Encoder-only vs decoder-only vs encoder-decoder Transformers?

Encoder-only vs decoder-only vs encoder-decoder Transformers?medium

Type: conceptual
Topic: encoder-only-vs-decoder-only-vs-encoder-decoder-transforme
Frequency: common
Tags: deep-learning, encoder, only, decoder

Answer

Encoder-only (BERT): bidirectional, best for classification, extraction, embeddings.

Explanation

Encoder-only (BERT): bidirectional, best for classification, extraction, embeddings. Decoder-only (GPT, Claude, LLaMA): autoregressive, best for generation and chat. Encoder-decoder (T5, BART): encoder processes input, decoder generates — best for seq2seq (translation, summarization). For RAG generation, decoder-only LLMs are standard; for embedding/retrieval, encoder-only models.

Follow-upWhen would you choose one approach over the other?