recorded 2026-10-20
ZeroEntropy announcement dated 2026-07-24: "ZeroEntropy has been acquired by Notion", "All of our models are now fully open-source under Apache 2.0", and all ZeroEntropy products remain supported until September 4th, 2026 after which they are sunset.
Adoption
3 high confidenceAdoption is measured as Hugging Face downloads across the zerank line, almost all of it for zerank-2, with much smaller shares for zerank-1-small and zerank-1.
- https://huggingface.co/api/models/zeroentropy/zerank-2-reranker recorded 2026-09-11
downloads: 644922; gated: false; private: false; license apache-2.0 for zeroentropy/zerank-2-reranker.
Capability
4 medium confidenceZerank-2 is a current 4B model that beats the named proprietary rerankers on ZeroEntropy's own seven-domain suite, putting it at the frontier alongside jina-reranker, the other current-generation line here. Confidence stays medium because that evaluation is a vendor-built suite with no public leaderboard behind it, unlike BEIR or MMTEB.
- https://huggingface.co/zeroentropy/zerank-2-reranker/raw/main/README.md recorded 2026-09-11
Evaluations table gives zerank-2 an average NDCG@10 of 0.6714 across seven domains against 0.6456 for zerank-1, 0.5999 for Gemini 2.5 Flash listwise, 0.5847 for Cohere rerank-3.5 and 0.4509 for the OpenAI embedding retriever alone; 4B parameters, 32,768-token context.
Verified 2026-09-11