Embedding Models for Search & Science

BAAI (Beijing Academy of AI) open-weight English embedding model with 335M parameters. Returns 1024-dim vectors and was a top MTEB English retrieval model on release. The v1.5 update improved similarity distribution so it works well without a query instruction prefix for symmetric tasks. A widely used open alternative to hosted embeddings.

BAAI multilingual embedding model covering 100+ languages with an 8192-token context. M3 stands for its multi-functionality (dense, sparse and ColBERT-style multi-vector retrieval), multilinguality and multi-granularity over long documents. Returns 1024-dim dense vectors and is a strong open choice for cross-lingual and long-text retrieval.

Meta AI 650M-parameter protein language model trained on UniRef50 sequences. Feed it an amino-acid sequence and the per-residue hidden states act as learned protein embeddings, used for structure prediction, variant-effect and function tasks. This 33-layer checkpoint is the common balance of quality and cost in the ESM-2 family.

Nomic AI open embedding model with a fully reproducible training pipeline (open weights, data and code). Supports an 8192-token context and Matryoshka representation learning, so you can truncate the 768-dim output down to 64 dims with graceful quality loss. Uses task prefixes like search_query and search_document.

OpenAI's highest-quality embedding model. Returns 3072-dim vectors by default and supports reducing dimensions via the dimensions parameter. Outperforms text-embedding-3-small and the older ada-002 on MTEB and multilingual MIRACL retrieval benchmarks, for cases where accuracy matters more than cost.

OpenAI's small, low-cost embedding model. Returns 1536-dim vectors by default and supports shortening output dimensions via the dimensions parameter without retraining. Replaced text-embedding-ada-002 with better retrieval quality at a fraction of the price, and is the default choice for general-purpose semantic search and RAG.

Sentence-transformers model fine-tuned from Microsoft PubMedBERT on PubMed title-abstract pairs by the NeuML team. Produces 768-dim sentence embeddings tuned for biomedical semantic search and similarity, and is the embedding backbone behind the paperai and txtai medical search tools.

AllenAI document-level embedding model for scientific papers. Built on SciBERT and trained on the citation graph so that papers citing each other land close together. Feed it a title plus abstract and it returns one 768-dim vector per paper, useful for recommendation, clustering and citation-based retrieval.

Voyage's general-purpose embedding model. 1024 dims, 32k context, strong retrieval performance.

DMIS-Lab (Korea University) BERT-base initialized from English BERT and further pretrained on PubMed abstracts. Used as a feature extractor it yields 768-dim contextual embeddings tuned for biomedical text mining tasks such as NER, relation extraction and biomedical question answering.

Microsoft BiomedBERT (formerly PubMedBERT) pretrained from scratch on PubMed abstracts with a domain-specific vocabulary, rather than adapting a general model. As a feature extractor it gives 768-dim biomedical embeddings and set the original state of the art on the BLURB biomedical NLP benchmark.

Cohere's multilingual embedding model. Supports 100+ languages with separate search and classification modes.

Alibaba (Tongyi Lab) general text embedding model. The v1.5 release extends the context to 8192 tokens and returns 1024-dim vectors, scoring competitively on MTEB while handling much longer inputs than typical 512-token encoders. A practical open model when documents exceed the usual short-context limit.

Jina's frontier multilingual embedding model. 570M params, 8192 ctx, 89 languages, Matryoshka dims 128-1024.

Microsoft E5 multilingual embedding model with 560M parameters, initialized from XLM-RoBERTa-large and trained with weakly supervised contrastive learning. Covers around 100 languages and returns 1024-dim vectors. It expects query: and passage: prefixes on inputs and is a popular open model for multilingual semantic search.

Mixedbread's open-source 335M embedding model. Top MTEB benchmark for English retrieval at release.

AllenAI BERT-base pretrained from scratch on 1.14M scientific papers (mostly biomedical and computer science) with its own scientific WordPiece vocabulary. Used as a feature extractor it gives 768-dim contextual embeddings tuned to scientific text, outperforming general BERT on tasks like NER and relation extraction in research corpora.

Voyage's code-specialized embedding model. Up to 32k context, Matryoshka 256-2048 dims, int8/binary support.